Showing papers by "Peter Nugent published in 2011"
California Institute of Technology1, Weizmann Institute of Science2, University of Oxford3, Lawrence Berkeley National Laboratory4, Las Cumbres Observatory Global Telescope Network5, University of California, Santa Barbara6, Tel Aviv University7, Kavli Institute for Theoretical Physics8, University of California, San Diego9, University of Toronto10, University of California, Berkeley11
TL;DR: Observations of a class of luminous supernovae whose properties cannot be explained by any of the following processes: radioactive decay of freshly synthesized elements, explosion shock in the envelope of a supergiant star, and interaction between the debris and slowly moving, hydrogen-rich circumstellar material.
Abstract: 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 ^(56)Ni), 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 (~10^(15) centimetres) and expanding at high speeds (>10^4 kilometres per second). These long-lived, ultraviolet-luminous events can be observed out to redshifts z > 4.
615 citations
University of California, Berkeley1, Lawrence Berkeley National Laboratory2, University of Oxford3, Las Cumbres Observatory Global Telescope Network4, University of California, Santa Barbara5, Liverpool John Moores University6, California Institute of Technology7, Dartmouth College8, University of Toronto9, University of Tokyo10, Scuola Normale Superiore di Pisa11, Max Planck Society12, Weizmann Institute of Science13, Tel Aviv University14
TL;DR: Early observations of type Ia supernova SN 2011fe in the galaxy M101 at a distance from Earth of 6.4 megaparsecs find that the exploding star was probably a carbon–oxygen white dwarf, and from the lack of an early shock it is concluded that the companion was likely a main-sequence star.
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.
558 citations
University of Warwick1, University of Leicester2, University of California, Berkeley3, Space Telescope Science Institute4, University of Copenhagen5, Universities Space Research Association6, Columbia University7, Spanish National Research Council8, University of California, Santa Cruz9, University of California, Irvine10, French Alternative Energies and Atomic Energy Commission11, California Institute of Technology12, Swinburne University of Technology13, Johns Hopkins University14, University of Iceland15, University of Wisconsin–Milwaukee16, Marshall Space Flight Center17, University of Toronto18, Lawrence Berkeley National Laboratory19, University of Amsterdam20, National University of Ireland, Galway21, University of Hertfordshire22, ASTRON23, Weizmann Institute of Science24
TL;DR: 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 are presented.
Abstract: 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.
404 citations
University of California, Berkeley1, University of Oxford2, Rutgers University3, University of California, Santa Barbara4, Las Cumbres Observatory Global Telescope Network5, Lawrence Berkeley National Laboratory6, Arizona State University7, Weizmann Institute of Science8, California Institute of Technology9, Carnegie Institution for Science10, University of Hawaii at Manoa11, American Museum of Natural History12, University of Toronto13, Tel Aviv University14, University of Tokyo15
TL;DR: The luminosity of the progenitor system (especially the companion star) is 10–100 times fainter than previous limits on other type Ia supernova progenitors systems, allowing us to rule out luminous red giants and almost all helium stars as the mass-donating companion to the exploding white dwarf.
Abstract: 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.
382 citations
TL;DR: In this article, a new non-detection limit of the nearby SN Ia 2011fe, obtained what appears to be just 4 hours after the explosion, was presented, allowing us to directly constrain the initial primary radius, R_p Coupled with the nondetection of a quiescent X-ray counterpart and the inferred synthesized Ni mass, we show that R_ p 10,000 gm cm^{-3}, and that the effective temperature must be less than a few x 10^5 K.
Abstract: While a white dwarf is, from a theoretical perspective, the most plausible primary star in 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 what appears to be just 4 hours after explosion, allowing us to directly constrain the initial primary radius, R_p Coupled with the non-detection of a quiescent X-ray counterpart and the inferred synthesized Ni mass, we show that R_p 10,000 gm cm^{-3}, and that the effective temperature must be less than a few x 10^5 K This rules out hydrogen burning main sequence stars and giants Constructing the helium-burning main sequence and carbon-burning main sequence, we find 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 <~ 01 R_sun, excluding Roche-Lobe overflowing red giant and main-sequence companions to high significance
232 citations
Weizmann Institute of Science1, California Institute of Technology2, University of California, Berkeley3, University of Oxford4, Lawrence Berkeley National Laboratory5, Tel Aviv University6, Las Cumbres Observatory Global Telescope Network7, University of California, Santa Barbara8, Liverpool John Moores University9, Max Planck Society10, Scuola Normale Superiore di Pisa11, Pennsylvania State University12, Goddard Space Flight Center13, University of Toronto14
TL;DR: In this paper, the bolometric luminosity of a supernova explosion in the nearby galaxy M51 (the Whirlpool Galaxy) was calculated using multi-color ultraviolet through infrared photometry.
