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NERSC Staff Publications & Presentations

Journal Article

Smith, M., Sullivan, M., D'Andrea, C. B., Castander, F. J., Casas, R., Prajs, S., Papadopoulos, A., Nichol, R. C., Karpenka, N. V., Bernard, S. R., Brown, P., Cartier, R., Cooke, J., Curtin, C., Davis, T. M., Finley, D. A., Foley, R. J., Gal-Yam, A., Goldstein, D. A., González-Gaitán, S., Gupta, R. R., Howell, D. A., Inserra, C., Kessler, R., Lidman, C., Marriner, J., Nugent, P., Pritchard, T. A., Sako, M., Smartt, S., Smith, R. C., Spinka, H., Thomas, R. C., Wolf, R. C., Zenteno, A., Abbott, T. M. C., Benoit-Lévy, A., Bertin, E., Brooks, D., Buckley-Geer, E., Carnero Rosell, A., Carrasco Kind, M., Carretero, J., Crocce, M., Cunha, C. E., da Costa, L. N., Desai, S., Diehl, H. T., Doel, P., Estrada, J., Evrard, A. E., Flaugher, B., Fosalba, P., Frieman, J., Gerdes, D. W., Gruen, D., Gruendl, R. A., James, D. J., Kuehn, K., Kuropatkin, N., Lahav, O., Li, T. S., Marshall, J. L., Martini, P., Miller, C. J., Miquel, R., Nord, B., Ogando, R., Plazas, A. A., Reil, K., Romer, A. K., Roodman, A., Rykoff, E. S., Sanchez, E., Scarpine, V., Schubnell, M., Sevilla-Noarbe, I., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M. E. C., Tarle, G., Walker, A. R., Wester, W.,"DES14X3taz: A Type I Superluminous Supernova Showing a Luminous, Rapidly Cooling Initial Pre-peak Bump",The Astrophysical Journal Letters,2016,doi: 10.3847/2041-8205/818/1/L8

We present DES14X3taz, a new hydrogen-poor superluminous supernova (SLSN-I) discovered by the Dark Energy Survey (DES) supernova program, with additional photometric data provided by the Survey Using DECam for Superluminous Supernovae. Spectra obtained using Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy on the Gran Telescopio CANARIAS show DES14X3taz is an SLSN-I at z = 0.608. Multi-color photometry reveals a double-peaked light curve: a blue and relatively bright initial peak that fades rapidly prior to the slower rise of the main light curve. Our multi-color photometry allows us, for the first time, to show that the initial peak cools from 22,000 to 8000 K over 15 rest-frame days, and is faster and brighter than any published core-collapse supernova, reaching 30% of the bolometric luminosity of the main peak. No physical 56Ni-powered model can fit this initial peak. We show that a shock-cooling model followed by a magnetar driving the second phase of the light curve can adequately explain the entire light curve of DES14X3taz. Models involving the shock-cooling of extended circumstellar material at a distance of ≃400 {\text{}}{R}⊙ are preferred over the cooling of shock-heated surface layers of a stellar envelope. We compare DES14X3taz to the few double-peaked SLSN-I events in the literature. Although the rise times and characteristics of these initial peaks differ, there exists the tantalizing possibility that they can be explained by one physical interpretation.

Parrent, J. T., Howell, D. A., Fesen, R. A., Parker, S., Bianco, F. B., Dilday, B., Sand, D., Valenti, S., Vinkó, J., Berlind, P., Challis, P., Milisavljevic, D., Sanders, N., Marion, G. H., Wheeler, J. C., Brown, P., Calkins, M. L., Friesen, B., Kirshner, R., Pritchard, T., Quimby, R., Roming, P.,"Comparative analysis of SN 2012dn optical spectra: days -14 to +114",Monthly Notices of the Royal Astronomical Society,January 29, 2016,457:3702-3723,doi: 10.1093/mnras/stw239

SN 2012dn is a super-Chandrasekhar mass candidate in a purportedly normal spiral (SAcd) galaxy, and poses a challenge for theories of type Ia supernova diversity. Here we utilize the fast and highly parametrized spectrum synthesis tool, SYNAPPS, to estimate relative expansion velocities of species inferred from optical spectra obtained with six facilities. As with previous studies of normal SN Ia, we find that both unburned carbon and intermediate-mass elements are spatially coincident within the ejecta near and below 14 000 km s−1. Although the upper limit on SN 2012dn's peak luminosity is comparable to some of the most luminous normal SN Ia, we find a progenitor mass exceeding ∼1.6 M is not strongly favoured by leading merger models since these models do not accurately predict spectroscopic observations of SN 2012dn and more normal events. In addition, a comparison of light curves and host-galaxy masses for a sample of literature and Palomar Transient Factory SN Ia reveals a diverse distribution of SN Ia subtypes where carbon-rich material remains unburned in some instances. Such events include SN 1991T, 1997br, and 1999aa where trace signatures of C III at optical wavelengths are presumably detected.

Baron, E., Hoeflich, P., Friesen, B., Sullivan, M., Hsiao, E., Ellis, R. S., Gal-Yam, A., Howell, D. A., Nugent, P. E., Dominguez, I., Krisciunas, K., Phillips, M. M., Suntzeff, N., Wang, L., and Thomas, R. C.,"Spectral models for early time SN 2011fe observations",Monthly Notices of the Royal Astronomical Society,2015,454:2549,doi: 10.1093/mnras/stv1951

We use observed UV through near-IR spectra to examine whether SN 2011fe can be understood in the framework of Branch-normal Type Ia supernovae (SNe Ia) and to examine its individual peculiarities. As a benchmark, we use a delayed-detonation model with a progenitor metallicity of Z/20. We study the sensitivity of features to variations in progenitor metallicity, the outer density profile, and the distribution of radioactive nickel. The effect of metallicity variations in the progenitor have a relatively small effect on the synthetic spectra. We also find that the abundance stratification of SN 2011fe resembles closely that of a delayed-detonation model with a transition density that has been fit to other Branch-normal SNe Ia. At early times, the model photosphere is formed in material with velocities that are too high, indicating that the photosphere recedes too slowly or that SN 2011fe has a lower specific energy in the outer ≈0.1 M than does the model. We discuss several explanations for the discrepancies. Finally, we examine variations in both the spectral energy distribution and in the colours due to variations in the progenitor metallicity, which suggests that colours are only weak indicators for the progenitor metallicity, in the particular explosion model that we have studied. We do find that the flux in the U band is significantly higher at maximum light in the solar metallicity model than in the lower metallicity model and the lower metallicity model much better matches the observed spectrum.

Fakhouri, H. K., Boone, K., Aldering, G., Antilogus, P., Aragon, C., Bailey, S., Baltay, C., Barbary, K., Baugh, D., Bongard, S., Buton, C., Chen, J., Childress, M., Chotard, N., Copin, Y., Fagrelius, P., Feindt, U., Fleury, M., Fouchez, D., Gangler, E., Hayden, B., Kim, A. G., Kowalski, M., Leget, P.-F., Lombardo, S., Nordin, J., Pain, R., Pecontal, E., Pereira, R., Perlmutter, S., Rabinowitz, D., Ren, J., Rigault, M., Rubin, D., Runge, K., Saunders, C., Scalzo, R., Smadja, G., Sofiatti, C., Strovink, M., Suzuki, N., Tao, C., Thomas, R. C., and Weaver, B. A.,"Improving Cosmological Distance Measurements Using Twin Type Ia Supernovae",The Astrophysical Journal,2015,815:58,doi: 10.1088/0004-637X/815/1/58

We introduce a method for identifying “twin” Type Ia supernovae (SNe Ia) and using them to improve distance measurements. This novel approach to SN Ia standardization is made possible by spectrophotometric time series observations from the Nearby Supernova Factory (SNfactory). We begin with a well-measured set of SNe, find pairs whose spectra match well across the entire optical window, and then test whether this leads to a smaller dispersion in their absolute brightnesses. This analysis is completed in a blinded fashion, ensuring that decisions made in implementing the method do not inadvertently bias the result. We find that pairs of SNe with more closely matched spectra indeed have reduced brightness dispersion. We are able to standardize this initial set of SNfactory SNe to 0.083 ± 0.012 mag, implying a dispersion of 0.072 ± 0.010 mag in the absence of peculiar velocities. We estimate that with larger numbers of comparison SNe, e.g., using the final SNfactory spectrophotometric data set as a reference, this method will be capable of standardizing high-redshift SNe to within 0.06–0.07 mag. These results imply that at least 3/4 of the variance in Hubble residuals in current SN cosmology analyses is due to previously unaccounted-for astrophysical differences among the SNe.

Kessler, R., Marriner, J., Childress, M., Covarrubias, R., D'Andrea, C. B., Finley, D. A., Fischer, J., Foley, R. J., Goldstein, D., Gupta, R. R., Kuehn, K., Marcha, M., Nichol, R. C., Papadopoulos, A., Sako, M., Scolnic, D., Smith, M., Sullivan, M., Wester, W., Yuan, F., Abbott, T., Abdalla, F. B., Allam, S., Benoit-Levy, A., Bernstein, G. M., Bertin, E., Brooks, D., Carnero Rosell, A., Carrasco Kind, M., Castander, F. J., Crocce, M., da Costa, L. N., Desai, S., Diehl, H. T., Eifler, T. F., Fausti Neto, A., Flaugher, B., Frieman, J., Gerdes, D. W., Gruen, D., Gruendl, R. A., Honscheid, K., James, D. J., Kuropatkin, N., Li, T. S., Maia, M. A. G., Marshall, J. L., Martini, P., Miller, C. J., Miquel, R., Nord, B., Ogando, R., Plazas, A. A., Reil, K., Romer, A. K., Roodman, A., Sanchez, E., Sevilla-Noarbe, I., Smith, R. C., Soares-Santos, M., Sobreira, F., Tarle, G., Thaler, J., Thomas, R. C., Tucker, D., and Walker, A. R.,"The Difference Imaging Pipeline for the Transient Search in the Dark Energy Survey",The Astronomical Journal,2015,150:172,doi: 10.1088/0004-6256/150/6/172

We describe the operation and performance of the difference imaging pipeline (DiffImg) used to detect transients in deep images from the Dark Energy Survey Supernova program (DES-SN) in its first observing season from 2013 August through 2014 February. DES-SN is a search for transients in which ten 3 deg2 fields are repeatedly observed in the g, r, i, z passbands with a cadence of about 1 week. The observing strategy has been optimized to measure high-quality light curves and redshifts for thousands of Type Ia supernovae (SNe Ia) with the goal of measuring dark energy parameters. The essential DiffImg functions are to align each search image to a deep reference image, do a pixel-by-pixel subtraction, and then examine the subtracted image for significant positive detections of point-source objects. The vast majority of detections are subtraction artifacts, but after selection requirements and image filtering with an automated scanning program, there are ∼130 detections per deg2 per observation in each band, of which only ∼25% are artifacts. Of the ∼7500 transients discovered by DES-SN in its first observing season, each requiring a detection on at least two separate nights, Monte Carlo (MC) simulations predict that 27% are expected to be SNe Ia or core-collapse SNe. Another ∼30% of the transients are artifacts in which a small number of observations satisfy the selection criteria for a single-epoch detection. Spectroscopic analysis shows that most of the remaining transients are AGNs and variable stars. Fake SNe Ia are overlaid onto the images to rigorously evaluate detection efficiencies and to understand the DiffImg performance. The DiffImg efficiency measured with fake SNe agrees well with expectations from a MC simulation that uses analytical calculations of the fluxes and their uncertainties. In our 8 “shallow” fields with single-epoch 50% completeness depth ∼23.5, the SN Ia efficiency falls to 1/2 at redshift z ≈ 0.7; in our 2 “deep” fields with mag-depth ∼24.5, the efficiency falls to 1/2 at z ≈ 1.1. A remaining performance issue is that the measured fluxes have additional scatter (beyond Poisson fluctuations) that increases with the host galaxy surface brightness at the transient location. This bright-galaxy issue has minimal impact on the SNe Ia program, but it may lower the efficiency for finding fainter transients on bright galaxies.

F. P. An et al. (Daya Bay Collaboration),"New Measurement of Antineutrino Oscillation with the Full Detector Configuration at Daya Bay",Phys. Rev. Lett. 115, 111802,September 11, 2015,Vol. 115, doi: http://dx.doi.org/10.1103/PhysRevLett.115.111802

We report a new measurement of electron antineutrino disappearance using the fully constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9 x 10^5 GW,ton a day, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six radioactive calibration sources reduced the background by a factor of 2 for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission.

Yuan, F., Lidman, C., Davis, T. M., Childress, M., Abdalla, F. B., Banerji, M., Buckley-Geer, E., Carnero Rosell, A., Carollo, D., Castander, F. J., D'Andrea, C. B., Diehl, H. T., Cunha, C. E., Foley, R. J., Frieman, J., Glazebrook, K., Gschwend, J., Hinton, S., Jouvel, S., Kessler, R., Kim, A. G., King, A. L., Kuehn, K., Kuhlmann, S., Lewis, G. F., Lin, H., Martini, P., McMahon, R. G., Mould, J., Nichol, R. C., Norris, R. P., O'Neill, C. R., Ostrovski, F., Papadopoulos, A., Parkinson, D., Reed, S., Romer, A. K., Rooney, P. J., Rozo, E., Rykoff, E. S., Sako, M., Scalzo, R., Schmidt, B. P., Scolnic, D., Seymour, N., Sharp, R., Sobreira, F., Sullivan, M., Thomas, R. C., Tucker, D., Uddin, S. A., Wechsler, R. H., Wester, W., Wilcox, H., Zhang, B., Abbott, T., Allam, S., Bauer, A. H., Benoit-Levy, A., Bertin, E., Brooks, D., Burke, D. L., Carrasco Kind, M., Covarrubias, R., Crocce, M., da Costa, L. N., DePoy, D. L., Desai, S., Doel, P., Eifler, T. F., Evrard, A. E., Fausti Neto, A., Flaugher, B., Fosalba, P., Gaztanaga, E., Gerdes, D., Gruen, D., Gruendl, R. A., Honscheid, K., James, D., Kuropatkin, N., Lahav, O., Li, T. S., Maia, M. A. G., Makler, M., Marshall, J., Miller, C. J., Miquel, R., Ogando, R., Plazas, A. A., Roodman, A., Sanchez, E., Scarpine, V., Schubnell, M., Sevilla-Noarbe, I., Smith, R. C., Soares-Santos, M., Suchyta, E., Swanson, M. E. C., Tarle, G., Thaler, J., and Walker, A. R.,"OzDES multifibre spectroscopy for the Dark Energy Survey: first-year operation and results",Monthly Notices of the Royal Astronomical Society,2015,452:3047,doi: 10.1093/mnras/stv1507

The Australian Dark Energy Survey (OzDES) is a five-year, 100-night, spectroscopic survey on the Anglo-Australian Telescope, whose primary aim is to measure redshifts of approximately 2500 Type Ia supernovae host galaxies over the redshift range 0.1 < z < 1.2, and derive reverberation-mapped black hole masses for approximately 500 active galactic nuclei and quasars over 0.3 < z < 4.5. This treasure trove of data forms a major part of the spectroscopic follow-up for the Dark Energy Survey for which we are also targeting cluster galaxies, radio galaxies, strong lenses, and unidentified transients, as well as measuring luminous red galaxies and emission line galaxies to help calibrate photometric redshifts. Here, we present an overview of the OzDES programme and our first-year results. Between 2012 December and 2013 December, we observed over 10 000 objects and measured more than 6 000 redshifts. Our strategy of retargeting faint objects across many observing runs has allowed us to measure redshifts for galaxies as faint as mr = 25 mag. We outline our target selection and observing strategy, quantify the redshift success rate for different types of targets, and discuss the implications for our main science goals. Finally, we highlight a few interesting objects as examples of the fortuitous yet not totally unexpected discoveries that can come from such a large spectroscopic survey.

Goldstein, D. A., D'Andrea, C. B., Fischer, J. A., Foley, R. J., Gupta, R. R., Kessler, R., Kim, A. G., Nichol, R. C., Nugent, P. E., Papadopoulos, A., Sako, M., Smith, M., Sullivan, M., Thomas, R. C., Wester, W., Wolf, R. C., Abdalla, F. B., Banerji, M., Benoit-Levy, A., Bertin, E., Brooks, D., Carnero Rosell, A., Castander, F. J., da Costa, L. N., Covarrubias, R., DePoy, D. L., Desai, S., Diehl, H. T., Doel, P., Eifler, T. F., Fausti Neto, A., Finley, D. A., Flaugher, B., Fosalba, P., Frieman, J., Gerdes, D., Gruen, D., Gruendl, R. A., James, D., Kuehn, K., Kuropatkin, N., Lahav, O., Li, T. S., Maia, M. A. G., Makler, M., March, M., Marshall, J. L., Martini, P., Merritt, K. W., Miquel, R., Nord, B., Ogando, R., Plazas, A. A., Romer, A. K., Roodman, A., Sanchez, E., Scarpine, V., Schubnell, M., Sevilla-Noarbe, I., Smith, R. C., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M. E. C., Tarle, G., Thaler, J., and Walker, A. R.,"Automated Transient Identification in the Dark Energy Survey",The Astronomical Journal,2015,150:82,doi: 10.1088/0004-6256/150/3/82

We describe an algorithm for identifying point-source transients and moving objects on reference-subtracted optical images containing artifacts of processing and instrumentation. The algorithm makes use of the supervised machine learning technique known as Random Forest. We present results from its use in the Dark Energy Survey Supernova program (DES-SN), where it was trained using a sample of 898,963 signal and background events generated by the transient detection pipeline. After reprocessing the data collected during the first DES-SN observing season (2013 September through 2014 February) using the algorithm, the number of transient candidates eligible for human scanning decreased by a factor of 13.4, while only 1.0% of the artificial Type Ia supernovae (SNe) injected into search images to monitor survey efficiency were lost, most of which were very faint events. Here we characterize the algorithm’s performance in detail, and we discuss how it can inform pipeline design decisions for future time-domain imaging surveys, such as the Large Synoptic Survey Telescope and the Zwicky Transient Facility. An implementation of the algorithm and the training data used in this paper are available at at http://portal.nersc.gov/project/dessn/autoscan.

