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Showing papers by "Peter Nugent published in 2020"


Journal ArticleDOI
TL;DR: In this paper, the authors used a photometric redshift catalog and radiative transfer simulations of NSBH mergers to constrain the ejecta mass of S190814bv to be $M_\mathrm{ej} < 0.04$~$M_{\odot}$ at polar viewing angles, or if the opacity is $\kappa < 2$~cm$^2$g$^{-1}$.
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 http://www.astro.caltech.edu/~danny/static/s190814bv.

79 citations


Journal ArticleDOI
TL;DR: Coppejans et al. as discussed by the authors presented X-ray and radio observations of the Fast Blue Optical Transient CRTS-CSS161010 J045834-081803 at t = 69-531 days.
Abstract: Author(s): Coppejans, DL; Margutti, R; Terreran, G; Nayana, AJ; Coughlin, ER; Laskar, T; Alexander, KD; Bietenholz, M; Caprioli, D; Chandra, P; Drout, MR; Frederiks, D; Frohmaier, C; Hurley, KH; Kochanek, CS; MacLeod, M; Meisner, A; Nugent, PE; Ridnaia, A; Sand, DJ; Svinkin, D; Ward, C; Yang, S; Baldeschi, A; Chilingarian, IV; Dong, Y; Esquivia, C; Fong, W; Guidorzi, C; Lundqvist, P; Milisavljevic, D; Paterson, K; Reichart, DE; Shappee, B; Stroh, MC; Valenti, S; Zauderer, BA; Zhang, B | Abstract: We present X-ray and radio observations of the Fast Blue Optical Transient CRTS-CSS161010 J045834-081803 (CSS161010 hereafter) at t = 69-531 days. CSS161010 shows luminous X-ray (L x ∼ 5 × 1039 erg s-1) and radio (L ν ∼ 1029 erg s-1 Hz-1) emission. The radio emission peaked at ∼100 days post-transient explosion and rapidly decayed. We interpret these observations in the context of synchrotron emission from an expanding blast wave. CSS161010 launched a mildly relativistic outflow with velocity Γβc ≥ 0.55c at ∼100 days. This is faster than the non-relativistic AT 2018cow (Γβc ∼ 0.1c) and closer to ZTF18abvkwla (Γβc ≥ 0.3c at 63 days). The inferred initial kinetic energy of CSS161010 (E k ⪆ 1051 erg) is comparable to that of long gamma-ray bursts, but the ejecta mass that is coupled to the mildly relativistic outflow is significantly larger (∼ 0.01-0.1 M⊙). This is consistent with the lack of observed γ-rays. The luminous X-rays were produced by a different emission component to the synchrotron radio emission. CSS161010 is located at ∼150 Mpc in a dwarf galaxy with stellar mass M * ∼ 107 M o˙ and specific star formation rate sSFR ∼ 0.3 Gyr-1. This mass is among the lowest inferred for host galaxies of explosive transients from massive stars. Our observations of CSS161010 are consistent with an engine-driven aspherical explosion from a rare evolutionary path of a H-rich stellar progenitor, but we cannot rule out a stellar tidal disruption event on a centrally located intermediate-mass black hole. Regardless of the physical mechanism, CSS161010 establishes the existence of a new class of rare (rate l 0.4% of the local core-collapse supernova rate) H-rich transients that can launch mildly relativistic outflows.