Abstract: 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 (~10^(13) cm) would be highly inconsistent with constraints from our post-explosion spectra.
224 citations
University of Leicester1, University of Warwick2, Goddard Space Flight Center3, University of Maryland, Baltimore County4, Liverpool John Moores University5, DSM6, University College London7, INAF8, Niels Bohr Institute9, Stockholm University10, Centre national de la recherche scientifique11, Janssen Pharmaceutica12, Space Telescope Science Institute13, Pennsylvania State University14, University of Notre Dame15, Spanish National Research Council16, Universities Space Research Association17, Marshall Space Flight Center18, University of Iceland19, University of Amsterdam20, VU University Amsterdam21, Max Planck Society22, Lawrence Berkeley National Laboratory23, Ohio State University24, University of California, Santa Cruz25
TL;DR: In this article, the authors report the discovery of the nearby long, soft gamma-ray burst GRB 100316D, and the subsequent unveiling of its low-redshift host galaxy and associated supernova.
Abstract: We report the Swift discovery of the nearby long, soft gamma-ray burst GRB 100316D, and the subsequent unveiling of its low-redshift host galaxy and associated supernova. We derive the redshift of the event to be z = 0.0591 +/- 0.0001 and provide accurate astrometry for the gamma-ray burst (GRB) supernova (SN). We study the extremely unusual prompt emission with time-resolved gamma-ray to X-ray spectroscopy and find that the spectrum is best modelled with a thermal component in addition to a synchrotron emission component with a low peak energy. The X-ray light curve has a remarkably shallow decay out to at least 800 s. The host is a bright, blue galaxy with a highly disturbed morphology and we use Gemini-South, Very Large Telescope and Hubble Space Telescope observations to measure some of the basic host galaxy properties. We compare and contrast the X-ray emission and host galaxy of GRB 100316D to a subsample of GRB-SNe. GRB 100316D is unlike the majority of GRB-SNe in its X-ray evolution, but resembles rather GRB 060218, and we find that these two events have remarkably similar high energy prompt emission properties. Comparison of the host galaxies of GRB-SNe demonstrates, however, that there is a great diversity in the environments in which GRB-SNe can be found. GRB 100316D is an important addition to the currently sparse sample of spectroscopically confirmed GRB-SNe, from which a better understanding of long GRB progenitors and the GRB-SN connection can be gleaned.
212 citations
TL;DR: A new computer program, SYNAPPS, for forward-modeling of supernova (SN) spectroscopy data sets, a spectrum fitter embedding a highly parameterized synthetic SN spectrum calculation within a parallel asynchronous optimizer.
Abstract: We introduce a new computer program, SYNAPPS, for forward-modeling of supernova (SN) spectroscopy data sets. SYNAPPS is a spectrum fitter embedding a highly parameterized synthetic SN spectrum calculation within a parallel asynchronous optimizer. This open-source code is primarily aimed at the problem of systematically interpreting large sets of SN spectroscopy data. While SYNAPPS should be useful to current SN spectroscopy efforts like the Nearby Supernova Factory, Lick Observatory Supernova Search, Palomar Transient Factory, Harvard Center for Astrophysics SN program, and so on, it could also benefit future similar efforts connected to the Dark Energy Survey, Panoramic Survey Telescope and Rapid Response System, or the Large Synoptic Survey Telescope. Smaller programs are also potential users. SYNAPPS illustrates the potential for data-driven discovery enabled by high-performance computing, where complex physical systems are directly constrained by large information-rich sets of scientific observations. Here, we discuss the motivation of our approach, outline the structure of the code, present some example calculations, and describe a few enhancements in terms of physics modeling, optimization, and computing that we will be pursuing for the future.
