S. R. Kulkarni

Publications (289)1310.29 Total impact

• Article: Discovery of a Cosmological, Relativistic Outburst via its Rapidly Fading Optical Emission

  S. Bradley Cenko, S. R. Kulkarni, Assaf Horesh, Alessandra Corsi, Derek B. Fox, John Carpenter, Dale A. Frail, Peter E. Nugent, Daniel A. Perley, D. Gruber, [......], Mansi M. Kasliwal, Nicholas M. Law, Adam N. Morgan, David Polishook, Dovi Poznanski, Robert M. Quimby, Branimir Sesar, Ken J. Shen, Jeffrey M. Silverman, Assaf Sternberg
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  ABSTRACT: We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright, rapidly fading optical transient emission; (2) a faint, blue quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients, and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are all consistent with the population of long-duration gamma-ray bursts (GRBs), marking the first time such an outburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible high-energy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an "untriggered" GRB (lack of satellite coverage), an "orphan" afterglow (viewing-angle effects), and a "dirty fireball" (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-duration GRB for which the associated high-energy emission was simply missed. However, we have calculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (~ 2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (> 4 times the on-axis GRB rate at 90% confidence) class of relativistic outbursts lacking associated high-energy emission.
  04/2013;
• Article: Supernova 2009ex-2009fh and Possible Supernovae K0905-1, K0905-2, K0905-3

  M. M. Kasliwal, S. R. Kulkarni, R. Quimby, P. E. Nugent, D. A. Howell, J. Cooke, S. B. Cenko, A. Gal-Yam, N. Law, D. Levitan, E. O. Ofek, D. Poznanski
  Central Bureau Electronic Telegrams. 02/2013; 1819:1.
• Article: An outburst from a massive star 40 days before a supernova explosion.

  E O Ofek, M Sullivan, S B Cenko, M M Kasliwal, A Gal-Yam, S R Kulkarni, I Arcavi, L Bildsten, J S Bloom, A Horesh, D A Howell, A V Filippenko, R Laher, D Murray, E Nakar, P E Nugent, J M Silverman, N J Shaviv, J Surace, O Yaron
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  ABSTRACT: Some observations suggest that very massive stars experience extreme mass-loss episodes shortly before they explode as supernovae, as do several models. Establishing a causal connection between these mass-loss episodes and the final explosion would provide a novel way to study pre-supernova massive-star evolution. Here we report observations of a mass-loss event detected 40 days before the explosion of the type IIn supernova SN 2010mc (also known as PTF 10tel). Our photometric and spectroscopic data suggest that this event is a result of an energetic outburst, radiating at least 6 × 10(47) erg of energy and releasing about 10(-2) solar masses of material at typical velocities of 2,000 km s(-1). The temporal proximity of the mass-loss outburst and the supernova explosion implies a causal connection between them. Moreover, we find that the outburst luminosity and velocity are consistent with the predictions of the wave-driven pulsation model, and disfavour alternative suggestions.
  Nature 02/2013; 494(7435):65-7. · 36.28 Impact Factor
• Article: Millions of Multiples: Detecting and Characterizing Close-Separation Binary Systems in Synoptic Sky Surveys

  Emil Terziev, Nicholas M. Law, Iair Arcavi, Christoph Baranec, Joshua S. Bloom, Khanh Bui, Mahesh P. Burse, Pravin Chorida, H. K. Das, Richard G. Dekany, Adam L. Kraus, S. R. Kulkarni, Peter Nugent, Eran O. Ofek, Sujit Punnadi, A. N. Ramaprakash, Reed Riddle, Shriharsh P. Tendulkar
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  ABSTRACT: The direct detection of binary systems in wide-field surveys is limited by the size of the stars' point-spread-functions (PSFs). A search for elongated objects can find closer companions, but is limited by the precision to which the PSF shape can be calibrated for individual stars. We have developed the BinaryFinder algorithm to search for close binaries by using precision measurements of PSF ellipticity across wide-field survey images. We show that the algorithm is capable of reliably detecting binary systems down to approximately 1/5 of the seeing limit, and can directly measure the systems' position angles, separations and contrast ratios. To verify the algorithm's performance we evaluated 100,000 objects in Palomar Transient Factory (PTF) wide-field-survey data for signs of binarity, and then used the Robo-AO robotic laser adaptive optics system to verify the parameters of 44 high-confidence targets. We show that BinaryFinder correctly predicts the presence of close companions with a <5% false-positive rate, measures the detected binaries' position angles within 2 degrees and separations within 25%, and weakly constrains their contrast ratios. When applied to the full PTF dataset, we estimate that BinaryFinder will discover and characterize ~450,000 physically-associated binary systems with separations <2 arcseconds and magnitudes brighter than R=18. New wide-field synoptic surveys with high sensitivity and sub-arcsecond angular resolution, such as LSST, will allow BinaryFinder to reliably detect millions of very faint binary systems with separations as small as 0.1 arcseconds.
  10/2012;
• Article: An Early & Comprehensive Millimeter and Centimeter Wave and X-ray Study of Supernova 2011dh: A Non-Equipartition Blastwave Expanding into A Massive Stellar Wind