64 citations


Journal ArticleDOI
M. Smith1, Mark Sullivan1, P. Wiseman1, Richard Kessler2, Daniel Scolnic3, D. J. Brout4, C. B. D'Andrea4, C. B. D'Andrea5, Tamara M. Davis6, Ryan J. Foley7, C. Frohmaier8, Lluís Galbany9, R. R. Gupta10, Claudia P. Gutiérrez1, Samuel Hinton6, L. Kelsey1, C. Lidman11, E. Macaulay12, E. Macaulay8, Anais Möller13, Anais Möller11, Robert C. Nichol8, Peter Nugent10, Peter Nugent14, Antonella Palmese2, Antonella Palmese15, M. Pursiainen1, M. Sako4, E. Swann8, R. C. Thomas10, Brad E. Tucker11, M. Vincenzi8, Daniela Carollo16, Geraint F. Lewis17, N. E. Sommer11, T. M. C. Abbott, Michel Aguena18, S. Allam15, Santiago Avila19, E. Bertin20, Sunayana Bhargava21, David J. Brooks22, E. Buckley-Geer15, D. L. Burke23, D. L. Burke24, A. Carnero Rosell, M. Carrasco Kind25, M. Carrasco Kind26, M. Costanzi16, L. N. da Costa, J. De Vicente, S. Desai27, H. T. Diehl15, Peter Doel22, Tim Eifler28, Tim Eifler29, S. Everett7, B. Flaugher15, Pablo Fosalba30, Josh Frieman2, Josh Frieman15, Juan Garcia-Bellido19, Enrique Gaztanaga30, Karl Glazebrook31, Daniel Gruen23, Daniel Gruen24, Robert A. Gruendl25, Robert A. Gruendl26, J. Gschwend, G. Gutierrez15, W. G. Hartley32, W. G. Hartley33, W. G. Hartley22, D. L. Hollowood7, K. Honscheid34, David J. James35, Elisabeth Krause29, Kyler Kuehn36, Kyler Kuehn37, N. Kuropatkin15, Marcus Lima18, Niall MacCrann34, M. A. G. Maia, Jennifer L. Marshall38, Paul Martini34, Peter Melchior39, Felipe Menanteau26, Felipe Menanteau25, Ramon Miquel40, Ramon Miquel41, F. Paz-Chinchón25, F. Paz-Chinchón42, A. A. Plazas39, A. K. Romer21, A. Roodman24, A. Roodman23, Eli S. Rykoff24, Eli S. Rykoff23, E. J. Sanchez, V. Scarpine15, Michael Schubnell43, S. Serrano30, I. Sevilla-Noarbe, E. Suchyta44, M. E. C. Swanson25, G. Tarle43, Daniel Thomas8, Douglas L. Tucker15, T. N. Varga45, T. N. Varga46, A. R. Walker 
TL;DR: In this article, the authors present improved photometric measurements for the host galaxies of 206 spectroscopically confirmed type Ia supernovae discovered by the Dark Energy Survey Supernova Program (DES-SN) and used in the first DES-SN cosmological analysis.
Abstract: We present improved photometric measurements for the host galaxies of 206 spectroscopically confirmed type Ia supernovae discovered by the Dark Energy Survey Supernova Program (DES-SN) and used in the first DES-SN cosmological analysis. For the DES-SN sample, when considering a 5D (z, x(1), c, alpha, #) bias correction, we find evidence of a Hubble residual 'mass step', where SNe Ia in high-mass galaxies (>10(10)M(circle dot)) are intrinsically more luminous (after correction) than their low-mass counterparts by gamma = 0.040 +/- 0.019 mag. This value is larger by 0.031 mag than the value found in the first DES-SN cosmological analysis. This difference is due to a combination of updated photometric measurements and improved star formation histories and is not from host-galaxy misidentification. When using a 1D (redshift-only) bias correction the inferred mass step is larger, with gamma = 0.066 +/- 0.020 mag. The 1D-5D gamma difference for DES-SN is 0.026 +/- 0.009 mag. We show that this difference is due to a strong correlation between host galaxy stellar mass and the x(1) component of the 5D distance-bias correction. Including an intrinsic correlation between the observed properties of SNe Ia, stretch and colour, and stellar mass in simulated SN Ia samples, we show that a 5D fit recovers gamma with -9 mmag bias compared to a +2 mmag bias for a 1D fit. This difference can explain part of the discrepancy seen in the data. Improvements in modelling correlations between galaxy properties and SN is necessary to ensure unbiased precision estimates of the dark energy equation of state as we enter the era of LSST.

59 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented the photometric properties of SLSN host galaxies from the far-ultraviolet to the mid-infrared and model the host-galaxy spectral energy distributions to derive physical properties.
Abstract: Several thousand core-collapse supernovae (CCSNe) of different flavors have been discovered so far. However, identifying their progenitors has remained an outstanding open question in astrophysics. Studies of SN host galaxies have proven to be powerful in providing constraints on the progenitor populations. In this paper, we present all CCSNe detected between 2009 and 2017 by the Palomar Transient Factory. This sample includes 888 SNe of 12 distinct classes out to redshift $z\approx1$. We present the photometric properties of their host galaxies from the far-ultraviolet to the mid-infrared and model the host-galaxy spectral energy distributions to derive physical properties. The galaxy mass functions of Type Ic, Ib, IIb, II, and IIn SNe ranges from $10^{5}$ to $10^{11.5}~M_\odot$, probing the entire mass range of star-forming galaxies down to the least-massive star-forming galaxies known. Moreover, the galaxy mass distributions are consistent with models of star-formation-weighted mass functions. Regular CCSNe are hence direct tracers of star formation. Small but notable differences exist between some of the SN classes. Type Ib/c SNe prefer galaxies with slightly higher masses (i.e., higher metallicities) and star-formation rates than Type IIb and II SNe. These differences are less pronounced than previously thought. H-poor SLSNe and SNe~Ic-BL are scarce in galaxies above $10^{10}~M_\odot$. Their progenitors require environments with metallicities of $<0.4$ and $<1$ solar, respectively. In addition, the hosts of H-poor SLSNe are dominated by a younger stellar population than all other classes of CCSNe. Our findings corroborate the notion that low-metallicity \textit{and} young age play an important role in the formation of SLSN progenitors.