182 citations
TL;DR: In this article, a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy) and rapidly confirmed it to be a Type II supernova.
Abstract: On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We discovered this event using small telescopes equipped with CCD cameras, as well as by the Palomar Transient Factory (PTF) survey, and rapidly confirmed it to be a Type II supernova. Our early light curve and spectroscopy indicates that PTF11eon resulted from the explosion of a relatively compact progenitor star as evidenced by the rapid shock-breakout cooling seen in the light curve, the relatively low temperature in early-time spectra and the prompt appearance of low-ionization spectral features. The spectra of PTF11eon are dominated by H lines out to day 10 after explosion, but initial signs of He appear to be present. Assuming that He lines continue to develop in the near future, this SN is likely a member of the cIIb (compact IIb; Chevalier and Soderberg 2010) 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 (~10^13 cm) would be highly inconsistent with constraints from our post-explosion photometric and spectroscopic data.
181 citations
California Institute of Technology1, University of Oxford2, Weizmann Institute of Science3, Las Cumbres Observatory Global Telescope Network4, Lawrence Berkeley National Laboratory5, Carnegie Institution for Science6, Max Planck Society7, Goddard Space Flight Center8, Columbia University9, Johns Hopkins University10, Yonsei University11, University of California, Los Angeles12
TL;DR: In this paper, GALEX ultraviolet (UV) and optical integrated photometry of the hosts of 17 luminous supernovae (LSNe), by appearing in low-SFR hosts, are potential tests for theories of the initial mass function that limit the maximum mass of a star based on the SFR.
Abstract: We use GALEX ultraviolet (UV) and optical integrated photometry of the hosts of 17 luminous supernovae (LSNe, having peak M_V 100 M_☉), by appearing in low-SFR hosts, are potential tests for theories of the initial mass function that limit the maximum mass of a star based on the SFR.
172 citations
TL;DR: In this paper, the authors employed 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 supernova intrinsic luminosity and determine a dust reddening law.
Abstract: 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, R v = 2.8 ± 0.3. This agrees with the Milky Way value, in contrast to the low R v values 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.
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TL;DR: BigBOSS as discussed by the authors is a ground-based dark energy experiment to study baryon acoustic oscillations and the growth of structure with a wide-area galaxy and quasar redshift survey over 14,000 square degrees.
Abstract: BigBOSS is a Stage IV ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the growth of structure with a wide-area galaxy and quasar redshift survey over 14,000 square degrees. It has been conditionally accepted by NOAO in response to a call for major new instrumentation and a high-impact science program for the 4-m Mayall telescope at Kitt Peak. The BigBOSS instrument is a robotically-actuated, fiber-fed spectrograph capable of taking 5000 simultaneous spectra over a wavelength range from 340 nm to 1060 nm, with a resolution R = 3000-4800.
Using data from imaging surveys that are already underway, spectroscopic targets are selected that trace the underlying dark matter distribution. In particular, targets include luminous red galaxies (LRGs) up to z = 1.0, extending the BOSS LRG survey in both redshift and survey area. To probe the universe out to even higher redshift, BigBOSS will target bright [OII] emission line galaxies (ELGs) up to z = 1.7. In total, 20 million galaxy redshifts are obtained to measure the BAO feature, trace the matter power spectrum at smaller scales, and detect redshift space distortions. BigBOSS will provide additional constraints on early dark energy and on the curvature of the universe by measuring the Ly-alpha forest in the spectra of over 600,000 2.2 < z < 3.5 quasars.
BigBOSS galaxy BAO measurements combined with an analysis of the broadband power, including the Ly-alpha forest in BigBOSS quasar spectra, achieves a FOM of 395 with Planck plus Stage III priors. This FOM is based on conservative assumptions for the analysis of broad band power (kmax = 0.15), and could grow to over 600 if current work allows us to push the analysis to higher wave numbers (kmax = 0.3). BigBOSS will also place constraints on theories of modified gravity and inflation, and will measure the sum of neutrino masses to 0.024 eV accuracy.
TL;DR: The inner workings of a framework, based on machine-learning algorithms, that captures expert training and ground-truth knowledge about the variable and transient sky to automate the process of discovery on image differences, and the generation of preliminary science-type classifications of discovered sources are presented.