Daya Bay Collaboration: F.P. An, A.B. Balantekin, H.R. Band, W. Beriguete, et. al,"The Muon System of the Daya Bay Reactor Antineutrino Experiment",Nuclear Instruments and Methods in Physics,August 20, 2015,Volume 7, doi: http://dx.doi.org/10.1016/j.nima.2014.09.070

The Daya Bay experiment consists of functionally identical antineutrino detectors immersed in pools of ultrapure water in three well-separated underground experimental halls near two nuclear reactor complexes. These pools serve both as shields against natural, low-energy radiation, and as water Cherenkov detectors that effciently detect cosmogenic muons using arrays of photomultiplier tubes. Each pool is covered by a plane of resistive plate chambers as an additional means of detecting muons. Design, construction, operation, and performance of these muon detectors are described.

Kim, A. G., Padmanabhan, N., Aldering, G., Allen, S. W., Baltay, C., Cahn, R. N., D'Andrea, C. B., Dalal, N., Dawson, K. S., Denney, K. D., Eisenstein, D. J., Finley, D. A., Freedman, W. L., Ho, S., Holz, D. E., Kasen, D., Kent, S. M., Kessler, R., Kuhlmann, S., Linder, E. V., Martini, P., Nugent, P. E., Perlmutter, S., Peterson, B. M., Riess, A. G., Rubin, D., Sako, M., Suntzeff, N. V., Suzuki, N., Thomas, R. C., Wood-Vasey, W. M., and Woosley, S. E.,"Distance probes of dark energy",Astroparticle Physics,2015,63:2,doi: 10.1016/j.astropartphys.2014.05.007

This document presents the results from the Distances subgroup of the Cosmic Frontier Community Planning Study (Snowmass 2013). We summarize the current state of the field as well as future prospects and challenges. In addition to the established probes using Type Ia supernovae and baryon acoustic oscillations, we also consider prospective methods based on clusters, active galactic nuclei, gravitational wave sirens and strong lensing time delays.

Sasdelli, M., Hillebrandt, W., Aldering, G., Antilogus, P., Aragon, C., Bailey, S., Baltay, C., Benitez-Herrera, S., Bongard, S., Buton, C., Canto, A., Cellier-Holzem, F., Chen, J., Childress, M., Chotard, N., Copin, Y., Fakhouri, H. K., Feindt, U., Fink, M., Fleury, M., Fouchez, D., Gangler, E., Guy, J., Ishida, E. E. O., Kim, A. G., Kowalski, M., Kromer, M., Lombardo, S., Mazzali, P. A., Nordin, J., Pain, R., Pecontal, E., Pereira, R., Perlmutter, S., Rabinowitz, D., Rigault, M., Runge, K., Saunders, C., Scalzo, R., Smadja, G., Suzuki, N., Tao, C., Taubenberger, S., Thomas, R. C., Tilquin, A., and Weaver, B. A.,"A metric space for Type Ia supernova spectra",Monthly Notices of the Royal Astronomical Society,2015,447:1247,doi: 10.1093/mnras/stu2416

We develop a new framework for use in exploring Type Ia supernovae (SNe Ia) spectra. Combining principal component analysis (PCA) and partial least square (PLS) analysis we are able to establish correlations between the principal components (PCs) and spectroscopic/photometric SNe Ia features. The technique was applied to ˜120 SN and ˜800 spectra from the Nearby Supernova Factory. The ability of PCA to group together SNe Ia with similar spectral features, already explored in previous studies, is greatly enhanced by two important modifications: (1) the initial data matrix is built using derivatives of spectra over the wavelength, which increases the weight of weak lines and discards extinction, and (2) we extract time evolution information through the use of entire spectral sequences concatenated in each line of the input data matrix. These allow us to define a stable PC parameter space which can be used to characterize synthetic SN Ia spectra by means of real SN features. Using PLS, we demonstrate that the information from important previously known spectral indicators (namely the pseudo-equivalent width of Si II 5972 Å/Si II 6355 Å and the line velocity of S II 5640 Å/Si II 6355 Å) at a given epoch is contained within the PC space and can be determined through a linear combination of the most important PCs. We also show that the PC space encompasses photometric features like B/V magnitudes, B - V colours and SALT2 parameters c and x1. The observed colours and magnitudes, which are heavily affected by extinction, cannot be reconstructed using this technique alone. All the above-mentioned applications allowed us to construct a metric space for comparing synthetic SN Ia spectra with observations.

Saunders, C., Aldering, G., Antilogus, P., Aragon, C., Bailey, S., Baltay, C., Bongard, S., Buton, C., Canto, A., Cellier-Holzem, F., Childress, M., Chotard, N., Copin, Y., Fakhouri, H. K., Feindt, U., Gangler, E., Guy, J., Kerschhaggl, M., Kim, A. G., Kowalski, M., Nordin, J., Nugent, P., Paech, K., Pain, R., Pecontal, E., Pereira, R., Perlmutter, S., Rabinowitz, D., Rigault, M., Rubin, D., Runge, K., Scalzo, R., Smadja, G., Tao, C., Thomas, R. C., Weaver, B. A., and Wu, C.,"Type Ia Supernova Distance Modulus Bias and Dispersion from K-correction Errors: A Direct Measurement Using Light Curve Fits to Observed Spectral Time Series",The Astrophysical Journal,2015,800:57,doi: 10.1088/0004-637X/800/1/57

We estimate systematic errors due to K-corrections in standard photometric analyses of high-redshift Type Ia supernovae. Errors due to K-correction occur when the spectral template model underlying the light curve fitter poorly represents the actual supernova spectral energy distribution, meaning that the distance modulus cannot be recovered accurately. In order to quantify this effect, synthetic photometry is performed on artificially redshifted spectrophotometric data from 119 low-redshift supernovae from the Nearby Supernova Factory, and the resulting light curves are fit with a conventional light curve fitter. We measure the variation in the standardized magnitude that would be fit for a given supernova if located at a range of redshifts and observed with various filter sets corresponding to current and future supernova surveys. We find significant variation in the measurements of the same supernovae placed at different redshifts regardless of filters used, which causes dispersion greater than ~0.05 mag for measurements of photometry using the Sloan-like filters and a bias that corresponds to a 0.03 shift in w when applied to an outside data set. To test the result of a shift in supernova population or environment at higher redshifts, we repeat our calculations with the addition of a reweighting of the supernovae as a function of redshift and find that this strongly affects the results and would have repercussions for cosmology. We discuss possible methods to reduce the contribution of the K-correction bias and uncertainty.

G. K. Lockwood, S. H. Garofalini,"Proton dynamics at the water-silica interface via dissociative molecular dynamics",Journal of Physical Chemistry C,December 26, 2014,118:29750-2975,doi: 10.1021/jp507640y

A robust and accurate dissociative potential that reproduces the structural and dynamic properties of bulk and nanoconfined water, and proton transport similar to ab initio calculations in bulk water, is used for reactive molecular dynamics simulations of the proton dynamics at the silica/water interface. The simulations are used to evaluate the lifetimes of protonated sites at the interfaces of water with planar amorphous silica surfaces and cylindrical pores in amorphous silica with different densities of water confined in the pores. In addition to lifetimes, the donor/acceptor sites are evaluated and discussed in terms of local atomistic structure. The results of the lifetimes of the protonated sites, including H3O+, SiOH, SiOH2+, and Si–(OH+)–Si sites, are considered. The lifetime of the hydronium ion, H3O+, is considerably shorter near the interface than in bulk water, as are the lifetimes of the other protonated sites. The results indicate the beneficial effect of the amorphous silica surface in enhancing proton transport in wet silica as seen in electrochemical studies and provide the specific molecular mechanisms.

Friesen, B., Baron, E., Wisniewski, J. P., Parrent, J. T., Thomas, R. C., Miller, Timothy R., and Marion, G. H.,"Near-infrared Line Identification in Type Ia Supernovae during the Transitional Phase",The Astrophysical Journal,2014,792:120,doi: 10.1088/0004-637X/792/2/120

We present near-infrared synthetic spectra of a delayed-detonation hydrodynamical model and compare them to observed spectra of four normal Type Ia supernovae ranging from day +56.5 to day +85. This is the epoch during which supernovae are believed to be undergoing the transition from the photospheric phase, where spectra are characterized by line scattering above an optically thick photosphere, to the nebular phase, where spectra consist of optically thin emission from forbidden lines. We find that most spectral features in the near-infrared can be accounted for by permitted lines of Fe II and Co II. In addition, we find that [Ni II] fits the emission feature near 1.98 μm, suggesting that a substantial mass of 58Ni exists near the center of the ejecta in these objects, arising from nuclear burning at high density.

Wen-Ting Tsai, Ahmed Hassan, Purbasha Sarkar, Joaquin Correa, Zoltan Metlagel, Danielle M. Jorgens, Manfred Auer,"From Voxels to Knowledge: A Practical Guide to the Segmentation of Complex Electron Microscopy 3D-Data",August 13, 2014,doi: 10.3791/51673

The bottleneck for cellular 3D electron microscopy is feature extraction (segmentation) in highly complex 3D density maps. We have developed a set of criteria, which provides guidance regarding which segmentation approach (manual, semi-automated, or automated) is best suited for different data types, thus providing a starting point for effective segmentation.

Daya Bay Collaboration: F.P. An, A.B. Balantekin, H.R. Band, W. Beriguete, et. al,"Search for a Light Sterile Neutrino at Daya Bay",Phys. Rev. Letter,July 27, 2014,

A search for light sterile neutrino mixing was performed with the first 217 days of data from the Daya Bay Reactor Antineutrino Experiment. The experiment's unique configuration of multiple baselines from six 2.9~GWth nuclear reactors to six antineutrino detectors deployed in two near (effective baselines 512~m and 561~m) and one far (1579~m) underground experimental halls makes it possible to test for oscillations to a fourth (sterile) neutrino in the 10−3 eV2<|Δm241|<0.3 eV2 range. The relative spectral distortion due to electron antineutrino disappearance was found to be consistent with that of the three-flavor oscillation model. The derived limits on sin22θ14 cover the 10−3 eV2≲|Δm241|≲0.1 eV2 region, which was largely unexplored

Daya Bay Collaboration: F.P. An, A.B. Balantekin, H.R. Band, W. Beriguete, et. al,"Independent Measurement of Theta13 via Neutron Capture on Hydrogen at Daya Bay",Phys. Rev. Letter,June 25, 2014,

A new measurement of the θ13 mixing angle has been obtained at the Daya Bay Reactor Neutrino Experiment via the detection of inverse beta decays tagged by neutron capture on hydrogen. The antineutrino events for hydrogen capture are distinct from those for gadolinium capture with largely different systematic uncertainties, allowing a determination independent of the gadolinium-capture result and an improvement on the precision of θ13 measurement. With a 217-day antineutrino data set obtained with six antineutrino detectors and from six 2.9 GWth reactors, the rate deficit observed at the far hall is interpreted as sin22θ13=0.083±0.018 in the three-flavor oscillation model. When combined with the gadolinium-capture result from Daya Bay, we obtain sin22θ13=0.089±0.008 as the final result for the six-antineutrino-detector configuration of the Daya Bay experiment.

M. Kagan, G. K. Lockwood, S. H. Garofalini,"Reactive simulations of the activation barrier to dissolution of amorphous silica in water",Physical Chemistry Chemical Physics,May 28, 2014,16:9294-9301,doi: 10.1039/c4cp00030g

Molecular dynamics simulations employing reactive potentials were used to determine the activation barriers to the dissolution of the amorphous SiO2 surface in the presence of a 2 nm overlayer of water. The potential of mean force calculations of the reactions of water molecules with 15 different starting Q4 sites (Qi is the Si site with i bridging oxygen neighbors) to eventually form the dissolved Q0 site were used to obtain the barriers. Activation barriers for each step in the dissolution process, from the Q4 to Q3 to Q2 to Q1 to Q0 were obtained. Relaxation runs between each reaction step enabled redistribution of the water above the surface in response to the new Qi site configuration. The rate-limiting step observed in the simulations was in both the Q32 reaction (a Q3 site changing to a Q2 site) and the Q21 reaction, each with an average barrier of ∼14.1 kcal mol(-1). However, the barrier for the overall reaction from the Q4 site to a Q0 site, averaged over the maximum barrier for each of the 15 samples, was 15.1 kcal mol(-1). This result is within the lower end of the experimental data, which varies from 14-24 kcal mol(-1), while ab initio calculations using small cluster models obtain values that vary from 18-39 kcal mol(-1). Constraints between the oxygen bridges from the Si site and the connecting silica structure, the presence of pre-reaction strained siloxane bonds, and the location of the reacting Si site within slight concave surface contours all affected the overall activation barriers.

"Type Ia supernova bolometric light curves and ejected mass estimates from the Nearby Supernova Factory",Monthly Notices of the Royal Astronomical Society,2014,440:1498,doi: 10.1093/mnras/stu350

We present a sample of normal Type Ia supernovae (SNe Ia) from the Nearby Supernova Factory data set with spectrophotometry at sufficiently late phases to estimate the ejected mass using the bolometric light curve. We measure 56Ni masses from the peak bolometric luminosity, then compare the luminosity in the 56Co-decay tail to the expected rate of radioactive energy release from ejecta of a given mass. We infer the ejected mass in a Bayesian context using a semi-analytic model of the ejecta, incorporating constraints from contemporary numerical models as priors on the density structure and distribution of 56Ni throughout the ejecta. We find a strong correlation between ejected mass and light-curve decline rate, and consequently 56Ni mass, with ejected masses in our data ranging from 0.9 to 1.4 M. Most fast-declining (SALT2 x1 < -1) normal SNe Ia have significantly sub-Chandrasekhar ejected masses in our fiducial analysis.

McCully, C., Jha, S. W., Foley, R. J., Chornock, R., Holtzman, J. A., Balam, D. D., Branch, D., Filippenko, A. V., Frieman, J., Fynbo, J., Galbany, L., Ganeshalingam, M., Garnavich, P. M., Graham, M. L., Hsiao, E. Y., Leloudas, G., Leonard, D. C., Li, W., Riess, A. G., Sako, M., Schneider, D. P., Silverman, J. M., Sollerman, J., Steele, T. N., Thomas, R. C., Wheeler, J. C., and Zheng, C.,"Hubble Space Telescope and Ground-based Observations of the Type Iax Supernovae SN 2005hk and SN 2008A",The Astrophysical Journal,2014,786:134,doi: 10.1088/0004-637X/786/2/134

We present Hubble Space Telescope (HST) and ground-based optical and near-infrared observations of SN 2005hk and SN 2008A, typical members of the Type Iax class of supernovae (SNe). Here we focus on late-time observations, where these objects deviate most dramatically from all other SN types. Instead of the dominant nebular emission lines that are observed in other SNe at late phases, spectra of SNe 2005hk and 2008A show lines of Fe II, Ca II, and Fe I more than a year past maximum light, along with narrow [Fe II] and [Ca II] emission. We use spectral features to constrain the temperature and density of the ejecta, and find high densities at late times, with ne >~ 109 cm-3. Such high densities should yield enhanced cooling of the ejecta, making these objects good candidates to observe the expected "infrared catastrophe," a generic feature of SN Ia models. However, our HST photometry of SN 2008A does not match the predictions of an infrared catastrophe. Moreover, our HST observations rule out a "complete deflagration" that fully disrupts the white dwarf for these peculiar SNe, showing no evidence for unburned material at late times. Deflagration explosion models that leave behind a bound remnant can match some of the observed properties of SNe Iax, but no published model is consistent with all of our observations of SNe 2005hk and 2008A.

Parrent, J. T., Friesen, B., Parthasarathy, M.,"A Review of Type Ia Supernova Spectra",Astrophysics and Space Science,2014,351:1-52,doi: 10.1007/s10509-014-1830-1

SN 2011fe was the nearest and best-observed type Ia supernova in a generation, and brought previous incomplete datasets into sharp contrast with the detailed new data. In retrospect, documenting spectroscopic behaviors of type Ia supernovae has been more often limited by sparse and incomplete temporal sampling than by consequences of signal-to-noise ratios, telluric features, or small sample sizes. As a result, type Ia supernovae have been primarily studied insofar as parameters discretized by relative epochs and incomplete temporal snapshots near maximum light. Here we discuss a necessary next step toward consistently modeling and directly measuring spectroscopic observables of type Ia supernova spectra. In addition, we analyze current spectroscopic data in the parameter space defined by empirical metrics, which will be relevant even after progenitors are observed and detailed models are refined.

Daya Bay Collaboration: F.P. An, A.B. Balantekin, H.R. Band, W. Beriguete, et. al,"Spectral measurement of electron antineutrino oscillation amplitude and frequency at Daya Bay",Phys. Rev. Letter,October 24, 2013,

A measurement of the energy dependence of antineutrino disappearance at the Daya Bay Reactor Neutrino Experiment is reported. Electron antineutrinos from six GW reactors were detected with six detectors deployed in two near (effective baselines 512 m and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41589 (203809 and 92912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude and the first direct measurement of the mass-squared difference is obtained using the observed rates and energy spectra in a three-neutrino framework.

This value obtained is consistent with measured by muon neutrino disappearance, supporting the three-flavor oscillation model.

