Showing papers by "Peter Nugent published in 2019"
University of Washington1, California Institute of Technology2, Stockholm University3, University of Maryland, College Park4, Humboldt University of Berlin5, Goddard Space Flight Center6, National Central University7, Weizmann Institute of Science8, Macau University of Science and Technology9, Tel Aviv University10, University of California, Santa Barbara11, University of Michigan12, Northwestern University13, Adler Planetarium14, Lawrence Berkeley National Laboratory15, University of California, Berkeley16, Soka University of America17, Centre national de la recherche scientifique18, Radboud University Nijmegen19, University of Wisconsin–Milwaukee20, Los Alamos National Laboratory21
TL;DR: The Zwicky Transient Facility (ZTF) as mentioned in this paper is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope, which provides a 47 deg^2 field of view and 8 s readout time, yielding more than an order of magnitude improvement in survey speed relative to its predecessor survey.
Abstract: The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope. A custom-built wide-field camera provides a 47 deg^2 field of view and 8 s readout time, yielding more than an order of magnitude improvement in survey speed relative to its predecessor survey, the Palomar Transient Factory. We describe the design and implementation of the camera and observing system. The ZTF data system at the Infrared Processing and Analysis Center provides near-real-time reduction to identify moving and varying objects. We outline the analysis pipelines, data products, and associated archive. Finally, we present on-sky performance analysis and first scientific results from commissioning and the early survey. ZTF's public alert stream will serve as a useful precursor for that of the Large Synoptic Survey Telescope.
1,009 citations
TL;DR: The DESI Legacy Imaging Surveys (http://legacysurvey.org/) as mentioned in this paper is a combination of three public projects (the Dark Energy Camera Legacy Survey, the Beijing-Arizona Sky Survey, and the Mayall z-band Legacy Survey) that will jointly image ≈14,000 deg2 of the extragalactic sky visible from the northern hemisphere in three optical bands (g, r, and z) using telescopes at the Kitt Peak National Observatory and the Cerro Tololo Inter-American Observatory.
Abstract: The DESI Legacy Imaging Surveys (http://legacysurvey.org/) are a combination of three public projects (the Dark Energy Camera Legacy Survey, the Beijing–Arizona Sky Survey, and the Mayall z-band Legacy Survey) that will jointly image ≈14,000 deg2 of the extragalactic sky visible from the northern hemisphere in three optical bands (g, r, and z) using telescopes at the Kitt Peak National Observatory and the Cerro Tololo Inter-American Observatory. The combined survey footprint is split into two contiguous areas by the Galactic plane. The optical imaging is conducted using a unique strategy of dynamically adjusting the exposure times and pointing selection during observing that results in a survey of nearly uniform depth. In addition to calibrated images, the project is delivering a catalog, constructed by using a probabilistic inference-based approach to estimate source shapes and brightnesses. The catalog includes photometry from the grz optical bands and from four mid-infrared bands (at 3.4, 4.6, 12, and 22 μm) observed by the Wide-field Infrared Survey Explorer satellite during its full operational lifetime. The project plans two public data releases each year. All the software used to generate the catalogs is also released with the data. This paper provides an overview of the Legacy Surveys project.
517 citations
TL;DR: The Zwicky Transient Facility (ZTF) as discussed by the authors is a new time domain survey employing a dedicated camera on the Palomar 48-inch Schmidt telescope with a 47 deg$^2$ field of view and 8 second readout time.
Abstract: The Zwicky Transient Facility (ZTF), a public-private enterprise, is a new time domain survey employing a dedicated camera on the Palomar 48-inch Schmidt telescope with a 47 deg$^2$ field of view and 8 second readout time. It is well positioned in the development of time domain astronomy, offering operations at 10% of the scale and style of the Large Synoptic Survey Telescope (LSST) with a single 1-m class survey telescope. The public surveys will cover the observable northern sky every three nights in g and r filters and the visible Galactic plane every night in g and r. Alerts generated by these surveys are sent in real time to brokers. A consortium of universities which provided funding ("partnership") are undertaking several boutique surveys. The combination of these surveys producing one million alerts per night allows for exploration of transient and variable astrophysical phenomena brighter than r $\sim$ 20.5 on timescales of minutes to years. We describe the primary science objectives driving ZTF including the physics of supernovae and relativistic explosions, multi-messenger astrophysics, supernova cosmology, active galactic nuclei and tidal disruption events, stellar variability, and Solar System objects.
501 citations
California Institute of Technology1, University of Washington2, Stockholm University3, University of Maryland, College Park4, Auburn University5, University of Wisconsin–Milwaukee6, Goddard Space Flight Center7, National Central University8, University of California, Santa Barbara9, University of Michigan10, Northwestern University11, Adler Planetarium12, University of California, Berkeley13, Lawrence Berkeley National Laboratory14, Weizmann Institute of Science15, Radboud University Nijmegen16, Humboldt University of Berlin17, Macau University of Science and Technology18, Tel Aviv University19, Soka University of America20, Centre national de la recherche scientifique21, Los Alamos National Laboratory22
TL;DR: The Zwicky Transient Facility (ZTF) as mentioned in this paper is a new time-domain survey employing a dedicated camera on the Palomar 48-inch Schmidt telescope with a 47 deg^2 field of view and an 8 second readout time.
Abstract: The Zwicky Transient Facility (ZTF), a public–private enterprise, is a new time-domain survey employing a dedicated camera on the Palomar 48-inch Schmidt telescope with a 47 deg^2 field of view and an 8 second readout time. It is well positioned in the development of time-domain astronomy, offering operations at 10% of the scale and style of the Large Synoptic Survey Telescope (LSST) with a single 1-m class survey telescope. The public surveys will cover the observable northern sky every three nights in g and r filters and the visible Galactic plane every night in g and r. Alerts generated by these surveys are sent in real time to brokers. A consortium of universities that provided funding ("partnership") are undertaking several boutique surveys. The combination of these surveys producing one million alerts per night allows for exploration of transient and variable astrophysical phenomena brighter than r ~ 20.5 on timescales of minutes to years. We describe the primary science objectives driving ZTF, including the physics of supernovae and relativistic explosions, multi-messenger astrophysics, supernova cosmology, active galactic nuclei, and tidal disruption events, stellar variability, and solar system objects.
280 citations
University of Portsmouth1, University of Pennsylvania2, University of Queensland3, Australian National University4, African Institute for Mathematical Sciences5, University of Chicago6, Lawrence Berkeley National Laboratory7, University of Southampton8, Fermilab9, Korea Astronomy and Space Science Institute10, University College London11, Texas A&M University12, Stanford University13, University of Illinois at Urbana–Champaign14, Spanish National Research Council15, California Institute of Technology16, University of Arizona17, University of Michigan18, University of California, Berkeley19, University of California, Santa Cruz20, University of Pittsburgh21, Autonomous University of Madrid22, Swinburne University of Technology23, University of Lisbon24, ETH Zurich25, Ohio State University26, Max Planck Society27, Ludwig Maximilian University of Munich28, Harvard University29, University of Namibia30, Macquarie University31, University of Sydney32, University of São Paulo33, Academia Sinica34, National Institutes of Natural Sciences, Japan35, University of Sussex36, Brandeis University37, State University of Campinas38, Oak Ridge National Laboratory39, Carnegie Institution for Science40, Argonne National Laboratory41
TL;DR: In this paper, the authors presented an improved measurement of the Hubble constant using the inverse distance ladder method, which added the information from 207 Type Ia supernovae (SNe Ia) from the DES at redshift 0.018
Abstract: We present an improved measurement of the Hubble constant (H0) using the 'inverse distance ladder' method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) at redshift 0.018
199 citations
TL;DR: In this article, an integer linear programming approach is proposed for scheduling the observations of time-domain imaging surveys, assigning targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes.