42 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used forced-photometry light curves for 196 interacting supernovae (SNe), mostly of Type IIn, detected by the Zwicky Transient Facility between early 2018 and June 2020, to identify and characterize pre-explosion outbursts.
Abstract: Interaction-powered supernovae (SNe) explode within an optically-thick circumstellar medium (CSM) that could be ejected during eruptive events. To identify and characterize such pre-explosion outbursts we produce forced-photometry light curves for 196 interacting SNe, mostly of Type IIn, detected by the Zwicky Transient Facility between early 2018 and June 2020. Extensive tests demonstrate that we only expect a few false detections among the 70,000 analyzed pre-explosion images after applying quality cuts and bias corrections. We detect precursor eruptions prior to 18 Type IIn SNe and prior to the Type Ibn SN2019uo. Precursors become brighter and more frequent in the last months before the SN and month-long outbursts brighter than magnitude -13 occur prior to 25% (5 - 69%, 95% confidence range) of all Type IIn SNe within the final three months before the explosion. With radiative energies of up to $10^{49}\,\text{erg}$, precursors could eject $\sim1\,\text{M}_\odot$ of material. Nevertheless, SNe with detected precursors are not significantly more luminous than other SNe IIn and the characteristic narrow hydrogen lines in their spectra typically originate from earlier, undetected mass-loss events. The long precursor durations require ongoing energy injection and they could, for example, be powered by interaction or by a continuum-driven wind. Instabilities during the neon and oxygen burning phases are predicted to launch precursors in the final years to months before the explosion; however, the brightest precursor is 100 times more energetic than anticipated.

36 citations


Journal ArticleDOI
TL;DR: In this article, a Bayesian framework was developed to model the early rise of Type Ia supernovae as a power law in time, which enables the inclusion of priors in the model.
Abstract: While it is clear that Type Ia supernovae (SNe) are the result of thermonuclear explosions in C/O white dwarfs (WDs), a great deal remains uncertain about the binary companion that facilitates the explosive disruption of the WD. Here, we present a comprehensive analysis of a large, unique data set of 127 SNe$\,$Ia with exquisite coverage by the Zwicky Transient Facility (ZTF). High-cadence (six observations per night) ZTF observations allow us to measure the SN rise time and examine its initial evolution. We develop a Bayesian framework to model the early rise as a power law in time, which enables the inclusion of priors in our model. For a volume-limited subset of normal SNe$\,$Ia, we find that the mean power-law index is consistent with 2 in the $r_\mathrm{ZTF}$-band ($\alpha_r = 2.01\pm0.02$), as expected in the expanding fireball model. There are, however, individual SNe that are clearly inconsistent with $\alpha_r=2$. We estimate a mean rise time of 18.9$\,$d (with a range extending from $\sim$15 to 22$\,$d), though this is subject to the adopted prior. We identify an important, previously unknown, bias whereby the rise times for higher-redshift SNe within a flux-limited survey are systematically underestimated. This effect can be partially alleviated if the power-law index is fixed to $\alpha=2$, in which case we estimate a mean rise time of 21.7$\,$d (with a range from $\sim$18 to 23$\,$d). The sample includes a handful of rare and peculiar SNe$\,$Ia. Finally, we conclude with a discussion of lessons learned from the ZTF sample that can eventually be applied to observations from the Vera C. Rubin Observatory.