Full Author List:

F.P. An, A.B. Balantekin, H.R. Band, W. Beriguete, M. Bishai, S. Blyth, R.L. Brown, I. Butorov, G.F. Cao, J. Cao, R. Carr, Y.L. Chan, J.F. Chang, Y. Chang, C. Chasman, H.S. Chen, H.Y. Chen, S.J. Chen, S.M. Chen, X.C. Chen, X.H. Chen, Y. Chen, Y.X. Chen, Y.P. Cheng, J.J. Cherwinka, M.C. Chu, J.P. Cummings, J. de Arcos, Z.Y. Deng, Y.Y. Ding, M. Diwan, E. Draeger, X.F. Du, D.A. Dwyer, W.R. Edwards, S.R. Ely, J.Y. Fu, L.Q. Ge, R. Gill, M. Gonchar, G.H. Gong, H. Gong, Y.A. Gornushkin, W.Q. Gu, M.Y. Guan, X.H. Guo, R.W. Hackenburg, R.L. Hahn, G.H. Han, S. Hans,M. He, K.M. Heeger, Y.K. Heng, P. Hinrichs, J. Hor, Y.B. Hsiung, B.Z. Hu, L.J. Hu, L.M. Hu, T. Hu, W. Hu, E.C. Huang, H.X. Huang, H.Z. Huang, X.T. Huang, P. Huber, G. Hussain, Z. Isvan, D.E. Jaffe, P. Jaffke, S. Jetter, X.L. Ji, X.P. Ji, H.J. Jiang, J.B. Jiao, R.A. Johnson, L. Kang, S.H. Kettell, M. Kramer, K.K. Kwan, M.W. Kwok, T. Kwok, W.C. Lai, W.H. Lai, K. Lau, L. Lebanowski, J. Lee, R.T. Lei, R. Leitner,A. Leung, J.K.C. Leung, C.A. Lewis, D.J. Li, F. Li, G.S. Li, Q.J. Li, W.D. Li, X.N. Li, X.Q. Li, Y.F. Li, Z.B. Li, H. Liang, C.J. Lin, G.L. Lin, S.K. Lin, Y.C. Lin, J.J. Ling, J.M. Link, L. Littenberg, B. Littlejohn,D.W. Liu, H. Liu, J.C. Liu, J.L. Liu, S.S. Liu, Y.B. Liu, C. Lu, H.Q. Lu, K.B. Luk, Q.M. Ma, X.B. Ma, X.Y. Ma, Y.Q. Ma, K.T. McDonald, M.C. McFarlane, R.D. McKeown, Y. Meng, I. Mitchell, Y. Nakajima, J. Napolitano, D. Naumov, E. Naumova, I. Nemchenok, H.Y. Ngai, W.K. Ngai, Z. Ning, J.P. Ochoa-Ricoux, A. Olshevski, S. Patton, V. Pec, J.C. Peng, L.E. Piilonen, L. Pinsky, C.S.J. Pun, F.Z. Qi, M. Qi, X. Qian, N. Raper, B. Ren, J. Ren, R. Rosero, B. Roskovec, X.C. Ruan, B.B. Shao, H. Steiner, G.X. Sun, J.L. Sun, Y.H. Tam, H.K. Tanaka, X. Tang, H. Themann, S. Trentalange, O. Tsai, K.V. Tsang, R.H.M. Tsang, C.E. Tull, Y.C. Tung, B. Viren, V. Vorobel, C.H. Wang, L.S. Wang, L.Y. Wang, L.Z. Wang, M. Wang, N.Y. Wang, R.G. Wang, W. Wang, W.W. Wang, Y.F. Wang, Z. Wang, Z. Wang, Z.M. Wang, D.M. Webber, H.Y. Wei, Y.D. Wei, L.J. Wen, K. Whisnant, C.G. White, L. Whitehead, T.S. Wise, H.L.H. Wong, S.C.F. Wong, E. Worcester, Q. Wu, D.M. Xia, J.K. Xia, X. Xia, Z.Z. Xing, J. Xu, J.L. Xu, J.Y. Xu, Y. Xu, T. Xue, J. Yan, C.G. Yang, L. Yang, M.S. Yang, M. Ye, M.F. Yeh, Y.S. Yeh, B.L. Young, G.Y. Yu, J.Y. Yu, Z.Y. Yu, S.L. Zang, L. Zhan, C. Zhang, F.H. Zhang, J.W. Zhang, Q.M. Zhang, S.H. Zhang, Y.C. Zhang, Y.H. Zhang, Y.M. Zhang, Y.X. Zhang, Z.J. Zhang, Z.P. Zhang, Z.Y. Zhang, J. Zhao, Q.W. Zhao, Y.B. Zhao, L. Zheng, W.L. Zhong, L. Zhou, Z.Y. Zhou, H.L. Zhuang, J.H. Zou

D.C. Eder, A.C. Fisher, A.E. Koniges and N.D. Masters,"Modelling debris and shrapnel generation in inertial confinement fusion experiments",Nuclear Fusion 53 113037,2013,doi: 10.1088/0029-5515/53/11/113037

Modelling and mitigation of damage are crucial for safe and economical operation of high-power laser facilities. Experiments at the National Ignition Facility use a variety of targets with a range of laser energies spanning more than two orders of magnitude (~14 kJ to ~1.9 MJ). Low-energy inertial confinement fusion experiments are used to study early-time x-ray load symmetry on the capsule, shock timing, and other physics issues. For these experiments, a significant portion of the target is not completely vaporized and late-time (hundreds of ns) simulations are required to study the generation of debris and shrapnel from these targets. Damage to optics and diagnostics from shrapnel is a major concern for low-energy experiments. We provide the first full-target simulations of entire cryogenic targets, including the Al thermal mechanical package and Si cooling rings. We use a 3D multi-physics multi-material hydrodynamics code, ALE-AMR, for these late-time simulations. The mass, velocity, and spatial distribution of shrapnel are calculated for three experiments with laser energies ranging from 14 to 250 kJ. We calculate damage risk to optics and diagnostics for these three experiments. For the lowest energy re-emit experiment, we provide a detailed analysis of the effects of shrapnel impacts on optics and diagnostics and compare with observations of damage sites.

S. Hachinger, P. A. Mazzali, M. Sullivan, R. S., K. Maguire, A. Gal-Yam, D. A. Howell, P. E., E. Baron, J. Cooke, I. Arcavi, D., B. Dilday, P. A. James, M. M. Kasliwal, S. R., E. O. Ofek, R. R. Laher, J. Parrent, J. Surace, O. Yaron, E. S. Walker,"The UV/optical spectra of the Type Ia supernova SN 2010jn: a bright supernova with outer layers rich in iron-group elements",Monthly Notices of the RAS,2013,429:2228-2248,doi: 10.1093/mnras/sts492

Radiative transfer studies of Type Ia supernovae (SNe Ia) hold the promise of constraining both the density profile of the SN ejecta and its stratification by element abundance which, in turn, may discriminate between different explosion mechanisms and progenitor classes. Here we analyse the Type Ia SN 2010jn (PTF10ygu) in detail, presenting and evaluating near-ultraviolet (near-UV) spectra from the Hubble Space Telescope and ground-based optical spectra and light curves. SN 2010jn was discovered by the Palomar Transient Factory (PTF) 15 d before maximum light, allowing us to secure a time series of four near-UV spectra at epochs from -10.5 to +4.8 d relative to B-band maximum. The photospheric near-UV spectra are excellent diagnostics of the iron-group abundances in the outer layers of the ejecta, particularly those at very early times. Using the method of Abundance Tomography' we derive iron-group abundances in SN 2010jn with a precision better than in any previously studied SN Ia. Optimum fits to the data can be obtained if burned material is present even at high velocities, including significant mass fractions of iron-group elements. This is consistent with the slow decline rate (or high stretch') of the light curve of SN 2010jn, and consistent with the results of delayed-detonation models. Early-phase UV spectra and detailed time-dependent series of further SNe Ia offer a promising probe of the nature of the SN Ia mechanism.

Friesen, B., Baron, E., Branch, D., Chen, B., Parrent, J., Thomas, R. C.,"Supernova Resonance-scattering Line Profiles in the Absence of a Photosphere",The Astrophysical Journal Supplements Series,2012,203:1,doi: 10.1088/0067-0049/203/1/12

In supernova (SN) spectroscopy relatively little attention has been given to the properties of optically thick spectral lines in epochs following the photosphere's recession. Most treatments and analyses of post-photospheric optical spectra of SNe assume that forbidden-line emission comprises most if not all spectral features. However, evidence exists that suggests that some spectra exhibit line profiles formed via optically thick resonance-scattering even months or years after the SN explosion. To explore this possibility, we present a geometrical approach to SN spectrum formation based on the "Elementary Supernova" model, wherein we investigate the characteristics of resonance-scattering in optically thick lines while replacing the photosphere with a transparent central core emitting non-blackbody continuum radiation, akin to the optical continuum provided by decaying 56Co formed during the explosion. We develop the mathematical framework necessary for solving the radiative transfer equation under these conditions and calculate spectra for both isolated and blended lines. Our comparisons with analogous results from the Elementary Supernova code SYNOW reveal several marked differences in line formation. Most notably, resonance lines in these conditions form P Cygni-like profiles, but the emission peaks and absorption troughs shift redward and blueward, respectively, from the line's rest wavelength by a significant amount, despite the spherically symmetric distribution of the line optical depth in the ejecta. These properties and others that we find in this work could lead to misidentification of lines or misattribution of properties of line-forming material at post-photospheric times in SN optical spectra.

Daya Bay Collaboration, F. P. An, Q. An, J. Z. Bai et al.,"Improved Measurement of Electron Antineutrino Disappearance at Daya Bay",Phys. Rev. Letter,October 23, 2012,doi: 10/2012; DOI:10.1088/1674-1137/37/1/011001

ABSTRACT: We report an improved measurement of the neutrino mixing angle $\theta_{13}$ from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for $\sin^22\theta_{13}$ with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GW$_{\rm th}$ were detected in six antineutrino detectors deployed in two near (flux-weighted baselines of 470 m and 576 m) and one far (1648 m) underground experimental halls. Using 139 days of data, 28909 (205308) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is $0.944\pm 0.007({\rm stat.}) \pm 0.003({\rm syst.})$. An analysis of the relative rates in six detectors finds $\sin^22\theta_{13}=0.089\pm 0.010({\rm stat.})\pm0.005({\rm syst.})$ in a three-neutrino framework.

Full Author List:

Parrent, J. T., Howell, D. A., Friesen, B., Thomas, R. C., Fesen, R. A., Milisavljevic, D., Bianco, F. B., Dilday, B., Nugent, P., Baron, E., Arcavi, I., Ben-Ami, S., Bersier, D., Bildsten, L., Bloom, J., Cao, Y., Cenko, S. B., Filippenko, A. V., Gal-Yam, A., Kasliwal, M. M., Konidaris, N., Kulkarni, S. R., Law, N. M., Levitan, D., Maguire, K., Mazzali, P. A., Ofek, E. O., Pan, Y., Polishook, D., Poznanski, D., Quimby, R. M., Silverman, J. M., Sternberg, A., Sullivan, M., Walker, E. S., Xu, Dong, Buton, C., Pereira, R.,"Analysis of the Early-time Optical Spectra of SN 2011fe in M101",The Astrophysical Journal Letters,2012,752, doi: 10.1088/2041-8205/752/2/L26

The nearby Type Ia supernova (SN Ia) SN 2011fe in M101 (cz = 241 km s–1) provides a unique opportunity to study the early evolution of a "normal" SN Ia, its compositional structure, and its elusive progenitor system. We present 18 high signal-to-noise spectra of SN 2011fe during its first month beginning 1.2 days post-explosion and with an average cadence of 1.8 days. This gives a clear picture of how various line-forming species are distributed within the outer layers of the ejecta, including that of unburned material (C+O). We follow the evolution of C II absorption features until they diminish near maximum light, showing overlapping regions of burned and unburned material between ejection velocities of 10,000 and 16,000 km s–1. This supports the notion that incomplete burning, in addition to progenitor scenarios, is a relevant source of spectroscopic diversity among SNe Ia. The observed evolution of the highly Doppler-shifted O I λ7774 absorption features detected within 5 days post-explosion indicates the presence of O I with expansion velocities from 11,500 to 21,000 km s–1. The fact that some O I is present above C II suggests that SN 2011fe may have had an appreciable amount of unburned oxygen within the outer layers of the ejecta.

F. P. An, J. Z. Bai, A. B. Balantekin, et al.,"Observation of electron-antineutrino disappearance at Daya Bay",Phys. Rev. Letter,March 8, 2012,

The Daya Bay Reactor Neutrino Experiment has measured a non-zero value for the neutrino mixing angle θ13 with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GWth reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With 55 days of data, 10416 (80376) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is  R=0.940 ±0.011( stat) ± 0.004( syst). A rate-only analysis finds sin2 2 θ13 - 0.092 ± 0.016( stat}) ± 0.005(syst) in a three-neutrino framework.

Full Author list: F. P. An, J. Z. Bai, A. B. Balantekin, H. R. Band, D. Beavis, W. Beriguete, M. Bishai, S. Blyth, R. L. Brown, G. F. Cao, J. Cao, R. Carr, W. T. Chan, J. F. Chang, Y. Chang, C. Chasman, H. S. Chen, H. Y. Chen, S. J. Chen, S. M. Chen, X. C. Chen, X. H. Chen, X. S. Chen, Y. Chen, Y. X. Chen, J. J. Cherwinka, M. C. Chu, J. P. Cummings, Z. Y. Deng, Y. Y. Ding, M. V. Diwan, L. Dong, E. Draeger, X. F. Du, D. A. Dwyer, W. R. Edwards, S. R. Ely, S. D. Fang, J. Y. Fu, Z. W. Fu, L. Q. Ge, V. Ghazikhanian, R. L. Gill, J. Goett, M. Gonchar, G. H. Gong, H. Gong, Y. A. Gornushkin, L. S. Greenler, W. Q. Gu, M. Y. Guan, X. H. Guo, R. W. Hackenburg, R. L. Hahn, S. Hans, M. He, Q. He, W. S. He, K. M. Heeger, Y. K. Heng, P. Hinrichs, T. H. Ho, Y. K. Hor, Y. B. Hsiung, B. Z. Hu, T. Hu, T. Hu, H. X. Huang, H. Z. Huang, P. W. Huang, X. Huang, X. T. Huang, P. Huber, Z. Isvan, D. E. Jaffe, S. Jetter, X. L. Ji, X. P. Ji, H. J. Jiang, W. Q. Jiang, J. B. Jiao, R. A. Johnson, L. Kang, S. H. Kettell, M. Kramer, K. K. Kwan, M. W. Kwok, T. Kwok, C. Y. Lai, W. C. Lai, W. H. Lai, K. Lau, L. Lebanowski, J. Lee, M. K. P. Lee, R. Leitner, J. K. C. Leung, K. Y. Leung, C. A. Lewis, B. Li, F. Li, G. S. Li, J. Li, Q. J. Li, S. F. Li, W. D. Li, X. B. Li, X. N. Li, X. Q. Li, Y. Li, Z. B. Li, H. Liang, J. Liang, C. J. Lin, G. L. Lin, S. K. Lin, S. X. Lin, Y. C. Lin, J. J. Ling, J. M. Link, L. Littenberg, B. R. Littlejohn, B. J. Liu, C. Liu, D. W. Liu, H. Liu, J. C. Liu, J. L. Liu, S. Liu, X. Liu, Y. B. Liu, C. Lu, H. Q. Lu, A. Luk, K. B. Luk, T. Luo, X. L. Luo, L. H. Ma, Q. M. Ma, X. B. Ma, X. Y. Ma, Y. Q. Ma, B. Mayes, K. T. McDonald, M. C. McFarlane, R. D. McKeown, Y. Meng, D. Mohapatra, J. E. Morgan, Y. Nakajima, J. Napolitano, D. Naumov, I. Nemchenok, C. Newsom, H. Y. Ngai, W. K. Ngai, Y. B. Nie, Z. Ning, J. P. Ochoa-Ricoux, A. Olshevski, A. Pagac, S. Patton, C. Pearson, V. Pec, J. C. Peng, L. E. Piilonen, L. Pinsky, C. S. J. Pun, F. Z. Qi, M. Qi, X. Qian, N. Raper, R. Rosero, B. Roskovec, X. C. Ruan, B. Seilhan, B. B. Shao, K. Shih, H. Steiner, P. Stoler, G. X. Sun, J. L. Sun, Y. H. Tam, H. K. Tanaka, X. Tang, H. Themann, Y. Torun, S. Trentalange, O. Tsai, K. V. Tsang, R. H. M. Tsang, C. Tull, B. Viren, S. Virostek, V. Vorobel, C. H. Wang, L. S. Wang, L. Y. Wang, L. Z. Wang, M. Wang, N. Y. Wang, R. G. Wang, T. Wang, W. Wang, X. Wang, X. Wang, Y. F. Wang, Z.Wang, Z.Wang, Z. M.Wang, D. M.Webber, Y. D.Wei, L. J.Wen, D. L.Wenman, K. Whisnant, C. G. White, L. Whitehead, C. A. Whitten Jr., J. Wilhelmi, T. Wise, H. C. Wong, H. L. H. Wong, J. Wong, E. T. Worcester, F. F. Wu, Q. Wu, D. M. Xia, S. T. Xiang, Q. Xiao, Z. Z. Xing, G. Xu, J. Xu, J. Xu, J. L. Xu, W. Xu, Y. Xu, T. Xue, C. G. Yang, L. Yang, M. Ye, M. Yeh, Y. S. Yeh, K. Yip, B. L. Young, Z. Y. Yu, L. Zhan, C. Zhang, F. H. Zhang, J. W. Zhang, Q. M. Zhang, K. Zhang, Q. X. Zhang, S. H. Zhang, Y. C. Zhang, Y. H. Zhang, Y. X. Zhang, Z. J. Zhang, Z. P. Zhang, Z. Y. Zhang, J. Zhao, Q. W. Zhao, Y. B. Zhao, L. Zheng, W. L. Zhong, L. Zhou, Z. Y. Zhou, H. L. Zhuang, J. H. Zou

Joshua S. Bloom, Daniel Kasen, Ken J. Shen, Peter E. Nugent, Nathaniel R. Butler, Melissa L. Graham, D. Andrew Howell, Ulrich Kolb, Stefan Holmes, Carole A. Haswell, Vadim Burwitz, Juan Rodriguez, and Mark Sullivan,"SN 2010jp (PTF10aaxi): a jet in a Type II supernova",Monthly Notices of the Royal Astronomical Society,February 2012,2181,

We present photometry and spectroscopy of the peculiar Type II supernova (SN) SN 2010jp, also named PTF10aaxi. The light curve exhibits a linear decline with a relatively low peak absolute magnitude of only −15.9 (unfiltered), and a low radioactive decay luminosity at late times, which suggests a low synthesized nickel mass of M (56 Ni) ≲ 0.003  M. Spectra of SN 2010jp display an unprecedented triple-peaked Hα line profile, showing (1) a narrow (full width at half-maximum >rsim800 km s−1) central component that suggests shock interaction with dense circumstellar material (CSM); (2) high-velocity blue and red emission features centred at −12 600 and +15 400 km s−1, respectively; and (3) very broad wings extending from −22 000 to +25 000 km s−1. These features persist over multiple epochs during the ∼100 d after explosion. We propose that this line profile indicates a bipolar jet-driven explosion, with the central component produced by normal SN ejecta and CSM interaction at mid and low latitudes, while the high-velocity bumps and broad-line wings arise in a non-relativistic bipolar jet. Two variations of the jet interpretation seem plausible: (1) a fast jet mixes 56Ni to high velocities in polar zones of the H-rich envelope; or (2) the reverse shock in the jet produces blue and red bumps in Balmer lines when a jet interacts with dense CSM. Jet-driven Type II SNe are predicted for collapsars resulting from a wide range of initial masses above 25 M, especially at subsolar metallicity. This seems consistent with the SN host environment, which is either an extremely low-luminosity dwarf galaxy or the very remote parts of an interacting pair of star-forming galaxies. It also seems consistent with the apparently low 56Ni mass that may accompany black hole formation. We speculate that the jet survives to produce observable signatures because the star’s H envelope was very low mass, having been mostly stripped away by the previous eruptive mass-loss indicated by the Type IIn features in the spectrum. http://dx.doi.org/10.1111/j.1365-2966.2011.20104.x