Abstract: We present a novel algorithm for scheduling the observations of time-domain imaging surveys. Our integer linear programming approach optimizes an observing plan for an entire night by assigning targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes. A subsequent optimization step minimizes slew times between each observation. Our optimization metric self-consistently weights contributions from time-varying airmass, seeing, and sky brightness to maximize the transient discovery rate. We describe the implementation of this algorithm on the surveys of the Zwicky Transient Facility and present its on-sky performance.
170 citations
TL;DR: In this paper, the first cosmological parameter constraints using measurements of type Ia supernovae (SNe Ia) from the Dark Energy Survey Supernova Program (DES-SN) were presented.
Abstract: We present the first cosmological parameter constraints using measurements of type Ia supernovae (SNe Ia) from the Dark Energy Survey Supernova Program (DES-SN). The analysis uses a subsample of 207 spectroscopically confirmed SNe Ia from the first three years of DES-SN, combined with a low-redshift sample of 122 SNe from the literature. Our "DES-SN3YR" result from these 329 SNe Ia is based on a series of companion analyses and improvements covering SN Ia discovery, spectroscopic selection, photometry, calibration, distance bias corrections, and evaluation of systematic uncertainties. For a flat ΛCDM model we find a matter density ${{\rm{\Omega }}}_{{\rm{m}}}=0.331\pm 0.038$. For a flat wCDM model, and combining our SN Ia constraints with those from the cosmic microwave background (CMB), we find a dark energy equation of state $w=-0.978\pm 0.059$, and ${{\rm{\Omega }}}_{{\rm{m}}}=0.321\pm 0.018$. For a flat w 0 w a CDM model, and combining probes from SN Ia, CMB and baryon acoustic oscillations, we find ${w}_{0}=-0.885\pm 0.114$ and ${w}_{a}=-0.387\,\pm \,0.430$. These results are in agreement with a cosmological constant and with previous constraints using SNe Ia (Pantheon, JLA).
157 citations
TL;DR: Polin et al. as mentioned in this paper presented a numerical parameter survey of sub-Chandrasekhar mass white dwarf (WD) explosions and identified a subclass of observed supernovae that are consistent with these models.
Abstract: Author(s): Polin, A; Nugent, P; Kasen, D | Abstract: We present a numerical parameter survey of sub-Chandrasekhar mass white dwarf (WD) explosions. Carbon-oxygen WDs accreting a helium shell have the potential to explode in the sub-Chandrasekhar mass regime. Previous studies have shown how the ignition of a helium shell can either directly ignite the WD at the core-shell interface or propagate a shock wave into the the core causing a central ignition. We examine the explosions of WDs from 0.6 to 1.2 M o with helium shells of 0.01, 0.05, and 0.08 M o . Distinct observational signatures of sub-Chandrasekhar mass WD explosions are predicted for two categories of shell size. Thicker-shell models show an early time flux excess, which is caused by the presence of radioactive material in the ashes of the helium shell, and red colors due to these ashes creating significant line blanketing in the UV through the blue portion of the spectrum. Thin shell models reproduce several typical Type Ia supernova signatures. We identify a relationship between Si ii velocity and luminosity that, for the first time, identifies a subclass of observed supernovae that are consistent with these models. This subclass is further delineated by the absence of carbon in their atmospheres. We suggest that the proposed difference in the ratio of selective to total extinction between the high velocity and normal velocity Type Ia supernovae is not due to differences in the properties of the dust around these events, but is rather an artifact of applying a single extinction correction to two intrinsically different populations of supernovae.
124 citations
University of Pennsylvania1, University of Chicago2, University of Queensland3, Lawrence Berkeley National Laboratory4, Australian National University5, University of Portsmouth6, University of Southampton7, University of Copenhagen8, Korea Astronomy and Space Science Institute9, Harvard University10, African Institute for Mathematical Sciences11, Texas A&M University12, Pontifical Catholic University of Chile13, University of California, Berkeley14, University of California, Santa Cruz15, University of Pittsburgh16, Swinburne University of Technology17, University of Namibia18, Gordon and Betty Moore Foundation19, Macquarie University20, Argonne National Laboratory21, University of Sydney22, University of Cambridge23, University of Arizona24, University of Illinois at Urbana–Champaign25, Fermilab26, Academia Sinica27, National Institutes of Natural Sciences, Japan28, Carnegie Institution for Science29, Institut d'Astrophysique de Paris30, University College London31, SLAC National Accelerator Laboratory32, Stanford University33, IFAE34, Spanish National Research Council35, Indian Institute of Technology, Hyderabad36, California Institute of Technology37, Autonomous University of Madrid38, ETH Zurich39, Ohio State University40, Max Planck Society41, Ludwig Maximilian University of Munich42, University of São Paulo43, University of Michigan44, University of Sussex45, Universidade Federal do Rio Grande do Sul46, Brandeis University47, State University of Campinas48, Oak Ridge National Laboratory49
TL;DR: In this paper, the analysis underpinning the measurement of cosmological parameters from 207 spectroscopically classified SNe Ia from the first 3 years of the DES-SN, spanning a redshift range of 0.017 < z < 0.849.
Abstract: We present the analysis underpinning the measurement of cosmological parameters from 207 spectroscopically classified SNe Ia from the first 3 years of the Dark Energy Survey Supernova Program (DES-SN), spanning a redshift range of 0.017 < z < 0.849. We combine the DES-SN sample with an external sample of 122 low-redshift (z < 0.1) SNe. Ia, resulting in a "DES-SN3YR" sample of 329 SNe Ia. Our cosmological analyses are blinded: after combining our DES-SN3YR distances with constraints from the Cosmic Microwave Background, our uncertainties in the measurement of the dark energy equation-of-state parameter, w, are 0.042. (stat) and 0.059 (stat+syst) at 68% confidence. We provide a detailed systematic uncertainty budget, which has nearly equal contributions from photometric calibration, astrophysical bias corrections, and instrumental bias corrections. We also include several new sources of systematic uncertainty. While our sample is less than one-third the size of the Pantheon sample, our constraints on w are only larger by 1.4x, showing the impact of the DES-SN. Ia light-curve quality. We find that the traditional stretch and color standardization parameters of the DES-SNe. Ia are in agreement with earlier SN. Ia samples such as Pan-STARRS1 and the Supernova Legacy Survey. However, we find smaller intrinsic scatter about the Hubble diagram (0.077 mag). Interestingly, we find no evidence for a Hubble residual step (0.007 +/- 0.018 mag) as a function of host-galaxy mass for the DES subset, in 2.4 sigma tension with previous measurements. We also present novel validation methods of our sample using simulated SNe. Ia inserted in DECam images and using large catalog-level simulations to test for biases in our analysis pipelines.