Abstract: The rate of image acquisition in modern synoptic imaging surveys has already begun to outpace the feasibility of keeping astronomers in the real-time discovery and classification loop. Here we present the inner workings of a framework, based on machine-learning algorithms, that captures expert training and ground-truth knowledge about the variable and transient sky to automate 1) the process of discovery on image differences and, 2) the generation of preliminary science-type classifications of discovered sources. Since follow-up resources for extracting novel science from fast-changing transients are precious, self-calibrating classification probabilities must be couched in terms of efficiencies for discovery and purity of the samples generated. We estimate the purity and efficiency in identifying real sources with a two-epoch image-difference discovery algorithm for the Palomar Transient Factory (PTF) survey. Once given a source discovery, using machine-learned classification trained on PTF data, we distinguish between transients and variable stars with a 3.8% overall error rate (with 1.7% errors for imaging within the Sloan Digital Sky Survey footprint). At >96% classification efficiency, the samples achieve 90% purity. Initial classifications are shown to rely primarily on context-based features, determined from the data itself and external archival databases. In the ~one year since autonomous operations, this discovery and classification framework has led to several significant science results, from outbursting young stars to subluminous Type IIP supernovae to candidate tidal disruption events. We discuss future directions of this approach, including the possible roles of crowdsourcing and the scalability of machine learning to future surveys such a the Large Synoptical Survey Telescope (LSST).
TL;DR: In this article, the authors present the 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.
Abstract: On 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 dM/dt<10^-8 (w/100 km/s) [M_solar/yr] 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 (decade or longer) in order to more meaningfully probe the circumstellar matter of Ia supernovae.
Liverpool John Moores University1, University of Ferrara2, University of Warwick3, University of Leicester4, INAF5, Space Telescope Science Institute6, University of Notre Dame7, University of Ljubljana8, Spanish National Research Council9, University of California, Berkeley10, Max Planck Society11, Lawrence Berkeley National Laboratory12, ASTRON13, University of Amsterdam14, University of California, Santa Cruz15
TL;DR: 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.
Abstract: 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 M{sub V} = -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{sub 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{sub Ni}more » {approx} 0.1 M{sub sun}, ejected M{sub ej} {approx} 2.2 M{sub sun}, and has an explosion energy of E{sub k} {approx} 1.4 x 10{sup 52} erg. 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.« less
TL;DR: In this paper, 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) were presented.
Abstract: 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 ≳ 4 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 H_(2)O, 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.
TL;DR: In this article, rotation periods for 40 late-K to mid-M star members of the nearby, rich, intermediate-age (600 Myr) open cluster Praesepe were derived from 200 observations taken by the Palomar Transient Factory of four cluster fields from 2010 February to May.
Abstract: 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_☉. 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.
TL;DR: In this paper, the Palomar Transient Factory (PTF) provides multiple epoch imaging for a large fraction of the sky, and the calibration process utilizes SDSS r~16 mag point source objects as photometric standards.
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).
TL;DR: In this article, the authors presented convincing evidence of unburned carbon at photospheric velocities in new observations of five Type Ia supernovae (SNe Ia) obtained by the Nearby Supernova Factory.
Abstract: 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 {lambda}6580 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{sup -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{sup +10}{sub -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-positivemore » 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 {lambda}6580 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.« less
Weizmann Institute of Science1, California Institute of Technology2, Lawrence Berkeley National Laboratory3, University of California, Berkeley4, Scuola Normale Superiore di Pisa5, University of Oxford6, Las Cumbres Observatory Global Telescope Network7, University of California, Santa Barbara8, Max Planck Society9, National Radio Astronomy Observatory10, Liverpool John Moores University11, University of Michigan12, Australian National University13, University of Toronto14, Pennsylvania State University15, Goddard Space Flight Center16
TL;DR: The Palomar Transient Factory (PTF) as discussed by the authors is an optical wide field variability survey carried out using a camera with a 7.8 deg^2 field of view mounted on the 48 inch Oschin Schmidt telescope at Palomars Observatory.
Abstract: The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 deg^2 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.