Joshua S. Bloom, Daniel Kasen, Ken J. Shen, Peter E. Nugent, Nathaniel R. Butler, Melissa L. Graham, D. Andrew Howell, Ulrich Kolb, Stefan Holmes, Carole A. Haswell, Vadim Burwitz, Juan Rodriguez, and Mark Sullivan,"A Compact Degenerate Primary-star Progenitor of SN 2011fe",Astrophysical Journal,January 2012,744:L17,

While a white dwarf (WD) is, from a theoretical perspective, the most plausible primary star of a Type Ia supernova (SN Ia), many other candidates have not been formally ruled out. Shock energy deposited in the envelope of any exploding primary contributes to the early SN brightness and, since this radiation energy is degraded by expansion after the explosion, the diffusive luminosity depends on the initial primary radius. We present a new non-detection limit of the nearby SN Ia 2011fe, obtained at a time that appears to be just 4 hr after explosion, allowing us to directly constrain the initial primary radius (Rp ). Coupled with the non-detection of a quiescent X-ray counterpart and the inferred synthesized 56Ni mass, we show that Rp 0.02 R  (a factor of five smaller than previously inferred), that the average density of the primary must be ρ p > 104 g cm–3, and that the effective temperature must be less than a few × 105 K. This rules out hydrogen-burning main-sequence stars and giants. Constructing the helium-burning and carbon-burning main sequences, we find that such objects are also excluded. By process of elimination, we find that only degeneracy-supported compact objects—WDs and neutron stars—are viable as the primary star of SN 2011fe. With few caveats, we also restrict the companion (secondary) star radius to R c  0.1 R , excluding Roche-lobe overflowing red giant and main-sequence companions to high significance.

http://dx.doi.org/10.1088/2041-8205/744/2/L17

Thomas, R. C.; Aldering, G.; Antilogus, P.; Aragon, C.; Bailey, S.; Baltay, C.; Bongard, S.; Buton, C.; Canto, A.; Childress, M.; Chotard, N.; Copin, Y.; Fakhouri, H. K.; Gangler, E.; Hsiao, E. Y.; Kerschhaggl, M.; Kowalski, M.; Loken, S.; Nugent, P.; Paech, K.; Pain, R.; Pecontal, E.; Pereira, R.; Perlmutter, S.; Rabinowitz, D.; Rigault, M.; Rubin, D.; Runge, K.; Scalzo, R.; Smadja, G.; Tao, C.; Weaver, B. A.; Wu, C.; (The Nearby Supernova Factory); Brown, P. J.; Milne, P. A.,"Type Ia Supernova Carbon Footprints",Astrophysical Journal,December 2011,743:27,

We present convincing evidence of unburned carbon at photospheric velocities in new observations of five Type Ia supernovae (SNe Ia) obtained by the Nearby Supernova Factory. These SNe are identified by examining 346 spectra from 124 SNe obtained before +2.5 days relative to maximum. Detections are based on the presence of relatively strong C II λ6580 absorption "notches" in multiple spectra of each SN, aided by automated fitting with the SYNAPPS code. Four of the five SNe in question are otherwise spectroscopically unremarkable, with ions and ejection velocities typical of SNe Ia, but spectra of the fifth exhibit high-velocity (v > 20, 000 km s–1) Si II and Ca II features. On the other hand, the light curve properties are preferentially grouped, strongly suggesting a connection between carbon-positivity and broadband light curve/color behavior: three of the five have relatively narrow light curves but also blue colors and a fourth may be a dust-reddened member of this family. Accounting for signal to noise and phase, we estimate that 22+10 – 6% of SNe Ia exhibit spectroscopic C II signatures as late as –5 days with respect to maximum. We place these new objects in the context of previously recognized carbon-positive SNe Ia and consider reasonable scenarios seeking to explain a physical connection between light curve properties and the presence of photospheric carbon. We also examine the detailed evolution of the detected carbon signatures and the surrounding wavelength regions to shed light on the distribution of carbon in the ejecta. Our ability to reconstruct the C II λ6580 feature in detail under the assumption of purely spherical symmetry casts doubt on a "carbon blobs" hypothesis, but does not rule out all asymmetric models. A low volume filling factor for carbon, combined with line-of-sight effects, seems unlikely to explain the scarcity of detected carbon in SNe Ia by itself. http://dx.doi.org/10.1088/0004-637X/743/1/27

Li, Weidong; Bloom, Joshua S.; Podsiadlowski, Philipp; Miller, Adam A.; Cenko, S. Bradley; Jha, Saurabh W.; Sullivan, Mark; Howell, D. Andrew; Nugent, Peter E.; Butler, Nathaniel R.; Ofek, Eran O.; Kasliwal, Mansi M.; Richards, Joseph W.; Stockton, Alan; Shih, Hsin-Yi; Bildsten, Lars; Shara, Michael M.; Bibby, Joanne; Filippenko, Alexei V.; Ganeshalingam, Mohan; Silverman, Jeffrey M.; Kulkarni, S. R.; Law, Nicholas M.; Poznanski, Dovi; Quimby, Robert M.; McCully, Curtis; Patel, Brandon; Maguire, Kate; Shen, Ken J.,"Exclusion of a luminous red giant as a companion star to the progenitor of supernova SN 2011fe",Nature,December 2011,480:348-350,

Type Ia supernovae are thought to result from a thermonuclear explosion of an accreting white dwarf in a binary system1, 2, but little is known of the precise nature of the companion star and the physical properties of the progenitor system. There are two classes of models1, 3: double-degenerate (involving two white dwarfs in a close binary system2, 4) and single-degenerate models5, 6. In the latter, the primary white dwarf accretes material from a secondary companion until conditions are such that carbon ignites, at a mass of 1.38 times the mass of the Sun. The type Ia supernova SN 2011fe was recently detected in a nearby galaxy7. Here we report an analysis of archival images of the location of SN 2011fe. The luminosity of the progenitor system (especially the companion star) is 10–100 times fainter than previous limits on other type Ia supernova progenitor systems8, 9, 10, allowing us to rule out luminous red giants and almost all helium stars as the mass-donating companion to the exploding white dwarf.

Nugent, Peter E.; Sullivan, Mark; Cenko, S. Bradley; Thomas, Rollin C.; Kasen, Daniel; Howell, D. Andrew; Bersier, David; Bloom, Joshua S.; Kulkarni, S. R.; Kandrashoff, Michael T.; Filippenko, Alexei V.; Silverman, Jeffrey M.; Marcy, Geoffrey W.; Howard, Andrew W.; Isaacson, Howard T.; Maguire, Kate; Suzuki, Nao; Tarlton, James E.; Pan, Yen-Chen; Bildsten, Lars; Fulton, Benjamin J.; Parrent, Jerod T.; Sand, David; Podsiadlowski, Philipp; Bianco, Federica B.; Dilday, Benjamin; Graham, Melissa L.; Lyman, Joe; James, Phil; Kasliwal, Mansi M.; Law, Nicholas M.; Quimby, Robert M.; Hook, Isobel M.; Walker, Emma S.; Mazzali, Paolo; Pian, Elena; Ofek, Eran O.; Gal-Yam, Avishay; Poznanski, Dovi,"Supernova SN 2011fe from an exploding carbon-oxygen white dwarf star",Nature,December 2011,480:344-347,

Type Ia supernovae have been used empirically as `standard candles' to demonstrate the acceleration of the expansion of the Universe even though fundamental details, such as the nature of their progenitor systems and how the stars explode, remain a mystery. There is consensus that a white dwarf star explodes after accreting matter in a binary system, but the secondary body could be anything from a main-sequence star to a red giant, or even another white dwarf. This uncertainty stems from the fact that no recent type Ia supernova has been discovered close enough to Earth to detect the stars before explosion. Here we report early observations of supernova SN 2011fe in the galaxy M101 at a distance from Earth of 6.4 megaparsecs. We find that the exploding star was probably a carbon-oxygen white dwarf, and from the lack of an early shock we conclude that the companion was probably a main-sequence star. Early spectroscopy shows high-velocity oxygen that slows rapidly, on a timescale of hours, and extensive mixing of newly synthesized intermediate-mass elements in the outermost layers of the supernova. A companion paper uses pre-explosion images to rule out luminous red giants and most helium stars as companions to the progenitor. http://dx.doi.org/10.1038/nature10644

Iair Arcavi, Avishay Gal-Yam, Ofer Yaron, Assaf Sternberg, Itay Rabinak, Eli Waxman, Mansi M. Kasliwal, Robert M. Quimby, Eran O. Ofek, Assaf Horesh, Shrinivas R. Kulkarni, Alexei V. Filippenko, Jeffrey M. Silverman, S. Bradley Cenko, Weidong Li, Joshua S. Bloom, Mark Sullivan, Peter E. Nugent, Dovi Poznanski, Evgeny Gorbikov, Benjamin J. Fulton, D. Andrew Howell, David Bersier, Amedee Riou, Stephane Lamotte-Bailey, Thomas Griga, Judith G. Cohen, Stephan Hachinger, David Polishook, Dong Xu, Sagi Ben-Ami, Ilan Manulis, Emma S. Walker, Kate Maguire, Yen-Chen Pan, Thomas Matheson, Paolo A. Mazzali, Elena Pian, Derek B. Fox, Neil Gehrels, Nicholas Law, Philip James, Jonathan M. Marchant, Robert J. Smith, Chris J. Mottram, Robert M. Barnsley, Michael T. Kandrashoff and Kelsey I. Clubb,"SN 2011dh: Discovery of a Type IIb Supernova from a Compact Progenitor in the Nearby Galaxy M51",Astrophysical Journal,December 2011,742:L18,

On 2011 May 31 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We discovered this event using small telescopes equipped with CCD cameras and also detected it with the Palomar Transient Factory survey, rapidly confirming it to be a Type II SN. Here, we present multi-color ultraviolet through infrared photometry which is used to calculate the bolometric luminosity and a series of spectra. Our early-time observations indicate that SN 2011dh resulted from the explosion of a relatively compact progenitor star. Rapid shock-breakout cooling leads to relatively low temperatures in early-time spectra, compared to explosions of red supergiant stars, as well as a rapid early light curve decline. Optical spectra of SN 2011dh are dominated by H lines out to day 10 after explosion, after which He i lines develop. This SN is likely a member of the cIIb (compact IIb) class, with progenitor radius larger than that of SN 2008ax and smaller than the eIIb (extended IIb) SN 1993J progenitor. Our data imply that the object identified in pre-explosion Hubble Space Telescope images at the SN location is possibly a companion to the progenitor or a blended source, and not the progenitor star itself, as its radius (~1013 cm) would be highly inconsistent with constraints from our post-explosion spectra. http://dx.doi.org/10.1088/2041-8205/742/2/L18

Corsi, A.; Ofek, E. O.; Frail, D. A.; Poznanski, D.; Arcavi, I.; Gal-Yam, A.; Kulkarni, S. R.; Hurley, K.; Mazzali, P. A.; Howell, D. A.; Kasliwal, M. M.; Green, Y.; Murray, D.; Sullivan, M.; Xu, D.; Ben-ami, S.; Bloom, J. S.; Cenko, S. B.; Law, N. M.; Nugent, P.; Quimby, R. M.; Pal'shin, V.; Cummings, J.; Connaughton, V.; Yamaoka, K.; Rau, A.; Boynton, W.; Mitrofanov, I.; Goldsten, J.,"PTF 10bzf (SN 2010ah): A Broad-line Ic Supernova Discovered by the Palomar Transient Factory",Astrophysical Journal,November 2011,741:76,

We present the discovery and follow-up observations of a broad-line Type Ic supernova (SN), PTF 10bzf (SN 2010ah), detected by the Palomar Transient Factory (PTF) on 2010 February 23. The SN distance is 218 Mpc, greater than GRB 980425/SN 1998bw and GRB 060218/SN 2006aj, but smaller than the other SNe firmly associated with gamma-ray bursts (GRBs). We conducted a multi-wavelength follow-up campaign with Palomar 48 inch, Palomar 60 inch, Gemini-N, Keck, Wise, Swift, the Allen Telescope Array, Combined Array for Research in Millimeter-wave Astronomy, Westerbork Synthesis Radio Telescope, and Expanded Very Large Array. Here we compare the properties of PTF 10bzf with those of SN 1998bw and other broad-line SNe. The optical luminosity and spectral properties of PTF 10bzf suggest that this SN is intermediate, in kinetic energy and amount of 56Ni, between non-GRB-associated SNe like 2002ap or 1997ef, and GRB-associated SNe like 1998bw. No X-ray or radio counterpart to PTF 10bzf was detected. X-ray upper limits allow us to exclude the presence of an underlying X-ray afterglow as luminous as that of other SN-associated GRBs such as GRB 030329 or GRB 031203. Early-time radio upper limits do not show evidence for mildly relativistic ejecta. Late-time radio upper limits rule out the presence of an underlying off-axis GRB, with energy and wind density similar to the SN-associated GRB 030329 and GRB 031203. Finally, by performing a search for a GRB in the time window and at the position of PTF 10bzf, we find that no GRB in the interplanetary network catalog could be associated with this SN. http://dx.doi.org/10.1088/0004-637X/741/2/76

Agüeros, Marcel A.; Covey, Kevin R.; Lemonias, Jenna J.; Law, Nicholas M.; Kraus, Adam; Batalha, Natasha; Bloom, Joshua S.; Cenko, S. Bradley; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Nugent, Peter E.; Ofek, Eran O.; Poznanski, Dovi; Quimby, Robert M.,"The Factory and the Beehive. I. Rotation Periods for Low-mass Stars in Praesepe",Astrophysical Journal,October 2011,740:110,

Stellar rotation periods measured from single-age populations are critical for investigating how stellar angular momentum content evolves over time, how that evolution depends on mass, and how rotation influences the stellar dynamo and the magnetically heated chromosphere and corona. We report rotation periods for 40 late-K to mid-M star members of the nearby, rich, intermediate-age (~600 Myr) open cluster Praesepe. These rotation periods were derived from ~200 observations taken by the Palomar Transient Factory of four cluster fields from 2010 February to May. Our measurements indicate that Praesepe's mass-period relation transitions from a well-defined singular relation to a more scattered distribution of both fast and slow rotators at ~0.6 M sun. The location of this transition is broadly consistent with expectations based on observations of younger clusters and the assumption that stellar spin-down is the dominant mechanism influencing angular momentum evolution at 600 Myr. However, a comparison to data recently published for the Hyades, assumed to be coeval to Praesepe, indicates that the divergence from a singular mass-period relation occurs at different characteristic masses, strengthening the finding that Praesepe is the younger of the two clusters. We also use previously published relations describing the evolution of rotation periods as a function of color and mass to evolve the sample of Praesepe periods in time. Comparing the resulting predictions to periods measured in M35 and NGC 2516 (~150 Myr) and for kinematically selected young and old field star populations suggests that stellar spin-down may progress more slowly than described by these relations. http://dx.doi.org/10.1088/0004-637X/740/2/110

Cano, Z.; Bersier, D.; Guidorzi, C.; Kobayashi, S.; Levan, A. J.; Tanvir, N. R.; Wiersema, K.; D'Avanzo, P.; Fruchter, A. S.; Garnavich, P.; Gomboc, A.; Gorosabel, J.; Kasen, D.; Kopač, D.; Margutti, R.; Mazzali, P. A.; Melandri, A.; Mundell, C. G.; Nugent, P. E.; Pian, E.; Smith, R. J.; Steele, I.; Wijers, R. A. M. J.; Woosley, S. E.,"XRF 100316D/SN 2010bh and the Nature of Gamma-Ray Burst Supernovae",Astrophysical Journal,October 2011,740:41,

We present ground-based and Hubble Space Telescope optical and infrared observations of Swift XRF 100316D/SN 2010bh. It is seen that the optical light curves of SN 2010bh evolve at a faster rate than the archetype gamma-ray burst supernova (GRB-SN) 1998bw, but at a similar rate to SN 2006aj, an SN that was spectroscopically linked with XRF 060218, and at a similar rate to the non-GRB associated Type Ic SN 1994I. We estimate the rest-frame extinction of this event from our optical data to be E(B - V) = 0.18 ± 0.08 mag. We find the V-band absolute magnitude of SN 2010bh to be MV = -18.62 ± 0.08, which is the faintest peak V-band magnitude observed to date for spectroscopically confirmed GRB-SNe. When we investigate the origin of the flux at t - t 0 = 0.598 days, it is shown that the light is not synchrotron in origin, but is likely coming from the SN shock breakout. We then use our optical and infrared data to create a quasi-bolometric light curve of SN 2010bh, which we model with a simple analytical formula. The results of our modeling imply that SN 2010bh synthesized a nickel mass of M Ni ≈ 0.1 M sun, ejected M ej ≈ 2.2 M sun, and has an explosion energy of E k ≈ 1.4 × 1052erg. Thus, while SN 2010bh is an energetic explosion, the amount of nickel created during the explosion is much less than that of SN 1998bw and only marginally more than SN 1994I. Finally, for a sample of 22 GRB-SNe we check for a correlation between the stretch factors and luminosity factors in the R band and conclude that no statistically significant correlation exists.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 11709. http://dx.doi.org/10.1088/0004-637X/740/1/41

Levitan, David; Fulton, Benjamin J.; Groot, Paul J.; Kulkarni, Shrinivas R.; Ofek, Eran O.; Prince, Thomas A.; Shporer, Avi; Bloom, Joshua S.; Cenko, S. Bradley; Kasliwal, Mansi M.; Law, Nicholas M.; Nugent, Peter E.; Poznanski, Dovi; Quimby, Robert M.; Horesh, Assaf; Sesar, Branimir; Sternberg, Assaf,"PTF1 J071912.13+485834.0: An Outbursting AM CVn System Discovered by a Synoptic Survey",Astrophysical Journal,October 2011,739:68,

We present extensive photometric and spectroscopic observations of PTF1 J071912.13+485834.0, an outbursting AM CVn system discovered by the Palomar Transient Factory (PTF). AM CVn systems are stellar binaries with some of the smallest separations known and orbital periods ranging from 5 to 65 minutes. They are believed to be composed of a white dwarf accretor and a (semi-)degenerate He-rich donor and are considered to be the helium equivalents of cataclysmic variables (CVs). We have spectroscopically and photometrically identified an orbital period of 26.77 ± 0.02 minutes for PTF1 J071912.13+485834.0 and found a super-outburst recurrence time of greater than 65 days along with the presence of "normal" outbursts—rarely seen in AM CVn systems but well known in super-outbursting CVs. We present a long-term light curve over two super-cycles as well as high-cadence photometry of both outburst and quiescent stages, both of which show clear variability. We also compare both the outburst and quiescent spectra of PTF1 J071912.13+485834.0 to other known AM CVn systems, and use the quiescent phase-resolved spectroscopy to determine the origin of the photometric variability. Finally, we draw parallels between the different subclasses of SU UMa-type CVs and outbursting AM CVn systems. We conclude by predicting that the PTF may more than double the number of outbursting AM CVn systems known, which would greatly increase our understanding of AM CVn systems. http://dx.doi.org/10.1088/0004-637X/739/2/68