29 citations


Journal ArticleDOI
M. Smith1, M. Smith2, M. Smith3, C. B. D'Andrea, Mark Sullivan3, Anais Möller4, Robert C. Nichol, R. C. Thomas5, A. G. Kim5, M. Sako6, F. J. Castander7, Alexei V. Filippenko8, Alexei V. Filippenko9, Ryan J. Foley10, Lluís Galbany11, Santiago González-Gaitán12, E. Kasai13, Robert P. Kirshner14, Robert P. Kirshner15, C. Lidman16, Daniel Scolnic17, D. J. Brout6, Tamara M. Davis18, R. R. Gupta5, Samuel Hinton18, Richard Kessler19, J. Lasker19, Edward Macaulay, R. C. Wolf20, Bonnie Zhang16, Jacobo Asorey, Arturo Avelino15, Bruce A. Bassett21, Bruce A. Bassett22, J. Calcino18, Daniela Carollo, Ricard Casas7, P. Challis15, M. Childress3, Alejandro Clocchiatti23, Steven M. Crawford24, C. Frohmaier, Karl Glazebrook25, David Goldstein26, Melissa L. Graham27, J. K. Hoormann18, Kyler Kuehn28, Kyler Kuehn29, Geraint F. Lewis30, Kaisey S. Mandel31, Eric Morganson32, Daniel Muthukrishna16, Daniel Muthukrishna31, Peter Nugent5, Yen-Chen Pan33, M. Pursiainen3, Rob Sharp16, N. E. Sommer16, E. Swann, B. P. Thomas34, B. E. Tucker16, S. A. Uddin34, P. Wiseman3, WeiKang Zheng9, T. M. C. Abbott, J. Annis35, Santiago Avila36, Keith Bechtol37, Gary Bernstein6, E. Bertin38, E. Bertin39, David J. Brooks40, D. L. Burke20, A. Carnero Rosell41, A. Carnero Rosell7, M. Carrasco Kind32, J. Carretero, Carlos E. Cunha20, L. N. da Costa, C. Davis20, J. De Vicente, H. T. Diehl35, Tim Eifler42, Tim Eifler26, Juan Estrada35, Josh Frieman35, Josh Frieman19, Juan Garcia-Bellido36, Enrique Gaztanaga7, D. W. Gerdes43, Daniel Gruen20, Robert A. Gruendl32, J. Gschwend, G. Gutierrez35, W. G. Hartley44, W. G. Hartley40, W. G. Hartley45, D. L. Hollowood10, K. Honscheid46, Ben Hoyle, David J. James15, M. W. G. Johnson32, M. D. Johnson32, N. Kuropatkin35, Tenglin Li47, Tenglin Li48, Marcos Lima49, M. A. G. Maia, M. March6, Jennifer L. Marshall50, Paul Martini15, Paul Martini46, Felipe Menanteau32, Christopher J. Miller43, Ramon Miquel, Eric H. Neilsen35, R. L. C. Ogando, A. A. Plazas48, A. K. Romer51, E. J. Sanchez, V. Scarpine35, Michael Schubnell43, S. Serrano7, I. Sevilla-Noarbe, M. Soares-Santos43, Flavia Sobreira52, E. Suchyta53, G. Tarle43, Douglas L. Tucker35, W. C. Wester35 
University of Lyon1, Claude Bernard University Lyon 12, University of Southampton3, University of Auvergne4, Lawrence Berkeley National Laboratory5, University of Pennsylvania6, Spanish National Research Council7, Cornell University8, University of California, Berkeley9, University of California, Santa Cruz10, University of Granada11, University of Lisbon12, University of Namibia13, Gordon and Betty Moore Foundation14, Harvard University15, Australian National University16, Duke University17, University of Queensland18, University of Chicago19, Stanford University20, University of Cape Town21, African Institute for Mathematical Sciences22, Pontifical Catholic University of Chile23, Space Telescope Science Institute24, Swinburne University of Technology25, California Institute of Technology26, University of Washington27, Lowell Observatory28, Macquarie University29, University of Sydney30, University of Cambridge31, University of Illinois at Urbana–Champaign32, National Central University33, University of Texas at Austin34, Fermilab35, Autonomous University of Madrid36, University of Wisconsin-Madison37, Institut d'Astrophysique de Paris38, University of Paris39, University College London40, University of La Laguna41, University of Arizona42, University of Michigan43, ETH Zurich44, University of Geneva45, Ohio State University46, Carnegie Institution for Science47, Princeton University48, University of São Paulo49, Texas A&M University50, University of Sussex51, State University of Campinas52, Oak Ridge National Laboratory53
TL;DR: The first three seasons of the DES-SN3YR data were used for the first cosmology analysis as mentioned in this paper, the results of which are given in Dark Energy Survey Collaboration et al.
Abstract: We present details on the observing strategy, data-processing techniques, and spectroscopic targeting algorithms for the first three years of operation for the Dark Energy Survey Supernova Program (DES-SN). This five-year program using the Dark Energy Camera mounted on the 4 m Blanco telescope in Chile was designed to discover and follow supernovae (SNe) Ia over a wide redshift range (0.05 < z < 1.2) to measure the equation-of-state parameter of dark energy. We describe the SN program in full: Strategy, observations, data reduction, spectroscopic follow-up observations, and classification. From three seasons of data, we have discovered 12,015 likely SNe, 308 of which have been spectroscopically confirmed, including 251 SNe Ia over a redshift range of 0.017 < z < 0.85. We determine the effective spectroscopic selection function for our sample and use it to investigate the redshiftdependent bias on the distance moduli of SNe Ia we have classified. The data presented here are used for the first cosmology analysis by DES-SN ("DES-SN3YR"), the results of which are given in Dark Energy Survey Collaboration et al. The 489 spectra that are used to define the DES-SN3YR sample are publicly available at https://des.ncsa.illinois.edu/releases/sn.