100 citations
California Institute of Technology1, Northwestern University2, Adler Planetarium3, Stockholm University4, University of California, Berkeley5, Lawrence Berkeley National Laboratory6, Radboud University Nijmegen7, University of Auvergne8, Humboldt University of Berlin9, University of Washington10, Goddard Space Flight Center11, University of Maryland, College Park12, University of California, Santa Cruz13, Kavli Institute for Theoretical Physics14, Liverpool John Moores University15, Weizmann Institute of Science16
TL;DR: In this article, the authors presented high-quality light curves of 127 SNe Ia discovered by the Zwicky Transient Facility (ZTF) in 2018, which can be used to study the shape and color evolution of the rising light curves in unprecedented detail.
Abstract: Early-time observations of Type Ia supernovae (SNe Ia) are essential to constrain their progenitor properties. In this paper, we present high-quality light curves of 127 SNe Ia discovered by the Zwicky Transient Facility (ZTF) in 2018. We describe our method to perform forced point spread function (PSF) photometry, which can be applied to other types of extragalactic transients. With a planned cadence of six observations per night ($3g+3r$), all of the 127 SNe Ia are detected in both $g$ and $r$ band more than 10\,d (in the rest frame) prior to the epoch of $g$-band maximum light. The redshifts of these objects range from $z=0.0181$ to 0.165; the median redshift is 0.074. Among the 127 SNe, 50 are detected at least 14\,d prior to maximum light (in the rest frame), with a subset of 9 objects being detected more than 17\,d before $g$-band peak. This is the largest sample of young SNe Ia collected to date; it can be used to study the shape and color evolution of the rising light curves in unprecedented detail. We discuss six peculiar events in this sample, including one 02cx-like event ZTF18abclfee (SN\,2018crl), one Ia-CSM SN ZTF18aaykjei (SN\,2018cxk), and four objects with possible super-Chandrasekhar mass progenitors: ZTF18abhpgje (SN\,2018eul), ZTF18abdpvnd (SN\,2018dvf), ZTF18aawpcel (SN\,2018cir) and ZTF18abddmrf (SN\,2018dsx).
89 citations
University of Southampton1, University of Pittsburgh2, Korea Astronomy and Space Science Institute3, Texas A&M University4, Spanish National Research Council5, Swinburne University of Technology6, SLAC National Accelerator Laboratory7, Stanford University8, University of Chicago9, Lawrence Berkeley National Laboratory10, Australian National University11, University of Pennsylvania12, Brandeis University13, Institut d'Astrophysique de Paris14, University College London15, Fermilab16, IFAE17, Indian Institute of Technology, Hyderabad18, California Institute of Technology19, Steward Health Care System20, Autonomous University of Madrid21, University of Illinois at Urbana–Champaign22, National Center for Supercomputing Applications23, ETH Zurich24, Santa Cruz Institute for Particle Physics25, Ohio State University26, Max Planck Society27, Ludwig Maximilian University of Munich28, Harvard University29, Macquarie University30, University of São Paulo31, University of Michigan32, Catalan Institution for Research and Advanced Studies33, University of Sussex34, State University of Campinas35, Oak Ridge National Laboratory36, Institute of Cosmology and Gravitation, University of Portsmouth37
TL;DR: In this paper, the authors presented a sample of 21 hydrogen-free superluminous supernovae (SLSNe-I) and one hydrogen-rich SLSN-II detected during the five-year Dark Energy Survey (DES).
Abstract: We present a sample of 21 hydrogen-free superluminous supernovae (SLSNe-I) and one
hydrogen-rich SLSN (SLSN-II) detected during the five-year Dark Energy Survey (DES).
These SNe, located in the redshift range 0.220 < z < 1.998, represent the largest homogeneously
selected sample of SLSN events at high redshift.We present the observed g, r, i, z light
curves for these SNe,which we interpolate using Gaussian processes. The resulting light curves
are analysed to determine the luminosity function of SLSNe-I, and their evolutionary timescales.
The DES SLSN-I sample significantly broadens the distribution of SLSN-I light-curve
properties when combined with existing samples from the literature. We fit a magnetar model
to our SLSNe, and find that this model alone is unable to replicate the behaviour of many of the
bolometric light curves.We search theDES SLSN-I light curves for the presence of initial peaks
prior to the main light-curve peak. Using a shock breakout model, our Monte Carlo search finds
that 3 of our 14 eventswith pre-max data display such initial peaks.However, 10 events showno
evidence for such peaks, in some cases downto an absolutemagnitude of<−16, suggesting that
such features are not ubiquitous to all SLSN-I events. We also identify a red pre-peak feature
within the light curve of one SLSN, which is comparable to that observed within SN2018bsz.
University of Chicago1, University of Pennsylvania2, University of Queensland3, Lawrence Berkeley National Laboratory4, Australian National University5, University of Portsmouth6, University of Southampton7, University of Copenhagen8, Korea Astronomy and Space Science Institute9, Harvard University10, Pontifical Catholic University of Chile11, Space Telescope Science Institute12, University of California, Berkeley13, University of California, Santa Cruz14, Swinburne University of Technology15, University of Namibia16, Gordon and Betty Moore Foundation17, University of Sydney18, University of Cambridge19, University of Illinois at Urbana–Champaign20, Academia Sinica21, National Institutes of Natural Sciences, Japan22, Carnegie Institution for Science23, Fermilab24, Institut d'Astrophysique de Paris25, University College London26, Stanford University27, IFAE28, Spanish National Research Council29, Indian Institute of Technology, Hyderabad30, University of Arizona31, California Institute of Technology32, Autonomous University of Madrid33, University of Michigan34, ETH Zurich35, Ohio State University36, Macquarie University37, University of São Paulo38, Texas A&M University39, Brandeis University40, State University of Campinas41, Oak Ridge National Laboratory42
TL;DR: In this paper, catalogue-level simulations of Type Ia supernova (SN Ia) light curves in the DES-SN and in low-redshift samples from the Center for Astrophysics (CfA) and the Carnegie Supernova Project (CSP) were used to model biases from selection effects and light-curve analysis and to determine bias corrections for SN Ia distance moduli that are used to measure cosmological parameters.
Abstract: We describe catalogue-level simulations of Type Ia supernova (SN Ia) light curves in the Dark Energy Survey Supernova Program (DES-SN) and in low-redshift samples from the Center for Astrophysics (CfA) and the Carnegie Supernova Project (CSP). These simulations are used to model biases from selection effects and light-curve analysis and to determine bias corrections for SN Ia distance moduli that are used to measure cosmological parameters. To generate realistic light curves, the simulation uses a detailed SN Ia model, incorporates information from observations (point spread function, sky noise, zero-point), and uses summary information (e.g. detection efficiency versus signal-to-noise ratio) based on 10 000 fake SN light curves whose fluxes were overlaid on images and processed with our analysis pipelines. The quality of the simulation is illustrated by predicting distributions observed in the data. Averaging within redshift bins, we find distance modulus biases up to 0.05 mag over the redshift ranges of the low-z and DES-SN samples. For individual events, particularly those with extreme red or blue colour, distance biases can reach 0.4 mag. Therefore, accurately determining bias corrections is critical for precision measurements of cosmological parameters. Files used to make these corrections are available at https://des.ncsa.illinois.edu/releases/sn.