Krisciunas, Kevin; Li, Weidong; Matheson, Thomas; Howell, D. Andrew; Stritzinger, Maximilian; Aldering, Greg; Berlind, Perry L.; Calkins, M.; Challis, Peter; Chornock, Ryan; Conley, Alexander; Filippenko, Alexei V.; Ganeshalingam, Mohan; Germany, Lisa; González, Sergio; Gooding, Samuel D.; Hsiao, Eric; Kasen, Daniel; Kirshner, Robert P.; Howie Marion, G. H.; Muena, Cesar; Nugent, Peter E.; Phelps, M.; Phillips, Mark M.; Qiu, Yulei; Quimby, Robert; Rines, K.; Silverman, Jeffrey M.; Suntzeff, Nicholas B.; Thomas, Rollin C.; Wang, Lifan,"The Most Slowly Declining Type Ia Supernova 2001ay",Astrophysical Journal,September 2011,142:74,

We present optical and near-infrared photometry, as well as ground-based optical spectra and Hubble Space Telescope ultraviolet spectra, of the Type Ia supernova (SN) 2001ay. At maximum light the Si II and Mg II lines indicated expansion velocities of 14,000 km s–1, while Si III and S II showed velocities of 9000 km s–1. There is also evidence for some unburned carbon at 12,000 km s–1. SN 2001ay exhibited a decline-rate parameter of Δm 15(B) = 0.68 ± 0.05 mag; this and the B-band photometry at t +25 day past maximum make it the most slowly declining Type Ia SN yet discovered. Three of the four super-Chandrasekhar-mass candidates have decline rates almost as slow as this. After correction for Galactic and host-galaxy extinction, SN 2001ay had MB = –19.19 and MV = –19.17 mag at maximum light; thus, it was not overluminous in optical bands. In near-infrared bands it was overluminous only at the 2σ level at most. For a rise time of 18 days (explosion to bolometric maximum) the implied 56Ni yield was (0.58 ± 0.15)/α M , with α = L max/E Ni probably in the range 1.0-1.2. The 56Ni yield is comparable to that of many Type Ia SNe. The "normal" 56Ni yield and the typical peak optical brightness suggest that the very broad optical light curve is explained by the trapping of γ rays in the inner regions. http://dx.doi.org/10.1088/0004-6256/142/3/74

Gal-Yam, Avishay; Kasliwal, Mansi M.; Arcavi, Iair; Green, Yoav; Yaron, Ofer; Ben-Ami, Sagi; Xu, Dong; Sternberg, Assaf; Quimby, Robert M.; Kulkarni, Shrinivas R.; Ofek, Eran O.; Walters, Richard; Nugent, Peter E.; Poznanski, Dovi; Bloom, Joshua S.; Cenko, S. Bradley; Filippenko, Alexei V.; Li, Weidong; Silverman, Jeffrey M.; Walker, Emma S.; Sullivan, Mark; Maguire, K.; Howell, D. Andrew; Mazzali, Paolo A.; Frail, Dale A.; Bersier, David; James, Phil A.; Akerlof, C. W.; Yuan, Fang; Law, Nicholas; Fox, Derek B.; Gehrels, Neil,"Real-time Detection and Rapid Multiwavelength Follow-up Observations of a Highly Subluminous Type II-P Supernova from the Palomar Transient Factory Survey",Astrophysical Journal,August 2011,736:159,

The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 deg2 field of view mounted on the 48 inch Oschin Schmidt telescope at Palomar Observatory. One of the key goals of this survey is to conduct high-cadence monitoring of the sky in order to detect optical transient sources shortly after they occur. Here, we describe the real-time capabilities of the PTF and our related rapid multiwavelength follow-up programs, extending from the radio to the γ-ray bands. We present as a case study observations of the optical transient PTF10vdl (SN 2010id), revealed to be a very young core-collapse (Type II-P) supernova having a remarkably low luminosity. Our results demonstrate that the PTF now provides for optical transients the real-time discovery and rapid-response follow-up capabilities previously reserved only for high-energy transients like gamma-ray bursts. http://dx.doi.org/10.1088/0004-637X/736/2/159

van Eyken, Julian C.; Ciardi, David R.; Rebull, Luisa M.; Stauffer, John R.; Akeson, Rachel L.; Beichman, Charles A.; Boden, Andrew F.; von Braun, Kaspar; Gelino, Dawn M.; Hoard, D. W.; Howell, Steve B.; Kane, Stephen R.; Plavchan, Peter; Ramírez, Solange V.; Bloom, Joshua S.; Cenko, S. Bradley; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Law, Nicholas M.; Nugent, Peter E.; Ofek, Eran O.; Poznanski, Dovi; Quimby, Robert M.; Grillmair, Carl J.; Laher, Russ; Levitan, David; Mattingly, Sean; Surace, Jason A.,"The Palomar Transient Factory Orion Project: Eclipsing Binaries and Young Stellar Objects",Astrophysical Journal,August 2011,142:60,

The Palomar Transient Factory (PTF) Orion project is one of the experiments within the broader PTF survey, a systematic automated exploration of the sky for optical transients. Taking advantage of the wide (35 × 23) field of view available using the PTF camera installed at the Palomar 48 inch telescope, 40 nights were dedicated in 2009 December to 2010 January to perform continuous high-cadence differential photometry on a single field containing the young (7-10 Myr) 25 Ori association. Little is known empirically about the formation of planets at these young ages, and the primary motivation for the project is to search for planets around young stars in this region. The unique data set also provides for much ancillary science. In this first paper, we describe the survey and the data reduction pipeline, and present some initial results from an inspection of the most clearly varying stars relating to two of the ancillary science objectives: detection of eclipsing binaries and young stellar objects. We find 82 new eclipsing binary systems, 9 of which are good candidate 25 Ori or Orion OB1a association members. Of these, two are potential young W UMa type systems. We report on the possible low-mass (M-dwarf primary) eclipsing systems in the sample, which include six of the candidate young systems. Forty-five of the binary systems are close (mainly contact) systems, and one of these shows an orbital period among the shortest known for W UMa binaries, at 0.2156509 ± 0.0000071 days, with flat-bottomed primary eclipses, and a derived distance that appears consistent with membership in the general Orion association. One of the candidate young systems presents an unusual light curve, perhaps representing a semi-detached binary system with an inflated low-mass primary or a star with a warped disk, and may represent an additional young Orion member. Finally, we identify 14 probable new classical T-Tauri stars in our data, along with one previously known (CVSO 35) and one previously reported as a candidate weak-line T-Tauri star (SDSS J052700.12+010136.8). http://dx.doi.org/10.1088/0004-6256/142/2/60

Levan, A. J.; Tanvir, N. R.; Cenko, S. B.; Perley, D. A.; Wiersema, K.; Bloom, J. S.; Fruchter, A. S.; Postigo, A. de Ugarte; O'Brien, P. T.; Butler, N.; van der Horst, A. J.; Leloudas, G.; Morgan, A. N.; Misra, K.; Bower, G. C.; Farihi, J.; Tunnicliffe, R. L.; Modjaz, M.; Silverman, J. M.; Hjorth, J.; Thöne, C.; Cucchiara, A.; Cerón, J. M. Castro; Castro-Tirado, A. J.; Arnold, J. A.; Bremer, M.; Brodie, J. P.; Carroll, T.; Cooper, M. C.; Curran, P. A.; Cutri, R. M.; Ehle, J.; Forbes, D.; Fynbo, J.; Gorosabel, J.; Graham, J.; Hoffman, D. I.; Guziy, S.; Jakobsson, P.; Kamble, A.; Kerr, T.; Kasliwal, M. M.; Kouveliotou, C.; Kocevski, D.; Law, N. M.; Nugent, P. E.; Ofek, E. O.; Poznanski, D.; Quimby, R. M.; Rol, E.; Romanowsky, A. J.; Sánchez-Ramírez, R.; Schulze, S.; Singh, N.; van Spaandonk, L.; Starling, R. L. C.; Strom, R. G.; Tello, J. C.; Vaduvescu, O.; Wheatley, P. J.; Wijers, R. A. M. J.; Winters, J. M.; Xu, D.,"An Extremely Luminous Panchromatic Outburst from the Nucleus of a Distant Galaxy",Science,July 2011,333:199-,

Variable x-ray and γ-ray emission is characteristic of the most extreme physical processes in the universe. We present multiwavelength observations of a unique γ-ray-selected transient detected by the Swift satellite, accompanied by bright emission across the electromagnetic spectrum, and whose properties are unlike any previously observed source. We pinpoint the event to the center of a small, star-forming galaxy at redshift z = 0.3534. Its high-energy emission has lasted much longer than any γ-ray burst, whereas its peak luminosity was ˜100 times higher than bright active galactic nuclei. The association of the outburst with the center of its host galaxy suggests that this phenomenon has its origin in a rare mechanism involving the massive black hole in the nucleus of that galaxy. http://dx.doi.org/10.1126/science.1207143

Kleiser, Io K. W.; Poznanski, Dovi; Kasen, Daniel; Young, Timothy R.; Chornock, Ryan; Filippenko, Alexei V.; Challis, Peter; Ganeshalingam, Mohan; Kirshner, Robert P.; Li, Weidong; Matheson, Thomas; Nugent, Peter E.; Silverman, Jeffrey M.,"Peculiar Type II supernovae from blue supergiants",Monthly Notices of the Royal Astronomical Society,July 2011,415:372-382,

The vast majority of Type II supernovae (SNeII) are produced by red supergiants, but SN 1987A revealed that blue supergiants (BSGs) can produce members of this class as well, albeit with some peculiar properties. This best-studied event revolutionized our understanding of SNe and linking it to the bulk of Type II events is essential. We present here the optical photometry and spectroscopy gathered for SN 2000cb, which is clearly not a standard SNII and yet is not a SN 1987A analogue. The light curve of SN 2000cb is reminiscent of that of SN 1987A in shape, with a slow rise to a late optical peak, but on substantially different time-scales. Spectroscopically, SN 2000cb resembles a normal SNII, but with ejecta velocities that far exceed those measured for SN 1987A or normal SNeII, above 18 000 km s−1 for Hα at early times. The red colours, high velocities, late photometric peak and our modelling of this object all point towards a scenario involving the high-energy explosion of a small-radius star, most likely a BSG, producing 0.1 M of 56Ni. Adding a similar object to the sample, SN 2005ci, we derive a rate of ∼2 per cent of the core-collapse rate for this loosely defined class of BSG explosions. http://dx.doi.org/10.1111/j.1365-2966.2011.18708.x

Quimby, R. M.; Kulkarni, S. R.; Kasliwal, M. M.; Gal-Yam, A.; Arcavi, I.; Sullivan, M.; Nugent, P.; Thomas, R.; Howell, D. A.; Nakar, E.; Bildsten, L.; Theissen, C.; Law, N. M.; Dekany, R.; Rahmer, G.; Hale, D.; Smith, R.; Ofek, E. O.; Zolkower, J.; Velur, V.; Walters, R.; Henning, J.; Bui, K.; McKenna, D.; Poznanski, D.; Cenko, S. B.; Levitan, D.,"Hydrogen-poor superluminous stellar explosions",Nature,June 2011,474:487-489,

Supernovae are stellar explosions driven by gravitational or thermonuclear energy that is observed as electromagnetic radiation emitted over weeks or more. In all known supernovae, this radiation comes from internal energy deposited in the outflowing ejecta by one or more of the following processes: radioactive decay of freshly synthesized elements (typically 56Ni), the explosion shock in the envelope of a supergiant star, and interaction between the debris and slowly moving, hydrogen-rich circumstellar material. Here we report observations of a class of luminous supernovae whose properties cannot be explained by any of these processes. The class includes four new supernovae that we have discovered and two previously unexplained events (SN 2005ap and SCP 06F6) that we can now identify as members of the same class. These supernovae are all about ten times brighter than most type Ia supernova, do not show any trace of hydrogen, emit significant ultraviolet flux for extended periods of time and have late-time decay rates that are inconsistent with radioactivity. Our data require that the observed radiation be emitted by hydrogen-free material distributed over a large radius (~1015 centimetres) and expanding at high speeds (>104 kilometres per second). These long-lived, ultraviolet-luminous events can be observed out to redshifts z>4.

Cano, Z.; Bersier, D.; Guidorzi, C.; Margutti, R.; Svensson, K. M.; Kobayashi, S.; Melandri, A.; Wiersema, K.; Pozanenko, A.; van der Horst, A. J.; Pooley, G. G.; Fernandez-Soto, A.; Castro-Tirado, A. J.; Postigo, A. De Ugarte; Im, M.; Kamble, A. P.; Sahu, D.; Alonso-Lorite, J.; Anupama, G.; Bibby, J. L.; Burgdorf, M. J.; Clay, N.; Curran, P. A.; Fatkhullin, T. A.; Fruchter, A. S.; Garnavich, P.; Gomboc, A.; Gorosabel, J.; Graham, J. F.; Gurugubelli, U.; Haislip, J.; Huang, K.; Huxor, A.; Ibrahimov, M.; Jeon, Y.; Jeon, Y.-B.; Ivarsen, K.; Kasen, D.; Klunko, E.; Kouveliotou, C.; Lacluyze, A.; Levan, A. J.; Loznikov, V.; Mazzali, P. A.; Moskvitin, A. S.; Mottram, C.; Mundell, C. G.; Nugent, P. E.; Nysewander, M.; O'Brien, P. T.; Park, W.-K.; Peris, V.; Pian, E.; Reichart, D.; Rhoads, J. E.; Rol, E.; Rumyantsev, V.; Scowcroft, V.; Shakhovskoy, D.; Small, E.; Smith, R. J.; Sokolov, V. V.; Starling, R. L. C.; Steele, I.; Strom, R. G.; Tanvir, N. R.; Tsapras, Y.; Urata, Y.; Vaduvescu, O.; Volnova, A.; Volvach, A.; Wijers, R. A. M. J.; Woosley, S. E.; Young, D. R.,"A tale of two GRB-SNe at a common redshift of z0.54",Monthly Notices of the Royal Astronomical Society,May 2011,413:669-685,

We present ground-based and Hubble Space Telescope optical observations of the optical transients (OTs) of long-duration Gamma Ray Bursts (GRBs) 060729 and 090618, both at a redshift of z= 0.54. For GRB 060729, bumps are seen in the optical light curves (LCs), and the late-time broad-band spectral energy distributions (SEDs) of the OT resemble those of local Type Ic supernovae (SNe). For GRB 090618, the dense sampling of our optical observations has allowed us to detect well-defined bumps in the optical LCs, as well as a change in colour, that are indicative of light coming from a core-collapse SN. The accompanying SNe for both events are individually compared with SN1998bw, a known GRB supernova, and SN1994I, a typical Type Ic supernova without a known GRB counterpart, and in both cases the brightness and temporal evolution more closely resemble SN1998bw. We also exploit our extensive optical and radio data for GRB 090618, as well as the publicly available Swift-XRT data, and discuss the properties of the afterglow at early times. In the context of a simple jet-like model, the afterglow of GRB 090618 is best explained by the presence of a jet-break at t-to > 0.5 d. We then compare the rest-frame, peak V-band absolute magnitudes of all of the GRB and X-Ray Flash (XRF)-associated SNe with a large sample of local Type Ibc SNe, concluding that, when host extinction is considered, the peak magnitudes of the GRB/XRF-SNe cannot be distinguished from the peak magnitudes of non-GRB/XRF SNe.

Childress, M.; Aldering, G.; Aragon, C.; Antilogus, P.; Bailey, S.; Baltay, C.; Bongard, S.; Buton, C.; Canto, A.; Chotard, N.; Copin, Y.; Fakhouri, H. K.; Gangler, E.; Kerschhaggl, M.; Kowalski, M.; Hsiao, E. Y.; Loken, S.; Nugent, P.; Paech, K.; Pain, R.; Pecontal, E.; Pereira, R.; Perlmutter, S.; Rabinowitz, D.; Runge, K.; Scalzo, R.; Thomas, R. C.; Smadja, G.; Tao, C.; Weaver, B. A.; Wu, C.,"Keck Observations of the Young Metal-poor Host Galaxy of the Super-Chandrasekhar-mass Type Ia Supernova SN 2007if",Astrophysical Journal,May 2011,733:3,

We present Keck LRIS spectroscopy and g-band photometry of the metal-poor, low-luminosity host galaxy of the super-Chandrasekhar-mass Type Ia supernova SN 2007if. Deep imaging of the host reveals its apparent magnitude to be mg = 23.15 ± 0.06, which at the spectroscopically measured redshift of z helio = 0.07450 ± 0.00015 corresponds to an absolute magnitude of Mg = -14.45 ± 0.06. Galaxy g - r color constrains the mass-to-light ratio, giving a host stellar mass estimate of log(M */M sun) = 7.32 ± 0.17. Balmer absorption in the stellar continuum, along with the strength of the 4000 Å break, constrains the age of the dominant starburst in the galaxy to be t burst = 123+165-77 Myr, corresponding to a main-sequence turnoff mass of M/M sun = 4.6+2.6-1.4. Using the R 23 method of calculating metallicity from the fluxes of strong emission lines, we determine the host oxygen abundance to be 12 + log(O/H)KK04 = 8.01 ± 0.09, significantly lower than any previously reported spectroscopically measured Type Ia supernova host galaxy metallicity. Our data show that SN 2007if is very likely to have originated from a young, metal-poor progenitor. http://dx.doi.org/10.1088/0004-637X/733/1/3

Barth, Aaron J.; Nguyen, My L.; Malkan, Matthew A.; Filippenko, Alexei V.; Li, Weidong; Gorjian, Varoujan; Joner, Michael D.; Bennert, Vardha Nicola; Botyanszki, Janos; Cenko, S. Bradley; Childress, Michael; Choi, Jieun; Comerford, Julia M.; Cucciara, Antonino; da Silva, Robert; Duchêne, Gaspard; Fumagalli, Michele; Ganeshalingam, Mohan; Gates, Elinor L.; Gerke, Brian F.; Griffith, Christopher V.; Harris, Chelsea; Hintz, Eric G.; Hsiao, Eric; Kandrashoff, Michael T.; Keel, William C.; Kirkman, David; Kleiser, Io K. W.; Laney, C. David; Lee, Jeffrey; Lopez, Liliana; Lowe, Thomas B.; Moody, J. Ward; Morton, Alekzandir; Nierenberg, A. M.; Nugent, Peter; Pancoast, Anna; Rex, Jacob; Rich, R. Michael; Silverman, Jeffrey M.; Smith, Graeme H.; Sonnenfeld, Alessandro; Suzuki, Nao; Tytler, David; Walsh, Jonelle L.; Woo, Jong-Hak; Yang, Yizhe; Zeisse, Carl,"Broad-line Reverberation in the Kepler-field Seyfert Galaxy Zw 229-015",Astrophysical Journal,May 2011,732:121,

The Seyfert 1 galaxy Zw 229-015 is among the brightest active galaxies being monitored by the Kepler mission. In order to determine the black hole mass in Zw 229-015 from Hβ reverberation mapping, we have carried out nightly observations with the Kast Spectrograph at the Lick 3 m telescope during the dark runs from 2010 June through December, obtaining 54 spectroscopic observations in total. We have also obtained nightly V-band imaging with the Katzman Automatic Imaging Telescope at Lick Observatory and with the 0.9 m telescope at the Brigham Young University West Mountain Observatory over the same period. We detect strong variability in the source, which exhibited more than a factor of two change in broad Hβ flux. From cross-correlation measurements, we find that the Hβ light curve has a rest-frame lag of 3.86+0.69-0.90 days with respect to the V-band continuum variations. We also measure reverberation lags for Hα and Hγ and find an upper limit to the Hδ lag. Combining the Hβ lag measurement with a broad Hβ width of σline = 1590 ± 47 km s-1 measured from the rms variability spectrum, we obtain a virial estimate of M BH = 1.00+0.19-0.24 × 107 M sun for the black hole in Zw 229-015. As a Kepler target, Zw 229-015 will eventually have one of the highest-quality optical light curves ever measured for any active galaxy, and the black hole mass determined from reverberation mapping will serve as a benchmark for testing relationships between black hole mass and continuum variability characteristics in active galactic nuclei.