27 citations


Journal ArticleDOI
TL;DR: In this article, the authors present new optical to mid-infrared photometry and optical spectroscopy for the M31-LRN-2015 stellar merger discovered in the Andromeda Galaxy in 2015.
Abstract: Author(s): Blagorodnova, N; Karambelkar, V; Adams, SM; Kasliwal, MM; Kochanek, CS; Dong, S; Campbell, H; Hodgkin, S; Jencson, JE; Johansson, J; Kozlowski, S; Laher, RR; Masci, F; Nugent, P; Rebbapragada, U | Abstract: ABSTRACT M31-LRN-2015 is a likely stellar merger discovered in the Andromeda Galaxy in 2015. We present new optical to mid-infrared photometry and optical spectroscopy for this event. Archival data show that the source started to brighten ∼2nyr before the nova event. During this precursor phase, the source brightened by ∼3 mag. The light curve at 6 and 1.5 months before the main outburst may show periodicity, with periods of 16n±n0.3 and 28.1n±n1.4 d, respectively. This complex emission may be explained by runaway mass-loss from the system after the binary undergoes Roche lobe overflow, leading the system to coalesce in tens of orbital periods. While the progenitor spectral energy distribution shows no evidence of pre-existing warm dust in the system, the remnant forms an optically thick dust shell at approximately four months after the outburst peak. The optical depth of the shell increases dramatically after 1.5 yr, suggesting the existence of shocks that enhance the dust formation process. We propose that the merger remnant is likely an inflated giant obscured by a cooling shell of gas with mass ∼0.2 M⊙ ejected at the onset of the common envelope phase.

26 citations


Journal ArticleDOI
TL;DR: In this paper, the colors of 65 Type Ia supernovae discovered within 5 days from first light by the Zwicky Transient Facility in 2018, a sample that is about three times larger than that in the literature.
Abstract: Colors of Type Ia supernovae in the first few days after explosion provide a potential discriminant between different models. In this paper, we present $g-r$ colors of 65 Type Ia supernovae discovered within 5 days from first light by the Zwicky Transient Facility in 2018, a sample that is about three times larger than that in the literature. We find that $g-r$ colors are intrinsically rather homogeneous at early phases, with about half of the dispersion attributable to photometric uncertainties ($\sigma_\mathrm{noise}\sim\sigma_\mathrm{int}\sim$ 0.18 mag). Colors are nearly constant starting from 6 days after first light ($g-r\sim-0.15$ mag), while the time evolution at earlier epochs is characterized by a continuous range of slopes, from events rapidly transitioning from redder to bluer colors (slope of $\sim-0.25$ mag day$^{-1}$) to events with a flatter evolution. The continuum in the slope distribution is in good agreement both with models requiring some amount of $^{56}$Ni mixed in the outermost regions of the ejecta and with "double-detonation" models having thin helium layers ($M_\mathrm{He}=0.01\,M_\odot$) and varying carbon-oxygen core masses. At the same time, six events show evidence for a distinctive "red bump" signature predicted by "double-detonation" models with larger helium masses. We finally identify a significant correlation between the early-time $g-r$ slopes and supernova brightness, with brighter events associated to flatter color evolution (p-value=0.006). The distribution of slopes, however, is consistent with being drawn from a single population, with no evidence for two components as claimed in the literature based on $B-V$ colors.

23 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used a Monte Carlo simulation of hundreds of millions of SN light curve realizations coupled with the detailed PTF survey detection efficiencies to forward-model the SN rates in PTF.
Abstract: We present measurements of the local core collapse supernova (SN) rate using SN discoveries from the Palomar Transient Factory (PTF). We use a Monte Carlo simulation of hundreds of millions of SN light curve realizations coupled with the detailed PTF survey detection efficiencies to forward-model the SN rates in PTF. Using a sample of 86 core collapse SNe, including 26 stripped-envelope SNe (SESNe), we show that the overall core collapse SN volumetric rate is $r^\mathrm{CC}_v=9.10_{-1.27}^{+1.56}\times10^{-5}\,\text{SNe yr}^{-1}\,\text{Mpc}^{-3}\, h_{70}^{3}$ at $ \langle z \rangle = 0.028$, and the SESN volumetric rate is $r^\mathrm{SE}_v=2.41_{-0.64}^{+0.81}\times10^{-5}\, \text{SNe yr}^{-1}\,\text{Mpc}^{-3}\, h_{70}^{3}$. We further measure a volumetric rate for hydrogen-free superluminous SNe (SLSNe-I) using 8 events at $z{\le}0.2$ of $r^\mathrm{SLSN-I}_v=35_{-13}^{+25}\, \text{SNe yr}^{-1}\text{Gpc}^{-3}\, h_{70}^{3}$, which represents the most precise SLSN-I rate measurement to date. Using a simple cosmic star-formation history to adjust these volumetric rate measurements to the same redshift, we measure a local ratio of SLSN-I to SESN of $\sim1/810^{+1500}_{-94}$, and of SLSN-I to all CCSN types of $\sim 1/3500^{+2800}_{-720}$. However, using host galaxy stellar mass as a proxy for metallicity, we also show that this ratio is strongly metallicity dependent: in low-mass ($\mathrm{log} M_{*} < 9.5 \mathrm{M}_\odot$) galaxies, which are the only environments that host SLSN-I in our sample, we measure a SLSN-I to SESN fraction of $1/300^{+380}_{-170}$ and $1/1700^{+1800}_{-720}$ for all CCSN. We further investigate the SN rates a function of host galaxy stellar mass and show that the specific rates of all core collapse SNe decrease with increasing stellar mass.