Liverpool John Moores University1, University of Ferrara2, Brera Astronomical Observatory3, University of Warwick4, University of Leicester5, Marshall Space Flight Center6, University of Cambridge7, Spanish National Research Council8, University of Copenhagen9, Seoul National University10, University of Amsterdam11, Indian Institute of Astrophysics12, University of Valencia13, University of Sheffield14, University of Stuttgart15, Ames Research Center16, Paris Diderot University17, Russian Academy of Sciences18, Space Telescope Science Institute19, University of Notre Dame20, University of Ljubljana21, University of North Carolina at Chapel Hill22, Academia Sinica Institute of Astronomy and Astrophysics23, University of Bristol24, Academy of Sciences of Uzbekistan25, Korea Astronomy and Space Science Institute26, University of California, Santa Cruz27, Max Planck Society28, Lawrence Berkeley National Laboratory29, Scuola Normale Superiore di Pisa30, Arizona State University31, Carnegie Institution for Science32, James Cook University33, ASTRON34, Las Cumbres Observatory Global Telescope Network35, Queen Mary University of London36, National Central University37, Moscow State University38, Queen's University Belfast39
TL;DR: In this paper, 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, were presented.
Abstract: 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 - t(o) > 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.
University of California, Irvine1, University of California, Los Angeles2, University of California, Berkeley3, Jet Propulsion Laboratory4, Brigham Young University5, University of California, Santa Barbara6, Lawrence Berkeley National Laboratory7, University of Texas at Austin8, University of California, Santa Cruz9, Centre national de la recherche scientifique10, SLAC National Accelerator Laboratory11, Pennsylvania State University12, University of Alabama13, University of California, San Diego14, Seoul National University15
TL;DR: In this paper, the authors used the Kast Spectrograph at the Lick 3 m telescope and 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 to determine the black hole mass in Zw 229-015 from Hβ reverberation mapping.
Abstract: 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 ☉ 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.
TL;DR: In this paper, the authors used the Kast Spectrograph at the Lick 3m telescope during the dark runs from June through December 2010, obtaining 54 spectroscopic observations in total.
Abstract: 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 H-beta reverberation mapping, we have carried out nightly observations with the Kast Spectrograph at the Lick 3m telescope during the dark runs from June through December 2010, 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 0.9m 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 2 change in broad H-beta flux. From cross-correlation measurements, we find that the H-beta 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 H-alpha and H-gamma and find an upper limit to the H-delta lag. Combining the H-beta lag measurement with a broad H-beta width of sigma = 1590+/-47 km/s measured from the root-mean-square variability spectrum, we obtain a virial estimate of M_BH = 1.00(-0.24,+0.19)*10^7 solar masses 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.
California Institute of Technology1, Lawrence Berkeley National Laboratory2, University of California, Berkeley3, Las Cumbres Observatory Global Telescope Network4, INAF5, Liverpool John Moores University6, Australian National University7, Pennsylvania State University8, Goddard Space Flight Center9
TL;DR: The Palomar Transient Factory (PTF) as mentioned in this paper is an optical wide field variability survey carried out using a camera with a 7.8 square degree field of view mounted on the 48-in Oschin Schmidt telescope at Palomars Observatory.
Abstract: The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 square degree field of view mounted on the 48-in 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 gamma-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.
TL;DR: In this article, the authors present the optical photometry and spectroscopy gathered for SN 2000cb, which is clearly not a standard SNII and yet is not a SN 1987A analogue.
Abstract: 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 56 Ni. Adding a similar object to the sample, SN2005ci, we derive a rate of ∼2 per cent of the core-collapse rate for this loosely defined class of BSG explosions.
TL;DR: In this article, the Palomar Transient Factory (PTF) detected an optical outburst (dubbed PTF10nvg) associated with the previously unstudied flat or rising spectrum infrared source IRAS 20496+4354.