Sullivan, M.; Kasliwal, M. M.; Nugent, P. E.; Howell, D. A.; Thomas, R. C.; Ofek, E. O.; Arcavi, I.; Blake, S.; Cooke, J.; Gal-Yam, A.; Hook, I. M.; Mazzali, P.; Podsiadlowski, P.; Quimby, R.; Bildsten, L.; Bloom, J. S.; Cenko, S. B.; Kulkarni, S. R.; Law, N.; Poznanski, D.,"The Subluminous and Peculiar Type Ia Supernova PTF 09dav",Astrophysical Journal,May 2011,732:118,

PTF 09dav is a peculiar subluminous Type Ia supernova (SN) discovered by the Palomar Transient Factory (PTF). Spectroscopically, it appears superficially similar to the class of subluminous SN1991bg-like SNe, but it has several unusual features which make it stand out from this population. Its peak luminosity is fainter than any previously discovered SN1991bg-like SN Ia (MB ~ -15.5), but without the unusually red optical colors expected if the faint luminosity were due to extinction. The photospheric optical spectra have very unusual strong lines of Sc II and Mg I, with possible Sr II, together with stronger than average Ti II and low velocities of ~6000 km s-1. The host galaxy of PTF09dav is ambiguous. The SN lies either on the extreme outskirts (~41 kpc) of a spiral galaxy or in an very faint (MR >= -12.8) dwarf galaxy, unlike other 1991bg-like SNe which are invariably associated with massive, old stellar populations. PTF 09dav is also an outlier on the light-curve-width-luminosity and color-luminosity relations derived for other subluminous SNe Ia. The inferred 56Ni mass is small (0.019 ± 0.003 M sun), as is the estimated ejecta mass of 0.36 M sun. Taken together, these properties make PTF 09dav a remarkable event. We discuss various physical models that could explain PTF 09dav. Helium shell detonation or deflagration on the surface of a CO white dwarf can explain some of the features of PTF 09dav, including the presence of Sc and the low photospheric velocities, but the observed Si and Mg are not predicted to be very abundant in these models. We conclude that no single model is currently capable of explaining all of the observed signatures of PTF 09dav. http://dx.doi.org/10.1088/0004-637X/732/2/118

Chotard, N.; Gangler, E.; Aldering, G.; Antilogus, P.; Aragon, C.; Bailey, S.; Baltay, C.; Bongard, S.; Buton, C.; Canto, A.; Childress, M.; Copin, Y.; Fakhouri, H. K.; Hsiao, E. Y.; Kerschhaggl, M.; Kowalski, M.; Loken, S.; Nugent, P.; Paech, K.; Pain, R.; Pecontal, E.; Pereira, R.; Perlmutter, S.; Rabinowitz, D.; Runge, K.; Scalzo, R.; Smadja, G.; Tao, C.; Thomas, R. C.; Weaver, B. A.; Wu, C.; Nearby Supernova Factory,"The reddening law of type Ia supernovae: separating intrinsic variability from dust using equivalent widths",Astronomy & Astrophysics,May 2011,529:L4,

We employ 76 type Ia supernovae (SNe Ia) with optical spectrophotometry within 2.5 days of B-band maximum light obtained by the Nearby Supernova Factory to derive the impact of Si and Ca features on the supernovae intrinsic luminosity and determine a dust reddening law. We use the equivalent width of Si ii λ4131 in place of the light curve stretch to account for first-order intrinsic luminosity variability. The resulting empirical spectral reddening law exhibits strong features that are associated with Ca ii and Si ii λ6355. After applying a correction based on the Ca ii H&K equivalent width we find a reddening law consistent with a Cardelli extinction law. Using the same input data, we compare this result to synthetic rest-frame UBVRI-like photometry to mimic literature observations. After corrections for signatures correlated with Si ii λ4131 and Ca ii H&K equivalent widths and introducing an empirical correlation between colors, we determine the dust component in each band. We find a value of the total-to-selective extinction ratio, RV = 2.8 ± 0.3. This agrees with the Milky Way value, in contrast to the low RVvalues found in most previous analyses. This result suggests that the long-standing controversy in interpreting SN Ia colors and their compatibility with a classical extinction law, which is critical to their use as cosmological probes, can be explained by the treatment of the dispersion in colors, and by the variability of features apparent in SN Ia spectra. http://dx.doi.org/1 0.1051/0004-6361/201116723

Miller, Adam A.; Hillenbrand, Lynne A.; Covey, Kevin R.; Poznanski, Dovi; Silverman, Jeffrey M.; Kleiser, Io K. W.; Rojas-Ayala, Bárbara; Muirhead, Philip S.; Cenko, S. Bradley; Bloom, Joshua S.; Kasliwal, Mansi M.; Filippenko, Alexei V.; Law, Nicholas M.; Ofek, Eran O.; Dekany, Richard G.; Rahmer, Gustavo; Hale, David; Smith, Roger; Quimby, Robert M.; Nugent, Peter; Jacobsen, Janet; Zolkower, Jeff; Velur, Viswa; Walters, Richard; Henning, John; Bui, Khanh; McKenna, Dan; Kulkarni, Shrinivas R.; Klein, Christopher R.; Kandrashoff, Michael; Morton, Alekzandir,"Evidence for an FU Orionis-like Outburst from a Classical T Tauri Star",Astrophysical Journal,April 1, 2011,730:80,

We present pre- and post-outburst observations of the new FU Orionis-like young stellar object PTF 10qpf (also known as LkHα 188-G4 and HBC 722). Prior to this outburst, LkHα 188-G4 was classified as a classical T Tauri star (CTTS) on the basis of its optical emission-line spectrum superposed on a K8-type photosphere and its photometric variability. The mid-infrared spectral index of LkHα 188-G4 indicates a Class II-type object. LkHα 188-G4 exhibited a steady rise by ~1 mag over ~11 months starting in August 2009, before a subsequent more abrupt rise of >3 mag on a timescale of ~2 months. Observations taken during the eruption exhibit the defining characteristics of FU Orionis variables: (1) an increase in brightness by gsim4 mag, (2) a bright optical/near-infrared reflection nebula appeared, (3) optical spectra are consistent with a G supergiant and dominated by absorption lines, the only exception being Hα which is characterized by a P Cygni profile, (4) near-infrared spectra resemble those of late K-M giants/supergiants with enhanced absorption seen in the molecular bands of CO and H2O, and (5) outflow signatures in H and He are seen in the form of blueshifted absorption profiles. LkHα 188-G4 is the first member of the FU Orionis-like class with a well-sampled optical to mid-infrared spectral energy distribution in the pre-outburst phase. The association of the PTF 10qpf outburst with the previously identified CTTS LkHα 188-G4 (HBC 722) provides strong evidence that FU Orionis-like eruptions represent periods of enhanced disk accretion and outflow, likely triggered by instabilities in the disk. The early identification of PTF 10qpf as an FU Orionis-like variable will enable detailed photometric and spectroscopic observations during its post-outburst evolution for comparison with other known outbursting objects. http://dx.doi.org/10.1088/0004-637X/730/2/80

December 31, 1969,

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J. Dongarra, et al.,"The International Exascale Software Project Roadmap",International Journal of High Performance Computing Applications,1969,doi: 25:1, 2011

J. Dongarra et al., “The International Exascale Software Project Roadmap,” International Journal of High Performance Computing Applications, 25:1, 2011

Conference Paper

Shane Canon, Doug Jacobsen,"Shifter: Containers for HPC",Cray User Group,London, England,May 13, 2016,

Container-based computed is rapidly changing the way software is developed, tested, and deployed. This paper builds on previously presented work on a prototype framework for running containers on HPC platforms. We will present a detailed overview of the design and implementation of Shifter, which in partnership with Cray has extended on the early prototype concepts and is now in production at NERSC. Shifter enables end users to execute containers using images constructed from various methods including the popular Docker-based ecosystem. We will discuss some of the improvements over the initial prototype including an improved image manager, integration with SLURM, integration with the burst buffer, and user controllable volume mounts. In addition, we will discuss lessons learned, performance results, and real-world use cases of Shifter in action. We will also discuss the potential role of containers in scientific and technical computing including how they complement the scientific process. We will conclude with a discussion about the future directions of Shifter.

Michael A. Purvis, Alexander Schafgans, Daniel J. W. Brown, Igor Fomenkov, Rob Rafac, Josh Brown, Yezheng Tao, Slava Rokitski, Mathew Abraham, Mike Vargas, Spencer Rich, Ted Taylor, David Brandt, Alberto Pirati, Aaron Fisher, Howard Scott, Alice Koniges, David Eder, Scott Wilks, Anthony Link, Steven Langer,"Advancements in predictive plasma formation modeling",Proc. SPIE 9776, Extreme Ultraviolet (EUV) Lithography VII, 97760K (March 18, 2016); doi:10.1117/12.2221991,March 18, 2016,

This modeling is performed to advance the rate of learning about optimal EUV generation for laser produced plasmas and to provide insights where experimental results are not currently available. The goal is to identify key physical processes necessary for an accurate and predictive model capable of simulating a wide range of conditions. This modeling will help to drive source performance scaling in support of the EUV Lithography roadmap. The model simulates pre-pulse laser interaction with the tin droplet and follows the droplet expansion into the main pulse target zone. Next, the interaction of the expanded droplet with the main laser pulse is simulated. We demonstrate the predictive nature of the code and provide comparison with experimental results. ALE-AMR and other codes are used for the modeling.

G. K. Lockwood, R. Wagner, M. Tatineni,"Storage utilization in the long tail of science",Proceedings of the 2015 XSEDE Conference,July 26, 2015,doi: 10.1145/2792745.2792777

The increasing expansion of computations in non-traditional domain sciences has resulted in an increasing demand for research cyberinfrastructure that is suitable for small- and mid-scale job sizes. The computational aspects of these emerging communities are coming into focus and being addressed through the deployment of several new XSEDE resources that feature easy on-ramps, customizable software environments through virtualization, and interconnects optimized for jobs that only use hundreds or thousands of cores; however, the data storage requirements for these emerging communities remains much less well characterized.

To this end, we examined the distribution of file sizes on two of the Lustre file systems within the Data Oasis storage system at the San Diego Supercomputer Center (SDSC). We found that there is a very strong preference for small files among SDSC's users, with 90% of all files being less than 2 MB in size. Furthermore, 50% of all file system capacity is consumed by files under 2 GB in size, and these distributions are consistent on both scratch and projects storage file systems. Because parallel file systems like Lustre and GPFS are optimized for parallel IO to large, widestripe files, these findings suggest that parallel file systems may not be the most suitable storage solutions when designing cyberinfrastructure to meet the needs of emerging communities.

Scott Campbell,"Open Science, Open Security",9th International Workshop on Security and High Performance Computing Systems,July 22, 2014,

We propose that to address the growing problems with complexity and data volumes in HPC security wee need to refactor how we look at data by creating tools that not only select data, but analyze and represent it in a manner well suited for intuitive analysis. We propose a set of rules describing what this means, and provide a number of production quality tools that represent our current best effort in implementing these ideas.

D. J. Choi, G. K. Lockwood, R. S. Sinkovits, M. Tatineni,"Performance of applications using dual-rail InfiniBand 3D torus network on the Gordon supercomputer",Proceedings of the 2014 XSEDE Conference,July 13, 2014,doi: 10.1145/2616498.2616541

Multi-rail InfiniBand networks provide options to improve bandwidth, increase reliability, and lower latency for multi-core nodes. The Gordon supercomputer at SDSC, with its dual-rail InfiniBand 3-D torus network, is used to evaluate the performance impact of using multiple rails. The study was performed using the OSU micro-benchmarks, the P3FFT application kernel, and scientific applications LAMMPS and AMBER. The micro-benchmarks confirmed the bandwidth and latency performance benefits. At the application level, performance improvements depended on the communication level and profile.

G. K. Lockwood, M. Tatineni, R. Wagner,"SR-IOV: Performance benefits for virtualized interconnects",Proceedings of the 2014 XSEDE Conference,July 13, 2014,doi: 10.1145/2616498.2616537

The demand for virtualization within high-performance computing is rapidly growing as new communities, driven by both new application stacks and new computing modalities, continue to grow and expand. While virtualization has traditionally come with significant penalties in I/O performance that have precluded its use in mainstream large-scale computing environments, new standards such as Single Root I/O Virtualization (SR-IOV) are emerging that promise to diminish the performance gap and make high-performance virtualization possible.

To this end, we have evaluated SR-IOV in the context of both virtualized InfiniBand and virtualized 10 gigabit Ethernet (GbE) using micro-benchmarks and real-world applications. We compare the performance of these interconnects on non-virtualized environments, Amazon's SR-IOV-enabled C3 instances, and our own SR-IOV-enabled InfiniBand cluster and show that SR-IOV significantly reduces the performance losses caused by virtualization. InfiniBand demonstrates less than 2% loss of bandwidth and less than 10% increase in latency when virtualized with SR-IOV. Ethernet also benefits, although less dramatically, when SR-IOV is enabled on Amazon's cloud.

J. A. Tracey, J. K. Sheppard, G. K. Lockwood, A. Chourasia, M. Tatineni, R. N. Fisher, R. S. Sinkovits,"Efficient 3D movement-based kernel density estimator and application to wildlife ecology",Proceedings of the 2014 XSEDE Conference,San Diego, CA,July 13, 2014,doi: 10.1145/2616498.2616541

We describe an efficient implementation of a 3D movement- based kernel density estimator for determining animal space use from discrete GPS measurements. This new method provides more accurate results, particularly for species that make large excursions in the vertical dimension. The downside of this approach is that it is much more computationally expensive than simpler, lower-dimensional models. Through a combination of code restructuring, parallelization and performance optimization, we were able to reduce the time to solution by up to a factor of 1000x, thereby greatly improving the applicability of the method.

S. Parete-Koon, B. Caldwell, S. Canon, E. Dart, J. Hick, J. Hill, C. Layton, D. Pelfrey, G. Shipman, D. Skinner, J. Wells, J. Zurawski,"HPC's Pivot to Data",Conference,May 5, 2014,

Computer centers such as NERSC and OLCF have traditionally focused on delivering computational capability that enables breakthrough innovation in a wide range of science domains. Accessing that computational power has required services and tools to move the data from input and output to computation and storage. A pivot to data is occurring in HPC. Data transfer tools and services that were previously peripheral are becoming integral to scientific workflows.  Emerging requirements from high-bandwidth detectors, highthroughput screening techniques, highly concurrent simulations, increased focus on uncertainty quantification, and an emerging open-data policy posture toward published research are among the data-drivers shaping the networks, file systems, databases, and overall HPC environment. In this paper we explain the pivot to data in HPC through user requirements and the changing resources provided by HPC with particular focus on data movement. For WAN data transfers we present the results of a study of network performance between centers

Jay Srinivasan, Richard Shane Canon,"Evaluation of A Flash Storage Filesystem on the Cray XE-6",CUG 2013,May 2013,

Flash storage and other solid-state storage technolo-gies are increasingly being considered as a way to address the growing gap between computation and I/O. Flash storage has a number of benefits such as good random read performance and lower power consumption. However, it has a number of challenges too, such as high cost and high-overhead for write operations. There are a number of ways Flash can be integrated into HPC systems. This paper will discuss some of the approaches and show early results for a Flash file system mounted on a Cray XE-6 using high-performance PCI-e based cards. We also discuss some of the gaps and challenges in integrating flash intoHPC systems and potential mitigations as well as new solid state storage technologies and their likely role in the future

Z. Liu, M. Veeraraghavan, Z. Yan, C. Tracyy, J. Tiez, I. Fosterz, J. Dennisx, J. Hick, Y. Lik and W. Yang,"On using virtual circuits for GridFTP transfers",Conference,November 12, 2012,

The goal of this work is to characterize scientific data transfers and to determine the suitability of dynamic virtual circuit service for these transfers instead of the currently used IP-routed service. Specifically, logs collected by servers executing a commonly used scientific data transfer application, GridFTP, are obtained from three US super-computing/scientific research centers, NERSC, SLAC, and NCAR, and analyzed. Dynamic virtual circuit (VC) service, a relatively new offering from providers such as ESnet and Internet2, allows for the selection of a path on which a rate-guaranteed connection is established prior to data transfer. Given VC setup overhead, the first analysis of the GridFTP transfer logs characterizes the duration of sessions, where a session consists of multiple back-to-back transfers executed in batch mode between the same two GridFTP servers. Of the NCAR-NICS sessions analyzed, 56% of all sessions (90% of all transfers) would have been long enough to be served with dynamic VC service. An analysis of transfer logs across four paths, NCAR-NICS, SLAC-BNL, NERSC-ORNL and NERSC-ANL, shows significant throughput variance, where NICS, BNL, ORNL, and ANL are other US national laboratories. For example, on the NERSC-ORNL path, the inter-quartile range was 695 Mbps, with a maximum value of 3.64 Gbps and a minimum value of 758 Mbps. An analysis of the impact of various factors that are potential causes of this variance is also presented.