21 citations


Journal ArticleDOI
TL;DR: Miller et al. as discussed by the authors developed a Bayesian framework to model the early rise of Type Ia supernovae as a power law in time, which enables the inclusion of priors in their model.
Abstract: Author(s): Miller, AA; Yao, Y; Bulla, M; Pankow, C; Bellm, EC; Cenko, SB; Dekany, R; Fremling, C; Graham, MJ; Kupfer, T; Laher, RR; Mahabal, AA; Masci, FJ; Nugent, PE; Riddle, R; Rusholme, B; Smith, RM; Shupe, DL; Roestel, JV; Kulkarni, SR | Abstract: While it is clear that Type Ia supernovae (SNe) are the result of thermonuclear explosions in C/O white dwarfs (WDs), a great deal remains uncertain about the binary companion that facilitates the explosive disruption of the WD. Here, we present a comprehensive analysis of a large, unique data set of 127 SNe Ia with exquisite coverage by the Zwicky Transient Facility (ZTF). High-cadence (six observations per night) ZTF observations allow us to measure the SN rise time and examine its initial evolution. We develop a Bayesian framework to model the early rise as a power law in time, which enables the inclusion of priors in our model. For a volume-limited subset of normal SNe Ia, we find that the mean power-law index is consistent with 2 in the r ZTF-band (α r=2.01± 0.02), as expected in the expanding fireball model. There are, however, individual SNe that are clearly inconsistent with α r=2. We estimate a mean rise time of 18.9 days (with a range extending from ∼15 to 22 days), though this is subject to the adopted prior. We identify an important, previously unknown, bias whereby the rise times for higher-redshift SNe within a flux-limited survey are systematically underestimated. This effect can be partially alleviated if the power-law index is fixed to α = 2, in which case we estimate a mean rise time of 21.7 days (with a range from ∼18 to 23 days). The sample includes a handful of rare and peculiar SNe Ia. Finally, we conclude with a discussion of lessons learned from the ZTF sample that can eventually be applied to observations from the Vera C. Rubin Observatory.

Journal ArticleDOI
TL;DR: In this article, the authors describe the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey, which showed the presence of weak and narrow features arising from interaction with circumstellar material.
Abstract: This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 ± 0.9 d to reach a peak brightness of −19.70 ± 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow HeI HeI features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow HeI HeI velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive 56Ni powering but can be explained through a combination of CSM interaction and an underlying 56Ni decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib.

Posted Content
TL;DR: This work presents scalable hybrid-parallel algorithms for training large-scale 3D convolutional neural networks, and enables training of CosmoFlow with much larger samples than previously possible, realizing an order-of-magnitude improvement in prediction accuracy.
Abstract: We present scalable hybrid-parallel algorithms for training large-scale 3D convolutional neural networks. Deep learning-based emerging scientific workflows often require model training with large, high-dimensional samples, which can make training much more costly and even infeasible due to excessive memory usage. We solve these challenges by extensively applying hybrid parallelism throughout the end-to-end training pipeline, including both computations and I/O. Our hybrid-parallel algorithm extends the standard data parallelism with spatial parallelism, which partitions a single sample in the spatial domain, realizing strong scaling beyond the mini-batch dimension with a larger aggregated memory capacity. We evaluate our proposed training algorithms with two challenging 3D CNNs, CosmoFlow and 3D U-Net. Our comprehensive performance studies show that good weak and strong scaling can be achieved for both networks using up 2K GPUs. More importantly, we enable training of CosmoFlow with much larger samples than previously possible, realizing an order-of-magnitude improvement in prediction accuracy.