Abstract: During a synoptic survey of the North American Nebula region, the Palomar Transient Factory (PTF) detected an optical outburst (dubbed PTF10nvg) associated with the previously unstudied flat or rising spectrum infrared source IRAS 20496+4354 The PTF R-band light curve reveals that PTF10nvg brightened by more than 5 mag during the current outburst, rising to a peak magnitude of R_(PTF) ≈ 135 in 2010 September Follow-up observations indicate that PTF10nvg has undergone a similar ~5 mag brightening in the K band and possesses a rich emission-line spectrum, including numerous lines commonly assumed to trace mass accretion and outflows Many of these lines are blueshifted by ~175 km s^(–1) from the North American Nebula's rest velocity, suggesting that PTF10nvg is driving an outflow Optical spectra of PTF10nvg show several TiO/VO band heads fully in emission, indicating the presence of an unusual amount of dense (>10^(10) cm^(–3)), warm (1500-4000 K) circumstellar material Near-infrared spectra of PTF10nvg appear quite similar to a spectrum of McNeil's Nebula/V1647 Ori, a young star which has undergone several brightenings in recent decades, and 06297+1021W, a Class I protostar with a similarly reached near-infrared emission line spectrum While further monitoring is required to fully understand this event, we conclude that the brightening of PTF10nvg is indicative of enhanced accretion and outflow in this Class-I-type protostellar object, similar to the behavior of V1647 Ori in 2004-2005
TL;DR: In this article, the authors presented extensive photometric and spectroscopic observations of PTF1 J071912.13+485834.0, an outbursting AM CVn system discovered by the Palomar Transient Factory (PTF).
Abstract: 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.
University of Oxford1, California Institute of Technology2, Lawrence Berkeley National Laboratory3, University of California, Santa Barbara4, Las Cumbres Observatory Global Telescope Network5, Weizmann Institute of Science6, INAF7, Max Planck Society8, Kavli Institute for Theoretical Physics9, University of California, Berkeley10, University of Toronto11
TL;DR: 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 sub-lightweight SN1991bg-like SNe, but it has several unusual features which make it stand out from this population as mentioned in this paper.
Abstract: 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 ^(56)Ni mass is small (0.019 ± 0.003 M_☉), as is the estimated ejecta mass of 0.36 M_☉. 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.
TL;DR: In this article, ultraviolet spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) were obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope.
Abstract: We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This dataset provides unique spectral time series down to 2000 Angstrom. Significant diversity is seen in the near maximum-light spectra (~ 2000--3500 Angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminosities measured in uvw1/F250W are found to correlate with the B-band light-curve shape parameter dm15(B), but with much larger scatter relative to the correlation in the broad-band B band (e.g., ~0.4 mag versus ~0.2 mag for those with 0.8 3 sigma), being brighter than normal SNe Ia such as SN 2005cf by ~0.9 mag and ~2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.
California Institute of Technology1, Weizmann Institute of Science2, Lawrence Berkeley National Laboratory3, Pennsylvania State University4, University of California, Berkeley5, University of Toronto6, National Radio Astronomy Observatory7, Goddard Space Flight Center8, University of Oxford9, University of California, Santa Barbara10, Princeton University11
TL;DR: The discovery of PTF 10fqs, a transient in the luminosity gap between novae and supernovae, was reported in this paper, where the explosion signature (the light curve and spectra) is overall similar to that of M85 OT2006-1, SN 2008S, and NGC 300 OT.
Abstract: The Palomar Transient Factory (PTF) is systematically charting the optical transient and variable sky. A primary
science driver of PTF is building a complete inventory of transients in the local universe (distance less than 200 Mpc). Here, we report the discovery of PTF 10fqs, a transient in the luminosity “gap” between novae and supernovae. Located on a spiral arm of Messier 99, PTF 10fqs has a peak luminosity of M_r = −12.3, red color (g − r = 1.0), and is slowly evolving (decayed by 1 mag in 68 days). It has a spectrum dominated by intermediate-width Hα
(≈930 km s^(−1)) and narrow calcium emission lines. The explosion signature (the light curve and spectra) is overall
similar to that of M85 OT2006-1, SN 2008S, and NGC 300 OT. The origin of these events is shrouded in mystery
and controversy (and in some cases, in dust). PTF 10fqs shows some evidence of a broad feature (around 8600 A)
that may suggest very large velocities (≈10,000 km s^(−1)) in this explosion. Ongoing surveys can be expected to find
a few such events per year. Sensitive spectroscopy, infrared monitoring, and statistics (e.g., disk versus bulge) will eventually make it possible for astronomers to unravel the nature of these mysterious explosions.