  Assaf Horesh, Christopher Stockdale, Derek B. Fox, Dale A. Frail, John Carpenter, S. R. Kulkarni, Eran O. Ofek, Avishay Gal-Yam, Mansi M. Kasliwal, Iair Arcavi, [......], David Polishook, Ofer Yaron, Stuart Ryder, Kurt W. Weiler, Franz Bauer, Schuyler D. Van Dyk, Stefan Immler, Nino Panagia, Dave Pooley, Namir Kassim
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  ABSTRACT: Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, starting a few days after explosion. The early detection and classification of the nearby type IIb SN2011dh/PTF11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12 after explosion) in the radio, millimeter and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding supernova shockwave does not exhibit equipartition (e_e/e_B ~ 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R^-2. Within modeling uncertainties we find an average velocity of the fast parts of the ejecta of 15,000 +/- 1800 km/s, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast-wave regime between the previously defined compact and extended SN IIb subtypes. Our results highlight the importance of early (~ 1 day) high-frequency observations of future events. Moreover, we show the importance of combined radio/X-ray observations for determining the microphysics ratio e_e/e_B.
  09/2012;
• Article: PTF 11kx: a type Ia supernova with a symbiotic nova progenitor.

  B Dilday, D A Howell, S B Cenko, J M Silverman, P E Nugent, M Sullivan, S Ben-Ami, L Bildsten, M Bolte, M Endl, [......], D R Tytler, D Xu, J S Bloom, A Gal-Yam, I M Hook, S R Kulkarni, N M Law, E O Ofek, D Polishook, D Poznanski
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  ABSTRACT: There is a consensus that type Ia supernovae (SNe Ia) arise from the thermonuclear explosion of white dwarf stars that accrete matter from a binary companion. However, direct observation of SN Ia progenitors is lacking, and the precise nature of the binary companion remains uncertain. A temporal series of high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex circumstellar environment that provides an unprecedentedly detailed view of the progenitor system. Multiple shells of circumstellar material are detected, and the SN ejecta are seen to interact with circumstellar material starting 59 days after the explosion. These features are best described by a symbiotic nova progenitor, similar to RS Ophiuchi.
  Science 08/2012; 337(6097):942-5. · 31.20 Impact Factor
• Article: The UV/optical spectra of the Type Ia supernova SN 2010jn: a bright supernova with outer layers rich in iron-group elements

  S. Hachinger, P. A. Mazzali, M. Sullivan, R. Ellis, K. Maguire, A. Gal-Yam, D. A. Howell, P. E. Nugent, E. Baron, J. Cooke, [......], B. Dilday, P. A. James, M. M. Kasliwal, S. R. Kulkarni, E. O. Ofek, R. R. Laher, J. Parrent, J. Surace, O. Yaron, E. S. Walker
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  ABSTRACT: Radiative transfer studies of Type Ia supernovae (SNe Ia) hold the promise of constraining both the time-dependent 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 present a detailed analysis of Hubble Space Telescope ultraviolet (UV) and ground-based optical spectra and light curves of the SN Ia SN 2010jn (PTF10ygu). SN 2010jn was discovered by the Palomar Transient Factory (PTF) 15 days before maximum light, allowing us to secure a time-series of four UV spectra at epochs from -11 to +5 days relative to B-band maximum. The photospheric 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 have derived 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.
  08/2012;
• Article: PTF11kx: A Type-Ia Supernova with a Symbiotic Nova Progenitor