TL;DR: A novel algorithm for scheduling the observations of time-domain imaging surveys by assigning targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes is presented.
Abstract: We present a novel algorithm for scheduling the observations of time-domain imaging surveys. Our Integer Linear Programming approach optimizes an observing plan for an entire night by assigning targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes. A subsequent optimization step minimizes slew times between each observation. Our optimization metric self-consistently weights contributions from time-varying airmass, seeing, and sky brightness to maximize the transient discovery rate. We describe the implementation of this algorithm on the surveys of the Zwicky Transient Facility and present its on-sky performance.
TL;DR: Blagorodnova et al. as discussed by the authors presented multiwavelength observations of the TDE iPTF15af, discovered by the intermediate Palomar Transient Factory survey at redshift z = 0.07897.
Abstract: Author(s): Blagorodnova, N; Cenko, SB; Kulkarni, SR; Arcavi, I; Bloom, JS; Duggan, G; Filippenko, AV; Fremling, C; Horesh, A; Hosseinzadeh, G; Karamehmetoglu, E; Levan, A; Masci, FJ; Nugent, PE; Pasham, DR; Veilleux, S; Walters, R; Yan, L; Zheng, W | Abstract: We present multiwavelength observations of the tidal disruption event (TDE) iPTF15af, discovered by the intermediate Palomar Transient Factory survey at redshift z = 0.07897. The optical and ultraviolet (UV) light curves of the transient show a slow decay over 5 months, in agreement with previous optically discovered TDEs. It also has a comparable blackbody peak luminosity of . The inferred temperature from the optical and UV data shows a value of (3-5) ×10 4 K. The transient is not detected in X-rays up to within the first 5 months after discovery. The optical spectra exhibit two distinct broad emission lines in the He ii region, and at later times also Hα emission. Additionally, emission from [N iii] and [O iii] is detected, likely produced by the Bowen fluorescence effect. UV spectra reveal broad emission and absorption lines associated with high-ionization states of N v, C iv, Si iv, and possibly P v. These features, analogous to those of broad absorption line quasars (BAL QSOs), require an absorber with column densities cm -2 . This optically thick gas would also explain the nondetection in soft X-rays. The profile of the absorption lines with the highest column density material at the largest velocity is opposite that of BAL QSOs. We suggest that radiation pressure generated by the TDE flare at early times could have provided the initial acceleration mechanism for this gas. Spectral UV line monitoring of future TDEs could test this proposal.
California Institute of Technology1, Lawrence Berkeley National Laboratory2, University of California, Berkeley3, Kavli Institute for Theoretical Physics4, University of California, Santa Barbara5, University of Washington6, University of Maryland, College Park7, Goddard Space Flight Center8, Northwestern University9, Adler Planetarium10
TL;DR: De et al. as discussed by the authors reported ZTF 18aaqeasu (SN 2018byg/ATLAS 18pqq), a peculiar Type I supernova, consistent with being a helium-shell double-detonation.
Abstract: Author(s): De, K; Kasliwal, MM; Polin, A; Nugent, PE; Bildsten, L; Adams, SM; Bellm, EC; Blagorodnova, N; Burdge, KB; Cannella, C; Cenko, SB; Dekany, RG; Feeney, M; Hale, D; Fremling, UC; Graham, MJ; Ho, AYQ; Jencson, JE; Kulkarni, SR; Laher, RR; Masci, FJ; Miller, AA; Patterson, MT; Rebbapragada, U; Riddle, RL; Shupe, DL; Smith, RM | Abstract: The detonation of a helium shell on a white dwarf (WD) has been proposed as a possible explosion triggering mechanism for SNe Ia. Here, we report ZTF 18aaqeasu (SN 2018byg/ATLAS 18pqq), a peculiar Type I supernova, consistent with being a helium-shell double-detonation. With a rise time of ≈18 days from explosion, the transient reached a peak absolute magnitude of M R ≈ -18.2 mag, exhibiting a light curve akin to sub-luminous SN 1991bg-like SNe Ia, albeit with an unusually steep increase in brightness within a week from explosion. Spectra taken near peak light exhibit prominent Si absorption features together with an unusually red color (g - r ≈ 2 mag) arising from nearly complete line blanketing of flux blueward of 5000 . This behavior is unlike any previously observed thermonuclear transient. Nebular phase spectra taken at and after ≈30 days from peak light reveal evidence of a thermonuclear detonation event dominated by Fe-group nucleosynthesis. We show that the peculiar properties of ZTF 18aaqeasu are consistent with the detonation of a massive (≈0.15 ) helium shell on a sub-Chandrasekhar mass (≈0.75 ) WD after including mixing of ≈0.2 of material in the outer ejecta. These observations provide evidence of a likely rare class of thermonuclear supernovae arising from detonations of massive helium shells.
University of Pennsylvania1, University of Chicago2, University of Queensland3, Lawrence Berkeley National Laboratory4, University of Portsmouth5, Australian National University6, University of Southampton7, Stanford University8, Fermilab9, African Institute for Mathematical Sciences10, Texas A&M University11, Spanish National Research Council12, University of California, Santa Cruz13, University of Pittsburgh14, University of Namibia15, University of Illinois at Urbana–Champaign16, National Institutes of Natural Sciences, Japan17, Academia Sinica18, Institut d'Astrophysique de Paris19, University College London20, SLAC National Accelerator Laboratory21, IFAE22, Indian Institute of Technology, Hyderabad23, California Institute of Technology24, University of Arizona25, Autonomous University of Madrid26, University of Michigan27, ETH Zurich28, Ohio State University29, Harvard University30, Macquarie University31, University of São Paulo32, Brandeis University33, State University of Campinas34, Oak Ridge National Laboratory35
TL;DR: In this article, the authors present griz light curves of 251 SNe Ia from the first 3 years of the DES-SN spectroscopically classified sample, which are used in the cosmological parameter analysis by employing a scene modeling approach that simultaneously models a variable transient flux and temporally constant host galaxy.
Abstract: We present griz light curves of 251 SNe Ia from the first 3 years of the Dark Energy Survey Supernova Program's (DES-SN) spectroscopically classified sample. The photometric pipeline described in this paper produces the calibrated fluxes and associated uncertainties used in the cosmological parameter analysis by employing a scene modeling approach that simultaneously models a variable transient flux and temporally constant host galaxy. We inject artificial point sources onto DECam images to test the accuracy of our photometric method. Upon comparison of input and measured artificial supernova fluxes, we find that flux biases peak at 3 mmag. We require corrections to our photometric uncertainties as a function of host galaxy surface brightness at the transient location, similar to that seen by the DES Difference Imaging Pipeline used to discover transients. The public release of the light curves can be found at https://des.ncsa.illinois.edu/releases/sn.