Journal ArticleDOI
TL;DR: Hsiao et al. as discussed by the authors showed that the optical spectrum is typical of a super-Chandrasekhar-like SN Ia, but the light curves are unlike those of any SNe Ia observed.
Abstract: Author(s): Hsiao, EY; Hoeflich, P; Ashall, C; Lu, J; Contreras, C; Burns, CR; Phillips, MM; Galbany, L; Anderson, JP; Baltay, C; Baron, E; Castellon, S; Davis, S; Freedman, WL; Gall, C; Gonzalez, C; Graham, ML; Hamuy, M; Holoien, TWS; Karamehmetoglu, E; Krisciunas, K; Kumar, S; Kuncarayakti, H; Morrell, N; Moriya, TJ; Nugent, PE; Perlmutter, S; Persson, SE; Piro, AL; Rabinowitz, D; Roth, M; Shahbandeh, M; Shappee, BJ; Stritzinger, MD; Suntzeff, NB; Taddia, F; Uddin, SA | Abstract: The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties that may help to reveal the origin of the "super-Chandrasekhar"(or 03fg-like) group. The optical spectrum is typical of a 03fg-like SN Ia, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At -23 rest-frame days relative to B-band maximum, LSQ14fmg is already brighter than MV = -19 mag before host extinction correction. The observed color curves show a flat evolution from the earliest observation to approximately 1 week after maximum. The near-infrared light curves peak brighter than -20.5 mag in the J and H bands, far more luminous than any 03fg-like SNe Ia with near-infrared observations. At 1 month past maximum, the optical light curves decline rapidly. The early, slow rise and flat color evolution are interpreted to result from an additional excess flux from a power source other than the radioactive decay of the synthesized 56Ni. The excess flux matches the interaction with a typical superwind of an asymptotic giant branch (AGB) star in density structure, mass-loss rate, and duration. The rapid decline starting at around 1 month past B-band maximum may be an indication of rapid cooling by active carbon monoxide (CO) formation, which requires a low-temperature and high-density environment. These peculiarities point to an AGB progenitor near the end of its evolution and the core degenerate scenario as the likely explosion mechanism for LSQ14fmg.

Journal ArticleDOI
TL;DR: Bulla et al. as mentioned in this paper found that g-r colors are intrinsically rather homogeneous at early phases, with about half of the dispersion attributable to photometric uncertainties (σnoise ∼ σ int ∼ 0.18 mag).
Abstract: Author(s): Bulla, M; Miller, AA; Yao, Y; Dessart, L; Dhawan, S; Papadogiannakis, S; Biswas, R; Goobar, A; Kulkarni, SR; Nordin, J; Nugent, P; Polin, A; Sollerman, J; Bellm, EC; Coughlin, MW; Dekany, R; Golkhou, VZ; Graham, MJ; Kasliwal, MM; Kupfer, T; Laher, RR; Masci, FJ; Porter, M; Rusholme, B; Shupe, DL | Abstract: Colors of Type Ia supernovae (SNe Ia) in the first few days after explosion provide a potential discriminant between different models. In this paper, we present g-r colors of 65 SNe Ia discovered within 5 days from first light by the Zwicky Transient Facility in 2018, a sample that is about three times larger than that in the literature. We find that g-r colors are intrinsically rather homogeneous at early phases, with about half of the dispersion attributable to photometric uncertainties (σnoise ∼ σ int ∼ 0.18 mag). Colors are nearly constant starting from 6 days after first light (g-r ∼-0.15 mag), while the time evolution at earlier epochs is characterized by a continuous range of slopes, from events rapidly transitioning from redder to bluer colors (slope of ∼-0.25 mag day-1) to events with a flatter evolution. The continuum in the slope distribution is in good agreement both with models requiring some amount of 56Ni mixed in the outermost regions of the ejecta and with "double-detonation"models having thin helium layers MHe=0.01 M⊙) and varying carbon-oxygen core masses. At the same time, six events show evidence for a distinctive "red bump"signature predicted by double-detonation models with larger helium masses. We finally identify a significant correlation between the early-time g-r slopes and supernova brightness, with brighter events associated to flatter color evolution (p-value = 0.006). The distribution of slopes, however, is consistent with being drawn from a single population, with no evidence for two components as claimed in the literature based on B-V colors.

Journal ArticleDOI
TL;DR: In this paper, the authors present observations of SN 2018fif (ZTF 18abokyfk) and employ the SOPRANOS code, an implementation of the model by Sapir & Waxman and its extension to early times by Morag et al.
Abstract: High-cadence transient surveys are able to capture supernovae closer to their first light than ever before. Applying analytical models to such early emission, we can constrain the progenitor stars' properties. In this paper, we present observations of SN 2018fif (ZTF 18abokyfk). The supernova was discovered close to first light and monitored by the Zwicky Transient Facility (ZTF) and the Neil Gehrels Swift Observatory. Early spectroscopic observations suggest that the progenitor of SN 2018fif was surrounded by relatively small amounts of circumstellar material compared to all previous cases. This particularity, coupled with the high-cadence multiple-band coverage, makes it a good candidate to investigate using shock-cooling models. We employ the SOPRANOS code, an implementation of the model by Sapir & Waxman and its extension to early times by Morag et al. Compared with previous implementations, SOPRANOS has the advantage of including a careful account of the limited temporal validity domain of the shock-cooling model as well as allowing usage of the entirety of the early UV data. We find that the progenitor of SN 2018fif was a large red supergiant with a radius of $R={744.0}_{-128.0}^{+183.0}\,{R}_{\odot }$ and an ejected mass of ${M}_{\mathrm{ej}}={9.3}_{-5.8}^{+0.4}\,{M}_{\odot }$. Our model also gives information on the explosion epoch, the progenitor's inner structure, the shock velocity, and the extinction. The distribution of radii is double-peaked, with smaller radii corresponding to lower values of the extinction, earlier recombination times, and a better match to the early UV data. If these correlations persist in future objects, denser spectroscopic monitoring constraining the time of recombination, as well as accurate UV observations (e.g., with ULTRASAT), will help break the extinction/radius degeneracy and independently determine both.