Zacharia Fadika, Madhusudhan Govindaraju, Shane Richard Canon, Lavanya Ramakrishnan,"Evaluating Hadoop for Data-Intensive Scientific Operations",IEEE Cloud 2012,June 24, 2012,

Emerging sensor networks, more capable instruments, and ever increasing simulation scales are generating data at a rate that exceeds our ability to effectively manage, curate, analyze, and share it. Data-intensive computing is expected to revolutionize the next-generation software stack. Hadoop, an open source implementation of the MapReduce model provides a way for large data volumes to be seamlessly processed through use of large commodity computers. The inherent parallelization, synchronization and fault-tolerance the model offers, makes it ideal for highly-parallel data-intensive applications. MapReduce and Hadoop have traditionally been used for web data processing and only recently been used for scientific applications. There is a limited understanding on the performance characteristics that scientific data intensive applications can obtain from MapReduce and Hadoop. Thus, it is important to evaluate Hadoop specifically for data-intensive scientific operations -- filter, merge and reorder-- to understand its various design considerations and performance trade-offs. In this paper, we evaluate Hadoop for these data operations in the context of High Performance Computing (HPC) environments to understand the impact of the file system, network and programming modes on performance.

Jay Srinivasan, Richard Shane Canon, Lavanya Ramakrishnan,"My Cray can do that? Supporting Diverse Workloads on the Cray XE-6",CUG 2012,May 2012,

The Cray XE architecture has been optimized to support tightly coupled MPI applications, but there is an in- creasing need to run more diverse workloads in the scientific and technical computing domains. These needs are being driven by trends such as the increasing need to process “Big Data”. In the scientific arena, this is exemplified by the need to analyze data from instruments ranging from sequencers, telescopes, and X-ray light sources. These workloads are typically throughput oriented and often involve complex task dependencies. Can platforms like the Cray XE line play a role here? In this paper, we will describe tools we have developed to support high-throughput workloads and data intensive applications on NERSC’s Hopper system. These tools include a custom task farmer framework, tools to create virtual private clusters on the Cray, and using Cray’s Cluster Compatibility Mode (CCM) to support more diverse workloads. In addition, we will describe our experience with running Hadoop, a popular open-source implementation of MapReduce, on Cray systems. We will present our experiences with this work including successes and challenges. Finally, we will discuss future directions and how the Cray platforms could be further enhanced to support these class of workloads.

Scott Campbell, Jason Lee,"Prototyping a 100G Monitoring System",20th Euromicro International Conference on Parallel, Distributed, and Network-Based Processing (PDP 2012),February 12, 2012,

The finalization of the 100 Gbps Ethernet Specification has been a tremendous increase in these rates arriving into data centers creating the need to perform security monitoring at 100 Gbps no longer simply an academic exercise. We show that by leveraging the ‘heavy tail flow effect’ on the IDS infrastructure, it is possible to perform security analysis at such speeds within the HPC environment. Additionally, we examine the nature of current traffic characteristics, how to scale an IDS infrastructure to 100Gbps.

Scott Campbell, Jason Lee,"Intrusion Detection at 100G",The International Conference for High Performance Computing, Networking, Storage, and Analysis,November 14, 2011,

Driven by the growing data transfer needs of the scientific community and the standardization of the 100 Gbps Ethernet Specification, 100 Gbps is now becoming a reality for many HPC sites. This tenfold increase in bandwidth creates a number of significant technical challenges. We show that by using the heavy tail flow effect as a filter, it should be possible to perform active IDS analysis at this traffic rate using a cluster of commodity systems driven by a dedicated load balancing mechanism. Additionally, we examine the nature of current network traffic characteristics applying them to 100Gpbs speeds

Ghoshal, Devarshi and Canon, Richard Shane and Ramakrishnan, Lavanya,"Understanding I/O Performance of Virtualized Cloud Environments",The Second International Workshop on Data Intensive Computing in the Clouds (DataCloud-SC11),2011,

We compare the I/O performance using IOR benchmarks on two cloud computing platforms - Amazon and the Magellan cloud testbed.

Lavanya Ramakrishnan, Richard Shane Canon, Krishna Muriki, Iwona Sakrejda, and Nicholas J. Wright.,"Evaluating Interconnect and Virtualization Performance for High Performance Computing",Proceedings of 2nd International Workshop on Performance Modeling, Benchmarking and Simulation of High Performance Computing Systems (PMBS11),2011,

In this paper we detail benchmarking results that characterize the virtualization overhead and its impact on performance. We also examine the performance of various interconnect technologies with a view to understanding the performance impacts of various choices. Our results show that virtualization can have a significant impact upon performance, with at least a 60% performance penalty. We also show that less capable interconnect technologies can have a significant impact upon performance of typical HPC applications. We also evaluate the performance of the Amazon Cluster compute instance and show that it performs approximately equivalently to a 10G Ethernet cluster at low core counts.

K. Antypas, Y. He,"Transitioning Users from the Franklin XT4 System to the Hopper XE6 System",Cray User Group 2011 Procceedings,Fairbanks, Alaska,May 2011,

The Hopper XE6 system, NERSC’s first peta-flop system with over 153,000 cores has increased the computing hours available to the Department of Energy’s Office of Science users by more than a factor of 4. As NERSC users transition from the Franklin XT4 system with 4 cores per node to the Hopper XE6 system with 24 cores per node, they have had to adapt to a lower amount of memory per core and on- node I/O performance which does not scale up linearly with the number of cores per node. This paper will discuss Hopper’s usage during the “early user period” and examine the practical implications of running on a system with 24 cores per node, exploring advanced aprun and memory affinity options for typical NERSC applications as well as strategies to improve I/O performance.

P. M. Stewart, Y. He,"Benchmark Performance of Different Compilers on a Cray XE6",Fairbanks, AK,CUG Proceedings,May 23, 2011,

There are four different supported compilers on NERSC's recently acquired XE6, Hopper. Our users often request guidance from us in determining which compiler is best for a particular application. In this paper, we will describe the comparative performance of different compilers on several MPI benchmarks with different characteristics. For each compiler and benchmark, we will establish the best set of optimization arguments to the compiler.

Scott Campbell, Steve Chan and Jason Lee,"Detection of Fast Flux Service Networks",Australasian Information Security Conference 2011,January 17, 2011,

Fast Flux Service Networks (FFSN) utilize high availability server techniques for malware distribution. FFSNs are similar to commercial content distribution networks (CDN), such as Akamai, in terms of size, scope, and business model, serving as an outsourced content delivery service for clients.  Using an analysis of DNS traffic, we derive a sequential hypothesis testing algorithm based entirely on traffic characteristics and dynamic white listing to provide real time detection of FFDNs in live traffic.  We improve on existing work, providing faster and more accurate detection of FFSNs. We also identify a category of hosts not addressed in previous detectors - Open Content Distribution Networks (OCDN) that share many of the characteristics of FFSNs

Wendy Hwa-Chun Lin, Yun (Helen) He, and Woo-Sun Yang,"Franklin Job Completion Analysis",Cray User Group 2010 Proceedings,Edinburgh, UK,May 2010,

The NERSC Cray XT4 machine Franklin has been in production for 3000+ users since October 2007, where about 1800 jobs run each day. There has been an on-going effort to better understand how well these jobs run, whether failed jobs are due to application errors or system issues, and to further reduce system related job failures. In this paper, we talk about the progress we made in tracking job completion status, in identifying job failure root cause, and in expediting resolution of job failures, such as hung jobs, that are caused by system issues. In addition, we present some Cray software design enhancements we requested to help us track application progress and identify errors.

Yun (Helen) He,"User and Performance Impacts from Franklin Upgrades",Cray User Group Meeting 2009,Atlanta, GA,May 2009,LBNL 2013E,

The NERSC flagship computer Cray XT4 system "Franklin" has gone through three major upgrades: quad core upgrade, CLE 2.1 upgrade, and IO upgrade, during the past year.  In this paper, we will discuss the various aspects of the user impacts such as user access, user environment, and user issues etc from these upgrades. The performance impacts on the kernel benchmarks and selected application benchmarks will also be presented.

James M. Craw, Nicholas P. Cardo, Yun (Helen) He, and Janet M. Lebens,"Post-Mortem of the NERSC Franklin XT Upgrade to CLE 2.1",Cray User Group Meeting 2009,Atlanta, GA,May 2009,

This paper will discuss the lessons learned of the events leading up to the production deployment of CLE 2.1 and the post install issues experienced in upgrading NERSC's XT4 system called Franklin.

Yun (Helen) He, William T.C. Kramer, Jonathan Carter, and Nicholas Cardo,"Franklin: User Experiences",Cray User Group Meetin 2008,May 4, 2008,LBNL 2014E,

The newest workhorse of the National Energy Research Scientific Computing Center is a Cray XT4 with 9,736 dual core nodes. This paper summarizes Franklin user experiences from friendly early user period to production period. Selected successful user stories along with top issues affecting user experiences are presented.

Jonathan Carter, Yun (Helen) He, John Shalf, Hongzhang Shan, Erich Strohmaier, and Harvey Wasserman,"The Performance Effect of Multi-Core on Scientific Applications",Cray User Group 2007,May 2007,LBNL 62662,

The historical trend of increasing single CPU performance has given way to roadmap of increasing core count. The challenge of effectively utilizing these multi- core chips is just starting to be explored by vendors and application developers alike. In this study, we present some performance measurements of several complete scientific applications on single and dual core Cray XT3 and XT4 systems with a view to characterizing the effects of switching to multi-core chips. We consider effects within a node by using applications run at low concurrencies, and also effects on node- interconnect interaction using higher concurrency results. Finally, we construct a simple performance model based on the principle on-chip shared resource—memory bandwidth—and use this to predict the performance of the forthcoming quad-core system.

Book

A. Shoshani, D. Rotem,Scientific Data Management: Challenges, Technology, and Deployment,Book, (December 16, 2009)

This book provides a comprehensive understanding of the latest techniques for managing data during scientific exploration processes, from data generation to data analysis.

Book Chapter

Leonid Oliker, Jonathan Carter, V. Beckner, J. Bell, H. J. Wasserman, M. Adams, S. Ethier, and E. Schnetter,"Large-Scale Numerical Simulations on High-End Computational Platforms",Chapman & Hall/CRC Computational Science,edited by David H. Bailey, Robert F. Lucas, Samuel Williams, (Chapman & Hall/CRC Computational Science:November 23, 2010)

ISBN 9781439815694

John Shalf, S. Dosanjh, John Morrison,"Exascale Computing Technology Challenges",VECPAR, ( 2010) Pages: 1-25

High Performance Computing architectures are expected to change dramatically in the next decade as power and cooling constraints limit increases in microprocessor clock speeds. Consequently computer companies are dramatically increasing on-chip parallelism to improve performance. The traditional doubling of clock speeds every 18-24 months is being replaced by a doubling of cores or other parallelism mechanisms. During the next decade the amount of parallelism on a single microprocessor will rival the number of nodes in early massively parallel supercomputers that were built in the 1980s. Applications and algorithms will need to change and adapt as node architectures evolve. In particular, they will need to manage locality to achieve performance. A key element of the strategy as we move forward is the co-design of applications, architectures and programming environments. There is an unprecedented opportunity for application and algorithm developers to influence the direction of future architectures so that they meet DOE mission needs. This article will describe the technology challenges on the road to exascale, their underlying causes, and their effect on the future of HPC system design.

Presentation/Talk

Clayton Bagwell, Richard Gerber,NUG 2016 Business Meeting: Allocations,NUG Business Meeting presentation,March 24, 2016,

NUG (NERSC Users Group) Business meeting: Allocations

Clayton Bagwell,NUG 2016 New User Training - Accounts & Allocations,NUG New User Training presentation,March 21, 2016,

NUG (NERSC Users Group) New User Training; Accounts and Allocations

Clayton Bagwell, Richard Gerber,NERSC Brown Bag: Allocations,NERSC Brown Bag presentation,March 17, 2016,

Brown Bag presentation to NERSC staff on how Allocations work and the new scavenger queues.

J. Hick,Future Directions and How SPXXL Can Help,SPXXL Summer 2015,May 21, 2015,

Discussion of how NERSC may look in 2020, some challenges to getting there, and a proposal for how the SPXXL user group can help.

J. Hick, R. Lee, R. Cheema, K. Fagnan,GPFS for Life Sciences at NERSC,GPFS User Group Meeting,May 20, 2015,

A report showing both high and low-level changes made to our life sciences workloads to support them on GPFS file systems.

Richard A. Gerber,Performance and Debugging Tools for HPC,February 17, 2015,

Guest lecture in UC Berkeley CS 267 - Applications of Parallel Computers

Richard A. Gerber,Exascale Computing, Big Data, and World-Class Science at NERSC,November 13, 2014,

Talk given at San Jose State University Physics Department colloquium on Nov. 13, 2014.

J. Hick,Scalability Challenges in Large-Scale Tape Environments,IEEE Mass Storage Systems & Technologies 2014,June 4, 2014,

Provides an overview of NERSC storage systems and focuses on challenges we experience with HPSS at NERSC and with the tape industry.

Larry Pezzaglia,Cluster Consolidation at NERSC,A talk at the HEPiX Spring 2014 Workshop, Annecy-le-Vieux, France,May 22, 2014,

In 2012, NERSC began deployment of "Mendel", a 500+ node, Infiniband-attached, Linux "meta-cluster" which transparently expands NERSC production clusters and services in a scalable and maintainable fashion. The success of the software automation infrastructure behind the Mendel multi-clustering model encouraged investigation into even more aggressive consolidation efforts.

This talk will detail one such effort: under the constraints of a 24x7, disruption-sensitive environment, NERSC staff merged a 400-node legacy production cluster, consisting of multiple hardware generations and ad-hoc software configurations, into Mendel's automation infrastructure. By leveraging the hierarchical management features of the xCAT software package in combination with other open-source and in-house tools, such as Cfengine and CHOS, NERSC abstracted the unique characteristics of both clusters away below a unified management interface. Consequently, both cluster components are now managed as a single, albeit complex, integrated system.

Additionally, this talk will provide an update on the PDSF system at NERSC, including improvements to trending data collection and ongoing CHOS development.

Pavan Balaji, Alice Koniges, Robert Harrison, Tim Mattson, Nick Wright, David Bernholdt,Application Grand Challenges in the Heterogeneous Accelerator Era,SC13 Birds of a Feather: Invited Panelist,November 21, 2013,

Accelerators have gained prominence as the next disruptive technology with a potential to provide a non-incremental jump in performance. However, the number of applications that have actually moved to accelerators is still limited because of many reasons, arguably the biggest of which is the gap in understanding between accelerator and application developers. This BoF is an application oriented session that aims to bring the two camps of application developers and accelerator developers head-to-head.

Tim Mattson, Alice Koniges, Simon McIntosh-Smith,OpenCL: A Hands-On Introduction,SC13 Tutorial,November 18, 2013,

OpenCL is an open standard for programming heterogeneous parallel computers composed of CPUs, GPUs and other processors. OpenCL consists of a framework to manipulate the host CPU and one or more compute devices (CPUs, GPUs or accelerators), and a C-based programming language for writing programs for the compute devices. Using OpenCL, a programmer can write parallel programs that harness all of the resources of a heterogeneous computer. In this hands-on tutorial, we will introduce OpenCL. For ease of learning we will focus on the easier to use C++ API, but attendees will also gain an understanding of OpenCLs C API. The format will be a 50/50 split between lectures and exercises. Students will use their own laptops (Windows, Linux or OS/X) and log into a remote server running an OpenCL platform on a range of different processors. Alternatively, students can load OpenCL onto their own laptops prior to the course (Intel, AMD and NVIDIA provide OpenCL SDKs. Apple laptops with X-code include OpenCL by default). By the end of the course, attendees will be able to write and optimize OpenCL programs, and will have a collection of example codes to help with future OpenCL program development.

N. Balthaser,GlobusOnline/HPSS Live Demo,HUF 2013,November 5, 2013,

Live demonstration using the GlobusOnline data transfer software to store files to the NERSC archive for 2013 HPSS Users Forum meeting.

N. Balthaser,LBNL/NERSC Site Report: HPSS in Production,HUF 2013,November 5, 2013,

Overview of HPSS infrastructure and practices at LBNL/NERSC for 2013 HPSS Users Forum meeting.

J. Hick,A Storage Outlook for Energy Sciences: Data Intensive, Throughput and Exascale Computing,FujiFilm Executive IT Summit 2013,October 24, 2013,

Provides an overview of the computational and storage systems at NERSC.  Discusses the major types of computation scientists conduct at the facility, the challenges and opportunities the storage systems will face in the near future, and the role of tape technology at the Center.

Trever Nightingale,Introduction to Google Chromebooks,LBL Tech Day Lightning Talk,October 10, 2013,

Introduction to Google Chromebooks.  The good parts reviewers often leave out.

Clayton Bagwell,How to Submit a 2014 ERCAP Request,September 16, 2013,

Video presentation and accompanying PowerPoint slides on "How to Submit a 2014 ERCAP Request".

Joaquin Correa,Integrated Tools for NGBI--Lessons Learned and Successful Cases,LBNL Integrated Bioimaging Initiative,September 4, 2013,

NextGen Bioimaging (NGBI) requires a reliable and flexible solution for multi-modal, high-throughput and high-performance image processing and analysis. In order to solve this challenge, we have developed an OMERO-based modular and flexible platform that integrates a suite of general-purpose processing software, a set of custom-tailored algorithms, specific bio-imaging applications and NERSC's high performance computing resources and its science gateways.
This under-development platform provides a shared scalable one-stop-shop web-service for producers and consumers of models built on imaging data to refine pixel data into actionable knowledge resources.

Richard Gerber,Introduction to High Performance Computing,June 10, 2013,

Introduction to High Performance Computing presented to Berkeley Lab Computing Sciences summer interns.

N. Balthaser, W. Hurlbert,T10KC Technology in Production,May 9, 2013,

Report to 2012  Large Tape User Group meeting regarding our production statistics and experiences using the Oracle T10000C tape drive.

J. Hick,Storage at a Distance,Open Fabrics Alliance User Day 2013,April 19, 2013,

Presentation to generate discussion on current state-of-the-practice for the topic of storage at a distance and synergy with Open Fabrics Alliance users.