Carnegie Institution for Science1, Florida State University2, Aarhus University3, University of Chicago4, Texas A&M University5, University of Oklahoma6, University of La Serena7, Goddard Space Flight Center8, University of Copenhagen9, Stockholm University10, European Southern Observatory11, Yale University12, National University of La Plata13, University of Pittsburgh14, University of Chile15, California Institute of Technology16, Australian National University17, Lawrence Berkeley National Laboratory18, University of California, Berkeley19, University of Hawaii20
TL;DR: The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a “Cosmology” sample of ∼100 TypeIa supernovae located in the smooth Hubble flow as mentioned in this paper.
Abstract: Author(s): Phillips, MM; Contreras, C; Hsiao, EY; Morrell, N; Burns, CR; Stritzinger, M; Ashall, C; Freedman, WL; Hoeflich, P; Persson, SE; Piro, AL; Suntzeff, NB; Uddin, SA; Anais, J; Baron, E; Busta, L; Campillay, A; Castellon, S; Corco, C; Diamond, T; Gall, C; Gonzalez, C; Holmbo, S; Krisciunas, K; Roth, M; Seron, J; Taddia, F; Torres, S; Anderson, JP; Baltay, C; Folatelli, G; Galbany, L; Goobar, A; Hadjiyska, E; Hamuy, M; Kasliwal, M; Lidman, C; Nugent, PE; Perlmutter, S; Rabinowitz, D; Ryder, SD; Schmidt, BP; Shappee, BJ; Walker, ES | Abstract: The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a “Cosmology” sample of ∼100 TypeIa supernovae located in the smooth Hubble flow (0.03lzl0.10). Light curves were also obtained of a “Physics” sample composed of 90 nearby TypeIa supernovae at z≤0.04 selected for near-infrared spectroscopic timeseries observations. The primary emphasis of the CSP-II is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. In this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. In a companion paper, the near-infrared spectroscopy component of the project is presented.
Florida State University1, Carnegie Institution for Science2, University of Texas at Austin3, Harvard University4, University of Arizona5, Aarhus University6, University of California, Davis7, European Southern Observatory8, Yale University9, University of Oklahoma10, Physical Research Laboratory11, Goddard Space Flight Center12, National University of La Plata13, University of Chicago14, Millennium Institute15, University of Chile16, University of Pittsburgh17, University of Copenhagen18, University of Lisbon19, Stockholm University20, California Institute of Technology21, Texas A&M University22, Australian National University23, University of California, Berkeley24
TL;DR: The Carnegie Supernova Project-II (CSP-II) as discussed by the authors has been used to follow-up nearby Type Ia supernova in both the optical and the near infrared (NIR) spectra.
Abstract: Shifting the focus of Type Ia supernova (SN Ia) cosmology to the near infrared (NIR) is a promising way to significantly reduce the systematic errors, as the strategy minimizes our reliance on the empirical width-luminosity relation and uncertain dust laws. Observations in the NIR are also crucial for our understanding of the origins and evolution of these events, further improving their cosmological utility. Any future experiments in the rest-frame NIR will require knowledge of the SN Ia NIR spectroscopic diversity, which is currently based on a small sample of observed spectra. Along with the accompanying paper, Phillips et al., we introduce the Carnegie Supernova Project-II (CSP-II), to follow-up nearby SNe Ia in both the optical and the NIR. In particular, this paper focuses on the CSP-II NIR spectroscopy program, describing the survey strategy, instrumental setups, data reduction, sample characteristics, and future analyses on the data set. In collaboration with the Harvard-Smithsonian Center for Astrophysics (CfA) Supernova Group, we obtained 661 NIR spectra of 157 SNe Ia. Within this sample, 451 NIR spectra of 90 SNe Ia have corresponding CSP-II follow-up light curves. Such a sample will allow detailed studies of the NIR spectroscopic properties of SNe Ia, providing a different perspective on the properties of the unburned material; the radioactive and stable nickel produced; progenitor magnetic fields; and searches for possible signatures of companion stars.
Stockholm University1, California Institute of Technology2, Tel Aviv University3, University of Maryland, College Park4, Goddard Space Flight Center5, University of California, Berkeley6, Weizmann Institute of Science7, University of California, Santa Barbara8, Las Cumbres Observatory Global Telescope Network9, Harvard University10, Lawrence Berkeley National Laboratory11, Liverpool John Moores University12, University of Tokyo13, San Diego State University14
TL;DR: In this paper, K-corrected Bgriz light curves of 34 Type Ic supernovae with broad spectral features (SNe Ic-BL) were obtained through photometry on template-subtracted images.
Abstract: We study 34 Type Ic supernovae that have broad spectral features (SNe Ic-BL). This is the only SN type found in association with long-duration gamma-ray bursts (GRBs). We obtained our photometric data with the Palomar Transient Factory (PTF) and its continuation, the intermediate PTF (iPTF). This is the first large, homogeneous sample of SNe Ic-BL from an untargeted survey. Furthermore, given the high observational cadence of iPTF, most of these SNe Ic-BL were discovered soon after explosion. We present K-corrected Bgriz light curves of these SNe, obtained through photometry on template-subtracted images. We analyzed the shape of the r-band light curves, finding a correlation between the decline parameter Δm_(15) and the rise parameter Δm_(−10). We studied the SN colors and, based on g − r, we estimated the host-galaxy extinction for each event. Peak r-band absolute magnitudes have an average of −18.6 ± 0.5 mag. We fit each r-band light curve with that of SN 1998bw (scaled and stretched) to derive the explosion epochs. We computed the bolometric light curves using bolometric corrections, r-band data, and g − r colors. Expansion velocities from Fe II were obtained by fitting spectral templates of SNe Ic. Bolometric light curves and velocities at peak were fitted using the semianalytic Arnett model to estimate ejecta mass M_(ej), explosion energy E_K and ^(56)Ni mass M(^(56)Ni) for each SN. We find average values of M_(ej) = 4 ± 3 M⊙, EK = (7 ± 6)×10^(51) erg, and M(^(56)Ni)=0.31 ± 0.16 M⊙. The parameter distributions were compared to those presented in the literature and are overall in agreement with them. We also estimated the degree of ^(56)Ni mixing using scaling relations derived from hydrodynamical models and we find that all the SNe are strongly mixed. The derived explosion parameters imply that at least 21% of the progenitors of SNe Ic-BL are compatible with massive (> 28 M⊙), possibly single stars, whereas at least 64% might come from less massive stars in close binary systems.
TL;DR: ZTF 18aaqeasu (SN 2018byg/ATLAS 18pqq) is a double-detonation Type Ia supernova with a peak absolute magnitude of 18.2 magnitude.