  B. Dilday, D. A. Howell, S. B. Cenko, J. M. Silverman, P. E. Nugent, M. Sullivan, S. Ben-Ami, L. Bildsten, M. Bolte, M. Endl, [......], D. R. Tytler, D. Xu, J. S. Bloom, A. Gal-Yam, I. M. Hook, S. R. Kulkarni, N. M. Law, E. O. Ofek, D. Polishook, D. Poznanski
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  ABSTRACT: There is a consensus that Type-Ia supernovae (SNe Ia) arise from the thermonuclear explosion of white dwarf stars that accrete matter from a binary companion. However, direct observation of SN Ia progenitors is lacking, and the precise nature of the binary companion remains uncertain. A temporal series of high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex circumstellar environment that provides an unprecedentedly detailed view of the progenitor system. Multiple shells of circumsteller are detected and the SN ejecta are seen to interact with circumstellar material (CSM) starting 59 days after the explosion. These features are best described by a symbiotic nova progenitor, similar to RS Ophiuchi.
  07/2012;
• Article: Aperture Photometry Tool Versus SExtractor for Noncrowded Fields

  R ~R Laher, L ~M Rebull, V Gorjian, F ~J Masci, J ~W Fowler, C Grillmair, J Surace, S Mattingly, E Jackson, E Hacopeans, [......], R ~M Quimby, E ~O Ofek, M ~M Kasliwal, J Zolkower, V Velur, R Walters, J Henning, K Bui, D McKenna, S ~R Kulkarni
  pasp. 07/2012; 124:764-781.
• Article: The Palomar Transient Factory photometric catalog 1.0

  E. O. Ofek, R. Laher, J. Surace, D. Levitan, B. Sesar, A. Horesh, N. Law, J. C. van Eyken, S. R. Kulkarni, T. A. Prince, [......], I. Arcavi, L. Bildsten, J. Bloom, S. B. Cenko, A. Gal-Yam, C. Grillmair, G. Helou, M. M. Kasliwal, D. Poznanski, R. Quimby
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  ABSTRACT: We construct a photometrically calibrated catalog of non-variable sources from the Palomar Transient Factory (PTF) observations. The first version of this catalog presented here, the PTF photometric catalog 1.0, contains calibrated R_PTF-filter magnitudes for about 21 million sources brighter than magnitude 19, over an area of about 11233 deg^2. The magnitudes are provided in the PTF photometric system, and the color of a source is required in order to convert these magnitudes into other magnitude systems. We estimate that the magnitudes in this catalog have typical accuracy of about 0.02 mag with respect to magnitudes from the Sloan Digital Sky Survey. The median repeatability of our catalog's magnitudes for stars between 15 and 16 mag, is about 0.01 mag, and it is better than 0.03 mag for 95% of the sources in this magnitude range. The main goal of this catalog is to provide reference magnitudes for photometric calibration of visible light observations. Subsequent versions of this catalog, which will be published incrementally online, will be extended to a larger sky area and will also include g_PTF-filter magnitudes, as well as variability and proper motion information.
  06/2012;
• Article: X-ray emission from supernovae in dense circumstellar matter environments: A search for collisionless shocks

  E. O. Ofek, D. Fox, S. B. Cenko, M. Sullivan, O. Gnat, D. A. Frail, A. Horesh, A. Corsi, R. M. Quimby, N. Gehrels, [......], A. V. Filippenko, M. M. Kasliwal, L. Bildsten, J. S. Bloom, D. Poznanski, I. Arcavi, R. R. Laher, D. Levitan, B. Sesar, J. Surace
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  ABSTRACT: (Abridged). The optical light curve of some SNe may be powered by the outward diffusion of the energy deposited by the explosion shock in optically thick circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and -dominated shock in an optically thick wind must transform into a collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM (IIn/Ibn/SLSN-I). Two SNe in our sample have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSM. Therefore, we suggest that their optical light curves are powered by shock breakout in CSM. We show that two other events were too X-ray bright during the SN maximum optical light to be explained by the shock breakout model. We conclude that the light curves of some, but not all, type-IIn/Ibn SNe are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all the SLSN-I events, our X-ray limits are not deep enough and were typically obtained at too early times to conclude about their nature. We argue that the optical light curves of SNe, for which the X-ray emission peaks at late times, are likely powered by the diffusion of shock energy from a dense CSM. We comment about the possibility to detect some of these events in radio.
  06/2012;
• Article: Two Distant Halo Velocity Groups Discovered by the Palomar Transient Factory