Richard Gerber,NUG March 2013 Webinar,March 7, 2013,

NERSC User Group Teleconference and Webinar Slides for March 7, 2013

Richard A. Gerber,Debugging and Optimization Tools,February 19, 2013,

Debugging and Optimization Tools, presented for UC Berkeley CS267 "Applications of Parallel Computers" class, Feb. 19, 2013.

Richard A. Gerber, Tina Declerck. Zhengji Zhao,Edison Update,February 12, 2013,

Overview and update on the installation and configuration of Edison, NERSC's new Cray XC30 supercomputer.

Richard A. Gerber, Harvey Wasserman,NERSC Requirements Reviews,February 12, 2013,

An update on the NERSC Requirements Reviews at NUG 2013. Richard Gerber and Harvey Wasserman, NERSC>

Katie Antypas,NERSC-8 Project,NUG Meeting,February 12, 2013,

NERSC-8 Project Overview

Richard A. Gerber,Getting Started at NERSC,January 17, 2013,

Getting Started at NERSC Webinar, January 17, 2013, Richard Gerber, NERSC User Services

J. Hick,GPFS at NERSC/LBNL,SPXXL Winter 2013,January 7, 2013,

A report to SPXXL conference participants on state of the NERSC Global File System architecture, achievements and directions.

Richard A. Gerber,Uses for High Performance Computing,June 12, 2012,

Who uses High Peformance Computing and what do they do with it? Presented for LBNL Summer Interns, June 12, 2012.

Richard A. Gerber,Introduction to High Performance Computers,June 12, 2012,

Introduction for High Performance Computers. Presented to LBNL Summer Interns, June 12, 2012.

Richard A. Gerber,Challenges in HPC,June 12, 2012,

Challenges in High Performance Computing. Presented to LBNL Summer Interns, June 12, 2012.

N. Balthaser, J. Hick, W. Hurlbert,StorageTek Tape Analytics: Pre-Release Evaluation at LBNL,LTUG 2012,April 25, 2012,

A report to the Large Tape Users Group (LTUG) annual conference on a pre-release evaluation of the new software product, StorageTek Tape Analytics (STA).  We provide a user's perspective on what we found useful, some suggestions for improvement, and some key new features that would enhance the product.

Larry Pezzaglia,CHOS in Production: Supporting Multiple Linux Environments on PDSF at NERSC,A talk at the HEPiX Spring 2012 Workshop, Prague, Czech Republic,April 25, 2012,

The CHOS[1] software package combines a Linux kernel module, a PAM module, and batch system integration to provide a mechanism for concurrently supporting multiple Linux environments on a single Linux system. This presentation gives an introduction to CHOS and details how NERSC has deployed this utility on the PDSF HPC system to meet the complex, and often conflicting, software environment requirements of multiple applications. The CHOS utility has been in continuous use on PDSF for over 8 years, and has proven to be a robust and simple approach to ensure optimal software environments for HENP workloads.

[1] CHOS was written by Shane Canon of NERSC, and the code is available on GitHub. The CHOS technology is explained in detail in this paper.

Eric Hjort, Larry Pezzaglia, Iwona Sakrejda,PDSF at NERSC: Site Report,A talk at the HEPiX Spring 2012 Workshop, Prague, Czech Republic,April 24, 2012,

PDSF is a commodity Linux cluster at NERSC which has been in continuous operation since 1996. This talk will provide a status update on the PDSF system and summarize recent changes at NERSC. Highlighted PDSF changes include the conversion to xCAT-managed netboot node images, the ongoing deployment of Scientific Linux 6, and the introduction of XRootD for STAR.

Richard Shane Canon,Magellan Project: Clouds for Science?,Coalition for Academic Scientific Computation,February 29, 2012,

This presentation gives a brief overview of the Magellan Project and some of its findings.

J. Hick,NERSC Site Update (NGF),SPXXL Winter 2012,January 10, 2012,

Update to NERSC Global File (NGF) System, based on IBM's GPFS, to the SPXXL User Group community.  Includes an overview of NERSC, the file systems that comprise NGF, some of our experiences with GPFS, and recommendations for improving scalability.

M. Cary, J. Hick, A. Powers,HPC Archive Solutions Made Simple,Half-day Tutorial at Super Computing (SC11),November 13, 2011,

Half-day tutorial at SC11 where attendees were provided detailed information about HPC archival storage systems for general education.  The tutorial was the first SC tutorial to cover the topic of archival storage and helped sites to understand the characteristics of these systems, the terminology for archives, and how to plan, size and manage these systems.

Cherri M. Pancake, Debra Goldfarb, Alice Koniges, Candy Culhane,The View, HPC Edition,SC11 Panel,November 2011,

This panel will be a take-off on ABC's popular morning talk program. A lively format will be used to cover a number of controversial topics in the development and application of HPC. Four women from the HPC world will serve as "co-hosts," discussing topics with international experts associated with specific topics, such as Jean-Yves Berthou (European Exascale Software Initiative), Dave Turek (IBM), Ryan Waite (Microsoft), and Matt Fetes (venture capitalist). The goal is to air a variety of viewpoints in a lively and entertaining way. The panel will raise thought-provoking questions such as why the HPC community has such a hard time converging on standards, whether co-design is really affordable at HPC scales, why efficiency isn't our goal rather than scalability, whether exascale investments can really pay off, and why high-level languages haven't had real impact in HPC. Interactive polling will be used to involve the audience in charting a course for HPC's future - so be sure to bring your laptop or smartphone.

J. Hick,Digital Archiving and Preservation in Government Departments and Agencies,Oracle Open World 2011,October 6, 2011,

Attendees of this invited talk at Oracle Open World 2011 heard about the NERSC Storage Systems Group and the HPSS Archive and Backup systems we manage.  Includes information on why we use disk and tape to store data, and an introduction to the Large Tape Users Group (LTUG).

Lavanya Ramakrishnan & Shane Canon, NERSC,Hadoop and Pig Overview,October 2011,

The MapReduce programming model and its open source implementation Hadoop is gaining traction in the scientific community for addressing the needs of data focused scientific applications. The requirements of these scientific applications are significantly different from the web 2.0 applications that have  traditionally used Hadoop. The tutorial  will provide an overview of Hadoop technologies, discuss some use cases of Hadoop for science and present the programming challenges with using Hadoop for legacy applications. Participants will access the Hadoop system at NERSC for the hands-on component of the tutorial.

J. Hick,The NERSC Global Filesystem (NGF),Computing in Atmospheric Sciences 2011 (CAS2K11),September 13, 2011,

Provides the Computing in Atmospheric Sciences 2011 conference attendees an overview and configuration details of the NERSC Global Filesystem (NGF).  Includes a few lessons learned and future directions for NGF.

Shane Canon,Debunking Some Common Misconceptions of Science in the Cloud,ScienceCloud 2011,June 29, 2011,

This presentation addressed five common misconceptions of cloud computing including: clouds are simple to use and don’t require system administrators; my job will run immediately in the cloud; clouds are more efficient; clouds allow you to ride Moore’s Law without additional investment; commercial Clouds are much cheaper than operating your own system.

T. Nightingale,No Cost ZFS On Low Cost Hardware,NERSC High Performance Computing Seminar,June 14, 2011,

Today's data generation rates and terabyte hard drives have led to a new breed of commodity servers that have very large filesystems. This talk looks at the implications and describes the decision to deploy ZFS under FreeBSD on NERSC servers. Included will be a look at pertinent ZFS features, configuration decisions adopted, experiences with ZFS so far, and how we are using the features ZFS brings with it to gain some new functionality that was not possible with previous filesystems.

J. Hick, M. Andrews,Leveraging the Business Value of Tape,FujiFilm Executive IT Summit 2011,June 9, 2011,

Describes how tape is used in the HPSS Archive and HPSS Backup systems at NERSC.  Includes some examples of our organizations tape policies, our roadmap to Exascale and an example of tape in the Exascale Era, our observed tape reliability, and an overview of our locally developed Parallel Incremental Backup System (PIBS) which performs backups of our NGF file system.

J. Hick,Storage Supporting DOE Science,Preservation and Archiving Special Interest Group (PASIG) 2011,May 12, 2011,

Provided attendees of the Preservation and Archiving Special Interest Group conference attendees with an overview of NERSC, the Storage Systems Group, and the HPSS Archives and NGF File Systems we support.  Includes some information on a large tape data migration and our observations on the reliability of tape at NERSC.

D. Hazen, J. Hick, W. Hurlbert, M. Welcome,Media Information Record (MIR) Analysis,LTUG 2011,April 19, 2011,

Presentation of Storage Systems Group findings from a year-long effort to collect and analyze Media Information Record (MIR) statistics from our in-production Oracle enterprise tape drives at NERSC.  We provide information on the data collected, and some highlights from our analysis. The presentation is primarily intended to declare that the information in the MIR is important to users or customers to better operating and managing their tape environments.

J. Hick,I/O Requirements for Exascale,Open Fabrics Alliance 2011,April 4, 2011,

This talk provides an overview of the DOE Exascale effort, high level IO requirements, and an example of exascale era tape storage.

D. Hazen, J. Hick,HPSS v8 Metadata Conversion,HPSS 8.1 Pre-Design Meeting,April 7, 2010,

Provided information about the HPSS metadata conversion software to other developers of HPSS.  Input was important to establishing a design for the version 8 HPSS metadata conversions.

Richard Shane Canon,Cosmic Computing: Supporting the Science of the Planck Space Based Telescope,LISA 2009,November 5, 2009,

The scientific community is creating data at an ever-increasing rate. Large-scale experimental devices such as high-energy collider facilities and advanced telescopes generate petabytes of data a year. These immense data streams stretch the limits of the storage systems and of their administrators. The Planck project, a space-based telescope designed to study the Cosmic Microwave Background, is a case in point. Launched in May 2009, the Planck satellite will generate a data stream requiring a network of storage and computational resources to store and analyze the data. This talk will present an overview of the Planck project, including the motivation and mission, the collaboration, and the terrestrial resources supporting it. It will describe the data flow and network of computer resources in detail and will discuss how the various systems are managed. Finally, it will highlight some of the present and future challenges in managing a large-scale data system.

J. Hick,Sun StorageTek Tape Hardware Migration Experiences,LTUG 2009,April 24, 2009,

Talk addresses specific experiences and lessons learned in migrating our entire HPSS archive from StorageTek 9310 Powderhorns using 9840A, 9940B, and T10KA tape drives to StorageTek SL8500 Libraries using 9840D and T10KB tape drives.

Report

Massimiliano Albanese, Michael Berry, David Brown, Scott Campbell, Stephen Crago, George Cybenko, Jon DeLapp, Christopher L. DeMarco, Jeff Draper, Manuel Egele, Stephan Eidenbenz, Tina Eliassi-Rad, Vergle Gipson, Ryan Goodfellow, Paul Hovland, Sushil Jajodia, Cliff Joslyn, Alex Kent, Sandy Landsberg, Larry Lanes, Carolyn Lauzon, Steven Lee, Sven Leyffer, Robert Lucas, David Manz, Celeste Matarazzo, Jackson R. Mayo, Anita Nikolich, Masood Parvania, Garrett Payer, Sean Peisert, Ali Pinar, Thomas Potok, Stacy Prowell, Eric Roman, David Sarmanian, Dylan Schmorrow, Chris Strasburg, V.S. Subrahmanian, Vipin Swarup, Brian Tierney, Von Welch,"ASCR Cybersecurity for Scientific Computing Integrity",DOE Workshop Report,January 7, 2015,

At the request of the U.S. Department of Energy’s (DOE) Advanced Scientific Computing Research (ASCR) program, a workshop was held January 7–9, 2015, in Rockville, Md., to examine computer security research gaps and approaches for assuring scientific computing integrity specific to the mission of the DOE Office of Science. Issues included research computation and simulation that takes place on ASCR computing facilities and networks, as well as network-connected scientific instruments, such as those run by other DOE Office of Science programs. Workshop participants included researchers and operational staff from DOE national laboratories, as well as academic researchers and industry experts. Participants were selected based on the prior submission of abstracts relating to the topic. Additional input came from previous DOE workshop reports [DOE08,BB09] relating to security. Several observers from DOE and the National Science Foundation also attended.

Fox W., Correa J., Cholia S., Skinner D., Ophus C.,"NCEM Hub, A Science Gateway for Electron Microscopy in Materials Science",LBNL Tech Report on NCEMhub,May 1, 2014,

Electron microscopy (EM) instrumentation is making a detector-driven transition to Big Data. High capability cameras bring new resolving power but also an exponentially increasing demand for bandwidth and data analysis. In practical terms this means that users of advanced microscopes find it increasingly challenging to take data with them and instead need an integrated data processing pipeline. in 2013 NERSC and NCEM staff embarked on a pilot to prototype data services that provide such a pipeline. This tech report details the NCEM Hub pilot as it concluded in May 2014.

Damian Hazen, Jason Hick,"MIR Performance Analysis",June 12, 2012,LBNL LBNL-5896E,

We provide analysis of Oracle StorageTek T10000 Generation B (T10KB) Media Information Record (MIR) Per- formance Data gathered over the course of a year from our production High Performance Storage System (HPSS). The analysis shows information in the MIR may be used to improve tape subsystem operations. Most notably, we found the MIR information to be helpful in determining whether the drive or tape was most suspect given a read or write error, and for helping identify which tapes should not be reused given their history of read or write errors. We also explored using the MIR Assisted Search to order file retrieval requests. We found that MIR Assisted Search may be used to reduce the time needed to retrieve collections of files from a tape volume.

Richard A. Gerber, Harvey J. Wasserman,"Large Scale Computing and Storage Requirements for Nuclear Physics",Workshop,March 26, 2012,LBNL LBNL-5355E,

Report of the user requirements workshop for lattice gauge theory and nuclear physics computation at NERSC that took place May 26, 2011

J. Hick, J. Hules, A. Uselton,"DOE HPC Best Practices Workshop: File Systems and Archives",Workshop,September 27, 2011,

The Department of Energy has identified the design, implementation, and usability of file systems and archives as key issues for current and future HPC systems. This workshop addresses current best practices for the procurement, operation, and usability of file systems and archives. Furthermore, the workshop addresses whether system challenges can be met by evolving current practices.

N. Balthaser, D. Hazen,"HSI Best Practices for NERSC Users",May 2, 2011,LBNL 4745E,

In this paper we explain how to obtain and install HSI, create a NERSC authentication token, and transfer data to and from the system. Additionally we describe methods to optimize data transfers and avoid common pitfalls that can degrade data transfers and storage system performance.

W. Allcock, R. Carlson, S. Cotter, E. Dart, V. Dattoria, B. Draney, R. Gerber, M. Helm, J. Hick, S. Hicks, S. Klasky, M. Livny, B. Maccabe, C. Morgan, S. Morss, L. Nowell, D. Petravick, J. Rogers, Y. Sekine, A. Sim, B. Tierney, S. Turnbull, D. Williams, L. Winkler, F. Wuerthwein,"ASCR Science Network Requirements",Workshop,April 15, 2009,

ESnet publishes reports from Network and Science Requirement Workshops on a regular basis.  This report was the product of a two-day workshop in Washington DC that addresses science requirements impacting operations of networking for 2009.

A. Mokhtarani, W. Kramer, J. Hick,"Reliability Results of NERSC Systems",Web site,August 28, 2008,

In order to address the needs of future scientific applications for storing and accessing large amounts of data in
an efficient way, one needs to understand the limitations of current technologies and how they may cause system
instability or unavailability. A number of factors can impact system availability ranging from facility-wide
power outage to a single point of failure such as network switches or global file systems. In addition, individual
component failure in a system can degrade the performance of that system. This paper focuses on analyzing both
of these factors and their impacts on the computational and storage systems at NERSC. Component failure data
presented in this report primarily focuses on disk drive in on of the computational system and tape drive failure
in HPSS. NERSC collected available component failure data and system-wide outages for its computational and
storage systems over a six-year period and made them available to the HPC community through the Petascale
Data Storage Institute.

Antypas, K., Shalf, J., Wasserman, H.,"NERSC‐6 Workload Analysis and Benchmark Selection Process",LBNL Technical Report,August 13, 2008,LBNL 1014E,

Science drivers for NERSC-6

J. Levesque, J. Larkin, M. Foster, J. Glenski, G. Geissler, S. Whalen, B. Waldecker, J. Carter, D. Skinner, H. He, H. Wasserman, J. Shalf, H. Shan,"Understanding and mitigating multicore performance issues on the AMD opteron architecture",March 1, 2007,LBNL 62500,

Over the past 15 years, microprocessor performance has doubled approximately every 18 months through increased clock rates and processing efficiency. In the past few years, clock frequency growth has stalled, and microprocessor manufacturers such as AMD have moved towards doubling the number of cores every 18 months in order to maintain historical growth rates in chip performance. This document investigates the ramifications of multicore processor technology on the new Cray XT4systems based on AMD processor technology. We begin by walking through the AMD single-core and dual-core and upcoming quad-core processor architectures. This is followed by a discussion of methods for collecting performance counter data to understand code performance on the Cray XT3and XT4systems. We then use the performance counter data to analyze the impact of multicore processors on the performance of microbenchmarks such as STREAM, application kernels such as the NAS Parallel Benchmarks, and full application codes that comprise the NERSC-5 SSP benchmark suite. We explore compiler options and software optimization techniques that can mitigate the memory bandwidth contention that can reduce computing efficiency on multicore processors. The last section provides a case study of applying the dual-core optimizations to the NAS Parallel Benchmarks to dramatically improve their performance.1

E. Wes Bethel, Scott Campbell, Eli Dart, Jason Lee, Steven A. Smith, Kurt Stockinger, Brian Tierney, Kesheng Wu,"Interactive Analysis of Large Network Data Collections Using Query-Driven Visualization",DOE Report,September 26, 2006,LBNL 59166,

Realizing operational analytics solutions where large and complex data must be analyzed in a time-critical fashion entails integrating many different types of technology. Considering the extreme scale of contemporary datasets, one significant challenge is to reduce the duty cycle in the analytics discourse process. This paper focuses on an interdisciplinary combination of scientific data management and visualization/analysistechnologies targeted at reducing the duty cycle in hypothesis testing and knowledge discovery. We present an application of such a combination in the problem domain of network traffic dataanalysis. Our performance experiment results, including both serial and parallel scalability tests, show that the combination can dramatically decrease the analytics duty cycle for this particular application. The combination is effectively applied to the analysis of network traffic data to detect slow and distributed scans, which is a difficult-to-detect form of cyberattack. Our approach is sufficiently general to be applied to a diverse set of data understanding problems as well as used in conjunction with a diverse set of analysis and visualization tools