Abstract: The detonation of a helium shell on a white dwarf has been proposed as a possible explosion triggering mechanism for Type Ia supernovae. Here, we report ZTF 18aaqeasu (SN 2018byg/ATLAS 18pqq), a peculiar Type I supernova, consistent with being a helium-shell double-detonation. With a rise time of $\approx 18$ days from explosion, the transient reached a peak absolute magnitude of $M_R \approx -18.2$ mag, exhibiting a light curve akin to sub-luminous SN 1991bg-like Type Ia supernovae, albeit with an unusually steep increase in brightness within a week from explosion. Spectra taken near peak light exhibit prominent Si absorption features together with an unusually red color ($g-r \approx 2$ mag) arising from nearly complete line blanketing of flux blue-wards of 5000 A. This behavior is unlike any previously observed thermonuclear transient. Nebular phase spectra taken at and after $\approx 30$ days from peak light reveal evidence of a thermonuclear detonation event dominated by Fe-group nucleosynthesis. We show that the peculiar properties of ZTF 18aaqeasu are consistent with the detonation of a massive ($\approx 0.15$ M$_\odot$) helium shell on a sub-Chandrasekhar mass ($\approx 0.75$ M$_\odot$) white dwarf after including mixing of $\approx 0.2$ M$_\odot$ of material in the outer ejecta. These observations provide evidence of a likely rare class of thermonuclear supernovae arising from detonations of massive helium shells.
California Institute of Technology1, Weizmann Institute of Science2, University of California, Berkeley3, Liverpool John Moores University4, Stockholm University5, Texas Tech University6, University of Washington7, Radboud University Nijmegen8, University of Oxford9, Goddard Space Flight Center10, University of Maryland, College Park11, Universities Space Research Association12, The Racah Institute of Physics13, University of California, Santa Cruz14, University College London15, Kavli Institute for Theoretical Physics16, National Central University17, Lawrence Berkeley National Laboratory18, Harvard University19, Tsinghua University20, Tokyo Institute of Technology21
TL;DR: Ho et al. as discussed by the authors presented detailed observations of ZTF18abukavn (SN2018gep), which was discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 ± 0.1 mag hr-1) and luminous (Mg, peak = -20 mag) transient.
Abstract: Author(s): Ho, AYQ; Goldstein, DA; Schulze, S; Khatami, DK; Perley, DA; Ergon, M; Gal-Yam, A; Corsi, A; Andreoni, I; Barbarino, C; Bellm, EC; Blagorodnova, N; Bright, JS; Burns, E; Cenko, SB; Cunningham, V; De, K; Dekany, R; Dugas, A; Fender, RP; Fransson, C; Fremling, C; Goldstein, A; Graham, MJ; Hale, D; Horesh, A; Hung, T; Kasliwal, MM; M. Kuin, NP; Kulkarni, SR; Kupfer, T; Lunnan, R; Masci, FJ; Ngeow, CC; Nugent, PE; Ofek, EO; Patterson, MT; Petitpas, G; Rusholme, B; Sai, H; Sfaradi, I; Shupe, DL; Sollerman, J; Soumagnac, MT; Tachibana, Y; Taddia, F; Walters, R; Wang, X; Yao, Y; Zhang, X | Abstract: We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 ± 0.1 mag hr-1) and luminous (Mg,peak = -20 mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (Lbol ≳ 3 × 1044 erg s-1), the short rise time (trise = 3 days in g band), and the blue colors at peak (g-r ∼ -0.4) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (Teff ≳ 40,000 K) spectra of a stripped-envelope SN. A retrospective search revealed luminous (Mg ∼ Mr ≈ mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release E γ,iso l 4.9 × 10 48 erg, a limit on X-ray emission LX l 1040 erg s-1, and a limit on radio emission ν Lν ≲ 1037 erg s-1. Taken together, we find that the early (l 10 days) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 M⊙) at large radii (3 × 1014 cm) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time (g 10 days) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.
TL;DR: Goldstein et al. as discussed by the authors used the DECam observations of S190426c, the first possible NS-black hole merger detected in GWs, as part of the multi-facility follow-up by the Global Relay of Observatories Watching Transients Happen collaboration.
Abstract: Author(s): Goldstein, DA; Andreoni, I; Nugent, PE; Kasliwal, MM; Coughlin, MW; Anand, S; Bloom, JS; Martinez-Palomera, J; Zhang, K; Ahumada, T; Bagdasaryan, A; Cooke, J; De, K; Duev, DA; Fremling, UC; Gatkine, P; Graham, M; Ofek, EO; Singer, LP; Yan, L | Abstract: The discovery of a transient kilonova following the gravitational-wave (GW) event GW170817 highlighted the critical need for coordinated rapid and wide-field observations, inference, and follow-up across the electromagnetic spectrum. In the southern hemisphere, the Dark Energy Camera (DECam) on the Blanco 4 m telescope is well suited to this task, as it is able to cover wide fields quickly while still achieving the depths required to find kilonovae like the one accompanying GW170817 to ∼500 Mpc, the binary neutron star (NS) horizon distance for current generation of LIGO/Virgo collaboration (LVC) interferometers. Here, as part of the multi-facility follow-up by the Global Relay of Observatories Watching Transients Happen collaboration, we describe the observations and automated data movement, data reduction, candidate discovery, and vetting pipeline of our target-of-opportunity DECam observations of S190426c, the first possible NS-black hole merger detected in GWs. Starting 7.5 hr after S190426c, over 11.28 hr of observations, we imaged an area of 525 deg2 (r band) and 437 deg2 (z band); this was 16.3% of the total original localization probability, and nearly all of the probability visible from the southern hemisphere. The machine-learning-based pipeline was optimized for fast turnaround, delivering transients for human vetting within 17 minutes, on average, of shutter closure. We reported nine promising counterpart candidates 2.5 hr before the end of our observations. One hour after our data-taking ended (roughly 20 hr after the announcement of S190426c), LVC released a refined skymap that reduced the probability coverage of our observations to 8.0%, demonstrating a critical need for localization updates on shorter (∼hour) timescales. Our observations yielded no detection of a bona fide counterpart to m z = 21.7 and m r = 22.2 at the 5σ level of significance, consistent with the refined LVC positioning. We view these observations and rapid inferencing as an important real-world test for this novel end-to-end wide-field pipeline.
University of Southampton1, Institute of Cosmology and Gravitation, University of Portsmouth2, Lawrence Berkeley National Laboratory3, University of California, Berkeley4, University of California, Santa Cruz5, Goddard Space Flight Center6, University of Maryland, College Park7, California Institute of Technology8, Queen's University Belfast9, Weizmann Institute of Science10, Tel Aviv University11, San Diego State University12
TL;DR: Frohmaier et al. as mentioned in this paper measured the volumetric rate of normal type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory (PTF).
Abstract: Author(s): Frohmaier, C; Sullivan, M; Nugent, PE; Smith, M; Dimitriadis, G; Bloom, JS; Cenko, SB; Kasliwal, MM; Kulkarni, SR; Maguire, K; Ofek, EO; Poznanski, D; Quimb, RM | Abstract: We present the volumetric rate of normal type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory (PTF). Using strict data-quality cuts, and considering only periods when the PTF maintained a regular cadence, PTF discovered 90 SNe Ia at z 0.09 in a well-controlled sample over three years of operation (2010-2012). We use this to calculate the volumetric rate of SN Ia events by comparing this sample to simulations of hundreds of millions of SN Ia light curves produced in statistically representative realizations of the PTF survey. This quantifies the recovery efficiency of each PTF SN Ia event, and thus the relative weighting of each event. From this, the volumetric SN Ia rate was found to be rv = 2.43 ± 0.29 (stat)+0.33 -0.19(sys) × 10-5 SNe yr-1 Mpc-3 h3 70. This represents the most precise local measurement of the SNIa rate.We fit a simple SNIa delay-time distributionmodel,αt-β , to our PTF rate measurement combined with a literature sample of rate measurements from surveys at higher redshifts. We find β∼ 1, consistent with a progenitor channel governed by the gravitational inspiral of binary white dwarfs.