  B. Sesar, J. G. Cohen, D. Levitan, C. J. Grillmair, M. Juric, E. N. Kirby, R. R. Laher, E. O. Ofek, J. A. Surace, S. R. Kulkarni, T. A. Prince
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  ABSTRACT: We report the discovery of two new halo velocity groups (Cancer groups A and B) traced by 8 distant RR Lyrae stars and observed by the Palomar Transient Factory (PTF) survey at R.A.~129 deg, Dec~20 deg (l~205 deg, b~32 deg). Located at 92 kpc from the Galactic center (86 kpc from the Sun), these are some of the most distant substructures in the Galactic halo known to date. Follow-up spectroscopic observations with the Palomar Observatory 5.1-m Hale telescope and W. M. Keck Observatory 10-m Keck I telescope indicate that the two groups are moving away from the Galaxy at v_{gsr} = 78.0+-5.6 km/s (Cancer group A) and v_{gsr} = 16.3+-7.1 km/s (Cancer group B). The groups have velocity dispersions of \sigma_{v_{gsr}}=12.4+-5.0 km/s and \sigma_{v_{gsr}}=14.9+-6.2 km/s, and are spatially extended (about several kpc) making it very unlikely that they are bound systems, and are more likely to be debris of tidally disrupted dwarf galaxies or globular clusters. Both groups are metal-poor (median metallicities of [Fe/H] = -1.6 dex and [Fe/H] =-2.1 dex), and have a somewhat uncertain (due to small sample size) metallicity dispersion of ~0.4 dex, suggesting dwarf galaxies as progenitors. Two additional RR Lyrae stars with velocities consistent with those of the Cancer groups have been observed ~25 deg east, suggesting possible extension of the groups in that direction.
  06/2012;
• Article: Analysis of the Early-Time Optical Spectra of SN 2011fe in M101

  J. T. Parrent, D. A. Howell, B. Friesen, R. C. Thomas, R. A. Fesen, D. Milisavljevic, F. B. Bianco, B. Dilday, P. Nugent, E. Baron, [......], D. Polishook, D. Poznanski, R. M. Quimby, J. M. Silverman, A. Sternberg, M. Sullivan, E. S. Walker, D. Xu, C. Buton, R. Pereira
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  ABSTRACT: The nearby Type Ia supernova SN 2011fe in M101 (cz=241 km s^-1) provides a unique opportunity to study the early evolution of a "normal" Type Ia supernova, 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 7774 absorption features detected within five days post-explosion indicate 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.
  05/2012;
• Source

  Available from: ArXiv

  Article: Cosmic Explosions (Optical Transients)

  S. R. Kulkarni
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  ABSTRACT: This paper is an extended summary of the talk I gave at IAU Symposium "New Horizons in Time Domain Astronomy" (Oxford, 2011). I first review the history of transients (which is intimately related to the advent of wide-field telescopic imaging; I then summarize wide field imaging projects. The motivations that led to the design of the Palomar Transient Factory (PTF) followed by a summary of the astronomical returns from PTF. I review the lessons learnt from PTF. I conclude that, during this decade, optical transient searches will continue to flourish and may even accelerate as surveys at other wavelengths -- notably radio, UV and X-ray -- come on line. As a result, I venture to suggest that specialized searches for transients will continue -- even into the LSST era. I end the article by discussing the importance of follow-up telescopes for transient object studies -- a topical issue given that in the US the Portfolio Review is under away.
  02/2012;
• Source

  Available from: ArXiv

  Article: Evidence for a Compact Wolf-Rayet Progenitor for the Type Ic Supernova PTF 10vgv