TL;DR: Goldstein et al. as mentioned in this paper used pixel-level simulations that include observing strategy, target selection, supernova properties, and dust to forecast the rates and properties of gLSNe that ZTF and LSST will find.
Abstract: Author(s): Goldstein, DA; Nugent, PE; Goobar, A | Abstract: Supernovae that are strongly gravitationally lensed (gLSNe) by elliptical galaxies are powerful probes of astrophysics and cosmology that will be discovered systematically by wide-field, high-cadence imaging surveys such as the Zwicky Transient Facility (ZTF) and the Large Synoptic Survey Telescope (LSST). Here we use pixel-level simulations that include observing strategy, target selection, supernova properties, and dust to forecast the rates and properties of gLSNe that ZTF and LSST will find. Applying the resolution-insensitive discovery strategy of Goldstein et al., we forecast that ZTF (LSST) can discover 0.02 (0.79) 91bg-like, 0.17 (5.92) 91T-like, 1.22 (47.84) Type Ia, 2.76 (88.51) Type IIP, 0.31 (12.78) Type IIL, and 0.36 (15.43) Type Ib/c gLSNe per year, with uncertainties dominated by uncertainties in the supernova rate. We also forecast that the surveys can discover at least 3.75 (209.32) Type IIn gLSNe per year, for a total of at least 8.60 (380.60) gLSNe per year under fiducial observing strategies. ZTF gLSNe have a median z s = 0.9, z l = 0.35, , Δt max = 10 days, min(θ) = 0.″25, and N img = 4. LSST gLSNe are less compact and less magnified, with a median z s = 1.0, z l = 0.4, , Δt max = 25 days, min(θ) = 0.″6, and N img = 2. We develop a model of the supernova-host galaxy connection and find that the vast majority of gLSN host galaxies will be multiply imaged, enabling detailed constraints on lens models with sufficiently deep high-resolution imaging taken after the supernova has faded. We release the results of our simulations as catalogs at http://portal.nersc.gov/project/astro250/glsne/.
California Institute of Technology1, University of California, Berkeley2, Lawrence Berkeley National Laboratory3, University of Pittsburgh4, Stockholm University5, Royal Institute of Technology6, University of New Hampshire7, Princeton University8, Tel Aviv University9, University of Amsterdam10, University of Arizona11, University of Maryland, College Park12, Academy of Sciences of the Czech Republic13, Spanish National Research Council14, University of Málaga15, Liverpool John Moores University16, Goddard Space Flight Center17, University of Warsaw18, University of Granada19, Russian Academy of Sciences20, Indian Institute of Technology Bombay21, Swinburne University of Technology22, Commonwealth Scientific and Industrial Research Organisation23, University of Sydney24, University of Washington25, University of Wisconsin–Milwaukee26, National Tsing Hua University27
TL;DR: In this article, a photometric red-shift catalog was used to search for optical counterpart to S190814bv and to constrain the ejecta mass of the binary black hole.
Abstract: On 2019 August 14, the Advanced LIGO and Virgo interferometers detected the high-significance gravitational wave (GW) signal S190814bv. The GW data indicated that the event resulted from a neutron star--black hole (NSBH) merger, or potentially a low-mass binary black hole merger. Due to the low false alarm rate and the precise localization (23 deg$^2$ at 90\%), S190814bv presented the community with the best opportunity yet to directly observe an optical/near-infrared counterpart to a NSBH merger. To search for potential counterparts, the GROWTH collaboration performed real-time image subtraction on 6 nights of public Dark Energy Camera (DECam) images acquired in the three weeks following the merger, covering $>$98\% of the localization probability. Using a worldwide network of follow-up facilities, we systematically undertook spectroscopy and imaging of optical counterpart candidates. Combining these data with a photometric redshift catalog, we ruled out each candidate as the counterpart to S190814bv and we placed deep, uniform limits on the optical emission associated with S190814bv. For the nearest consistent GW distance, radiative transfer simulations of NSBH mergers constrain the ejecta mass of S190814bv to be $M_\mathrm{ej} < 0.04$~$M_{\odot}$ at polar viewing angles, or $M_\mathrm{ej} < 0.03$~$M_{\odot}$ if the opacity is $\kappa < 2$~cm$^2$g$^{-1}$. Assuming a tidal deformability for the neutron star at the high end of the range compatible with GW170817 results, our limits would constrain the BH spin component aligned with the orbital momentum to be $ \chi < 0.7$ for mass ratios $Q < 6$, with weaker constraints for more compact neutron stars. We publicly release the photometry from this campaign at this http URL.
California Institute of Technology1, University of Maryland, College Park2, Goddard Space Flight Center3, Lawrence Berkeley National Laboratory4, University of California, Berkeley5, Stockholm University6, Swinburne University of Technology7, Columbia University8, University of Washington9, National Tsing Hua University10
TL;DR: Andreoni et al. as discussed by the authors used the Dark Energy Camera (DECam) to detect binary neutron star (BNS) mergers with 98% probability with the first two months of the Advanced LIGO and Virgo observing run (2019 April-May).
Abstract: Author(s): Andreoni, I; Goldstein, DA; Anand, S; Coughlin, MW; Singer, LP; Ahumada, T; Medford, M; Kool, EC; Webb, S; Bulla, M; Bloom, JS; Kasliwal, MM; Nugent, PE; Bagdasaryan, A; Barnes, J; Cook, DO; Cooke, J; Duev, DA; Fremling, UC; Gatkine, P; Golkhou, VZ; Kong, AKH; Mahabal, A; Martinez-Palomera, J; Tao, D; Zhang, K | Abstract: The first two months of the third Advanced LIGO and Virgo observing run (2019 April-May) showed that distant gravitational-wave (GW) events can now be readily detected. Three candidate mergers containing neutron stars (NS) were reported in a span of 15 days, all likely located more than 100 Mpc away. However, distant events such as the three new NS mergers are likely to be coarsely localized, which highlights the importance of facilities and scheduling systems that enable deep observations over hundreds to thousands of square degrees to detect the electromagnetic counterparts. On 2019 May 10 02:59:39.292 UT the GW candidate S190510g was discovered and initially classified as a binary neutron star (BNS) merger with 98% probability. The GW event was localized within an area of 3462 deg2, later refined to 1166 deg2 (90%) at a distance of 227 92 Mpc. We triggered Target-of-Opportunity observations with the Dark Energy Camera (DECam), a wide-field optical imager mounted at the prime focus of the 4 m Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile. This Letter describes our DECam observations and our real-time analysis results, focusing in particular on the design and implementation of the observing strategy. Within 24 hr of the merger time, we observed 65% of the total enclosed probability of the final skymap with an observing efficiency of 94%. We identified and publicly announced 13 candidate counterparts. S190510g was reclassified 1.7 days after the merger, after our observations were completed, with a "BNS merger" probability reduced from 98% to 42% in favor of a "terrestrial classification.