  A. Corsi, E. O. Ofek, A. Gal-Yam, D. A. Frail, D. Poznanski, P. A. Mazzali, S. R. Kulkarni, M. M. Kasliwal, I. Arcavi, S. Ben-Ami, [......], I. K. W. Kleiser, E. Nakar, I. Rabinak, R. Sari, J. M. Silverman, D. Xu, J. S. Bloom, N. M. Law, P. E. Nugent, and R. M. Quimby
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  ABSTRACT: We present the discovery of PTF 10vgv, a Type Ic supernova (SN) detected by the Palomar Transient Factory, using the Palomar 48 inch telescope (P48). R-band observations of the PTF 10vgv field with P48 probe the SN emission from its very early phases (about two weeks before R-band maximum) and set limits on its flux in the week prior to the discovery. Our sensitive upper limits and early detections constrain the post-shock-breakout luminosity of this event. Via comparison to numerical (analytical) models, we derive an upper-limit of R 4.5 R ☉ (R 1 R ☉) on the radius of the progenitor star, a direct indication in favor of a compact Wolf-Rayet star. Applying a similar analysis to the historical observations of SN 1994I yields R 1/4 R ☉ for the progenitor radius of this SN.
  The Astrophysical Journal Letters 02/2012; 747(1):L5. · 5.53 Impact Factor
• Article: Early Radio and X-Ray Observations of the Youngest nearby Type Ia Supernova PTF 11kly (SN 2011fe)

  Assaf Horesh, S. R. Kulkarni, Derek B. Fox, John Carpenter, Mansi M. Kasliwal, Eran O. Ofek, Robert Quimby, Avishay Gal-Yam, S. Bradley Cenko, A. G. de Bruyn, [......], Chryssa Kouveliotou, Philipp Podsiadlowski, Mark Sullivan, Kate Maguire, D. Andrew Howell, Peter E. Nugent, Neil Gehrels, Nicholas M. Law, Dovi Poznanski, and Michael Shara
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  ABSTRACT: On 2011 August 24 (UT) the Palomar Transient Factory (PTF) discovered PTF11kly (SN 2011fe), the youngest and most nearby Type Ia supernova (SN Ia) in decades. We followed this event up in the radio (centimeter and millimeter bands) and X-ray bands, starting about a day after the estimated explosion time. We present our analysis of the radio and X-ray observations, yielding the tightest constraints yet placed on the pre-explosion mass-loss rate from the progenitor system of this supernova. We find a robust limit of from sensitive X-ray non-detections, as well as a similar limit from radio data, which depends, however, on assumptions about microphysical parameters. We discuss our results in the context of single-degenerate models for SNe Ia and find that our observations modestly disfavor symbiotic progenitor models involving a red giant donor, but cannot constrain systems accreting from main-sequence or sub-giant stars, including the popular supersoft channel. In view of the proximity of PTF11kly and the sensitivity of our prompt observations, we would have to wait for a long time (a decade or longer) in order to more meaningfully probe the circumstellar matter of SNe Ia.
  The Astrophysical Journal 01/2012; 746(1):21. · 6.02 Impact Factor
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  Available from: ArXiv

  Article: Classical Novae in Andromeda: Light Curves from the Palomar Transient Factory and GALEX

  Yi Cao, Mansi M. Kasliwal, James D. Neill, S. R. Kulkarni, Yu-Qing Lou, Sagi Ben-Ami, Joshua S. Bloom, S. Bradley Cenko, Nicholas M. Law, Peter E. Nugent, Eran O. Ofek, Dovi Poznanski, Robert M. Quimby
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  ABSTRACT: We present optical light curves of twenty-nine novae in M31 during the 2009 and 2010 observing seasons of the Palomar Transient Factory (PTF). The dynamic and rapid cadences in PTF monitoring of M31, from one day to even ten minutes, provide excellent temporal coverage of nova light curves, enabling us to record the photometric evolution of M31 novae in unprecedented detail. We also detect eight of these novae in the near ultraviolet (UV) band with the Galaxy Evolution Explorer (GALEX) satellite. Novae M31N2009-10b and 2010-11a show prominent UV emission peaking a few days prior to their optical maxima, possibly implying aspherical outbursts. Additionally, our blue-shifted spectrum of the recent outburst of PT And (M31N2010-12a) indicates that it is a recurrent nova in M31 and not a dwarf nova in the Milky Way as was previously assumed. Finally, we systematically searched for novae in all confirmed globular clusters of M31 and found only M31N 2010-10f associated with Bol 126. The specific nova rate in the M31 globular cluster system is thus about one per year which is not enhanced relative to the rate outside the globular cluster system.
  01/2012;
• Source

  Available from: Noah Brosch

  Article: Asteroid rotation periods from the Palomar Transient Factory survey

  D. Polishook, E. O. Ofek, A. Waszczak, S. R. Kulkarni, A. Gal-Yam, O. Aharonson, R. Laher, J. Surace, C. Klein, J. Bloom, N. Brosch, D. Prialnik, C. Grillmair, S. B. Cenko, M. Kasliwal, N. Law, D. Levitan, P. Nugent, D. Poznanski, R. Quimby
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  ABSTRACT: The Palomar Transient Factory (PTF) is a synoptic survey designed to explore the transient and variable sky in a wide variety of cadences. We use PTF observations of fields that were observed multiple times (>=10) per night, for several nights, to find asteroids, construct their lightcurves and measure their rotation periods. Here we describe the pipeline we use to achieve these goals and present the results from the first four (overlapping) PTF fields analyzed as part of this program. These fields, which cover an area of 21 deg^2, were observed on four nights with a cadence of ~20 min. Our pipeline was able to detect 624 asteroids, of which 145 (~20%) were previously unknown. We present high quality rotation periods for 88 main-belt asteroids and possible period or lower limit on the period for an additional 85 asteroids. For the remaining 451 asteroids, we present lower limits on their photometric amplitudes. Three of the asteroids have lightcurves that are characteristic of binary asteroids. We estimate that implementing our search for all existing high-cadence PTF data will provide rotation periods for about 10,000 asteroids mainly in the magnitude range ~14 to ~20.
  01/2012;
• Source

  Available from: C. J. Grillmair

  Article: The Palomar Transient Factory photometric calibration

  E. O. Ofek, R. Laher, N. Law, J. Surace, D. Levitan, B. Sesar, A. Horesh, D. Poznanski, J. C. van Eyken, S. R. Kulkarni, [......], M Sullivan, M. Agueros, L. Bildsten, J. Bloom, S. B. Cenko, A. Gal-Yam, C. Grillmair, G. Helou, M. M. Kasliwal, R. Quimby
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  ABSTRACT: The Palomar Transient Factory (PTF) provides multiple epoch imaging for a large fraction of the sky. Here we describe the photometric calibration of the PTF data products that relates the PTF magnitudes to other mag systems. The calibration process utilizes SDSS r~16 mag point source objects as photometric standards. During photometric conditions, this allows us to solve for the extinction coefficients and color terms, and to estimate the camera illumination correction. This also enables the calibration of fields that are outside the SDSS footprint. We test the precision and repeatability of the PTF photometric calibration. Given that PTF is observing in a single filter each night, we define a PTF calibrated magnitude system for R-band and g-band. We show that, in this system, 59% (47%) of the photometrically calibrated PTF R-band (g-band) data achieve a photometric precision of 0.02-0.04 mag. Given the objects' color, the PTF magnitude system can be converted to other systems. A night-by-night comparison of the calibrated magnitudes of individual stars observed on multiple nights shows that they are consistent to a level of ~0.02 mag. Most of the data that were taken under non-photometric conditions can be calibrated relative to other epochs of the same sky footprint obtained during photometric conditions. We provide a guide describing the use of the PTF photometric calibration data products, as well as the transformations between the PTF magnitude system and the SDSS and Johnson-Cousins systems. (abridged).
  12/2011;
• Article: Supernova SN 2011fe from an exploding carbon-oxygen white dwarf star.

  Peter E Nugent, Mark Sullivan, S Bradley Cenko, Rollin C Thomas, Daniel Kasen, D Andrew Howell, David Bersier, Joshua S Bloom, S R Kulkarni, Michael T Kandrashoff, [......], Mansi M Kasliwal, Nicholas M Law, Robert M Quimby, Isobel M Hook, Emma S Walker, Paolo Mazzali, Elena Pian, Eran O Ofek, Avishay Gal-Yam, Dovi Poznanski
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  ABSTRACT: 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.
  Nature 12/2011; 480(7377):344-7. · 36.28 Impact Factor