University of Washington1, Lawrence Berkeley National Laboratory2, University of California, Berkeley3, Queen's University Belfast4, University of Southampton5, University of California, Davis6, Stockholm University7, Space Telescope Science Institute8, University of California, Santa Barbara9, Las Cumbres Observatory Global Telescope Network10
TL;DR: The nature and role of the binary companion of carbon-oxygen white dwarf stars that explode as Type Ia supernovae (SNe Ia) are not yet fully understood as discussed by the authors.
Abstract: The nature and role of the binary companion of carbon-oxygen white dwarf stars that explode as Type Ia supernovae (SNe Ia) are not yet fully understood. Past detections of circumstellar material (C ...
TL;DR: In this paper, the authors describe the observations and automated data movement, data reduction, candidate discovery, and vetting pipeline of their target-of-opportunity DECam observations of S190426c, the first possible neutron star--black hole merger detected via gravitational waves.
Abstract: The discovery of a transient kilonova following the gravitational-wave event GW170817 highlighted the critical need for coordinated rapid and wide-field observations, inference, and follow-up across the electromagnetic spectrum. In the Southern hemisphere, the Dark Energy Camera (DECam) on the Blanco 4-m telescope is well-suited to this task, as it is able to cover wide-fields quickly while still achieving the depths required to find kilonovae like the one accompanying GW170817 to $\sim$500 Mpc, the binary neutron star horizon distance for current generation of LIGO/Virgo collaboration (LVC) interferometers. Here, as part of the multi-facility followup by the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration, we describe the observations and automated data movement, data reduction, candidate discovery, and vetting pipeline of our target-of-opportunity DECam observations of S190426c, the first possible neutron star--black hole merger detected via gravitational waves. Starting 7.5hr after S190426c, over 11.28\,hr of observations, we imaged an area of 525\,deg$^2$ ($r$-band) and 437\,deg$^2$ ($z$-band); this was 16.3\% of the total original localization probability and nearly all of the probability density visible from the Southern hemisphere. The machine-learning based pipeline was optimized for fast turnaround, delivering transient candidates for human vetting within 17 minutes, on average, of shutter closure. We reported nine promising counterpart candidates 2.5 hours before the end of our observations. Our observations yielded no detection of a bona fide counterpart to $m_z = 22.5$ and $m_r = 22.9$ at the 5$\sigma$ level of significance, consistent with the refined LVC positioning. We view these observations and rapid inferencing as an important real-world test for this novel end-to-end wide-field pipeline.
Lawrence Berkeley National Laboratory1, Carnegie Institution for Science2, Yale University3, University of Rochester4, University of California, Berkeley5, École Polytechnique6, University College London7, Fermilab8, Tsinghua University9, University of Arizona10, University of Michigan11, Perimeter Institute for Theoretical Physics12, University of California, Santa Cruz13, Ohio State University14, Siena College15, University of Wyoming16, University of Pittsburgh17, New York University18, Max Planck Society19, Kansas State University20, Ohio University21, University of Florida22, Brandeis University23, Stanford University24
TL;DR: Schlegel, David J; Kollmeier, Juna A; Aldering, Greg; Bailey, Stephen; Baltay, Charles; Bebek, Christopher; BenZvi, Segev; Besuner, Robert; Blanc, Guillermo; Jelinsky, Patrick; Johns, Matthew; Karagiannis, Dionysios; Kent, Stephen M; Kim, Alex G; Kneib, Jean-Paul; Kronig, Luzius; Konidaris, Nick; Lahav, Ofer; Lampton, Michael L; Lang,
Abstract: Author(s): Schlegel, David J; Kollmeier, Juna A; Aldering, Greg; Bailey, Stephen; Baltay, Charles; Bebek, Christopher; BenZvi, Segev; Besuner, Robert; Blanc, Guillermo; Bolton, Adam S; Bouri, Mohamed; Brooks, David; Buckley-Geer, Elizabeth; Cai, Zheng; Crane, Jeffrey; Dey, Arjun; Doel, Peter; Fan, Xiaohui; Ferraro, Simone; Font-Ribera, Andreu; Gutierrez, Gaston; Guy, Julien; Heetderks, Henry; Huterer, Dragan; Infante, Leopoldo; Jelinsky, Patrick; Johns, Matthew; Karagiannis, Dionysios; Kent, Stephen M; Kim, Alex G; Kneib, Jean-Paul; Kronig, Luzius; Konidaris, Nick; Lahav, Ofer; Lampton, Michael L; Lang, Dustin; Leauthaud, Alexie; Liguori, Michele; Linder, Eric V; Magneville, Christophe; Martini, Paul; Mateo, Mario; McDonald, Patrick; Miller, Christopher J; Moustakas, John; Myers, Adam D; Mulchaey, John; Newman, Jeffrey A; Nugent, Peter E; Palanque-Delabrouille, Nathalie; Padmanabhan, Nikhil; Piro, Anthony L; Poppett, Claire; Prochaska, Jason X; Pullen, Anthony R; Rabinowitz, David; Ramirez, Solange; Rix, Hans-Walter; Ross, Ashley J; Samushia, Lado; Schaan, Emmanuel; Schubnell, Michael; Seljak, Uros; Seo, Hee-Jong; Shectman, Stephen A; Silber, Joseph; Simon, Joshua D; Slepian, Zachary; Soares-Santos, Marcelle; Tarle, Greg; Thompson, Ian; Valluri, Monica; Wechsler, Risa H; White, Martin; Wilson, Michael J; Yeche, Christophe; Zaritsky, Dennis | Abstract: MegaMapper is a proposed ground-based experiment to measure Inflation parameters and Dark Energy from galaxy redshifts at 2
TL;DR: In this article, the authors use non-local thermal equilibrium radiative transport modeling to examine observational signatures of sub-Chandrasekhar mass double detonation explosions in the nebular phase.
Abstract: We use non-local thermal equilibrium radiative transport modeling to examine observational signatures of sub-Chandrasekhar mass double detonation explosions in the nebular phase. Results range from spectra that look like typical and subluminous Type Ia supernovae (SNe) for higher mass progenitors to spectra that look like Ca-rich transients for lower mass progenitors. This ignition mechanism produces an inherent relationship between emission features and the progenitor mass as the ratio of the nebular [Ca II]/[Fe III] emission lines increases with decreasing white dwarf mass. Examining the [Ca II]/[Fe III] nebular line ratio in a sample of observed SNe we find further evidence for the two distinct classes of SNe Ia identified in Polin et al. by their relationship between Si II velocity and B-band magnitude, both at time of peak brightness. This suggests that SNe Ia arise from more than one progenitor channel, and provides an empirical method for classifying events based on their physical origin. Furthermore, we provide insight to the mysterious origin of Ca-rich transients. Low-mass double detonation models with only a small mass fraction of Ca (1%) produce nebular spectra that cool primarily through forbidden [Ca II] emission.