Journal ArticleDOI
Claudia P. Gutiérrez1, Mark Sullivan1, L. Martinez2, L. Martinez3, Melina C. Bersten4, Melina C. Bersten3, Melina C. Bersten2, Cosimo Inserra5, Mathew Smith1, Joseph P. Anderson6, Yen-Chen Pan7, A. Pastorello, Lluís Galbany8, Peter Nugent9, C. R. Angus10, Cristina Barbarino11, Daniela Carollo, T. W. Chen12, Tamara M. Davis13, M. Della Valle6, Ryan J. Foley14, Morgan Fraser15, C. Frohmaier16, Santiago González-Gaitán17, Mariusz Gromadzki18, Erkki Kankare19, R. Kokotanekova6, Juna A. Kollmeier20, Geraint F. Lewis21, M. R. Magee22, Kate Maguire22, Anais Möller, Nidia Morrell20, Matt Nicholl23, M. Pursiainen1, Jesper Sollerman11, N. E. Sommer24, E. Swann16, B. E. Tucker24, P. Wiseman1, Michel Aguena25, S. Allam26, Santiago Avila27, E. Bertin28, E. Bertin29, David Brooks30, E. Buckley-Geer26, D. L. Burke31, A. Carnero Rosell, M. Carrasco Kind32, J. Carretero, M. Costanzi33, L. N. da Costa, J. De Vicente, S. Desai34, H. T. Diehl26, P. Doel30, T. F. Eifler35, T. F. Eifler36, B. Flaugher26, Pablo Fosalba37, Josh Frieman26, Juan Garcia-Bellido27, D. W. Gerdes38, Daniel Gruen31, Robert A. Gruendl32, J. Gschwend, G. Gutierrez26, Samuel Hinton13, D. L. Hollowood14, K. Honscheid39, David J. James40, Kyler Kuehn41, Kyler Kuehn42, N. Kuropatkin26, Ofer Lahav30, Marcos Lima25, M. A. G. Maia, M. March43, Felipe Menanteau32, Ramon Miquel, Eric Morganson32, Antonella Palmese26, F. Paz-Chinchón32, A. A. Plazas44, M. Sako43, E. J. Sanchez, V. Scarpine26, Michael Schubnell38, S. Serrano37, I. Sevilla-Noarbe, Marcelle Soares-Santos45, E. Suchyta46, M. E. C. Swanson32, Gregory Tarle38, Daniel Thomas16, T. N. Varga12, T. N. Varga47, A. R. Walker, R. D. Wilkinson48 
TL;DR: DES16C3cje as mentioned in this paper is a unique type II supernova with very narrow photospheric lines corresponding to very low expansion velocities of ≲1500 km/s−1, and the light curve shows an initial peak that fades after 50-d before slowly rebrightening over a further 100-d to reach an absolute brightness of −15.5
Abstract: We present DES16C3cje, a low-luminosity, long-lived type II supernova (SN II) at redshift 0.0618, detected by the Dark Energy Survey (DES). DES16C3cje is a unique SN. The spectra are characterized by extremely narrow photospheric lines corresponding to very low expansion velocities of ≲1500 km s−1, and the light curve shows an initial peak that fades after 50 d before slowly rebrightening over a further 100 d to reach an absolute brightness of Mr ∼ −15.5 mag. The decline rate of the late-time light curve is then slower than that expected from the powering by radioactive decay of 56Co, but is comparable to that expected from accretion power. Comparing the bolometric light curve with hydrodynamical models, we find that DES16C3cje can be explained by either (i) a low explosion energy (0.11 foe) and relatively large 56Ni production of 0.075 M⊙ from an ∼15 M⊙ red supergiant progenitor typical of other SNe II, or (ii) a relatively compact ∼40 M⊙ star, explosion energy of 1 foe, and 0.08 M⊙ of 56Ni. Both scenarios require additional energy input to explain the late-time light curve, which is consistent with fallback accretion at a rate of ∼0.5 × 10−8 M⊙ s−1.

Journal ArticleDOI
TL;DR: In this article, a survey of the early evolution of 12 Type IIn supernovae (SNe IIn) in the Ultra-Violet (UV) and visible light is presented.
Abstract: We present a survey of the early evolution of 12 Type IIn supernovae (SNe IIn) in the Ultra-Violet (UV) and visible light. We use this survey to constrain the geometry of the circumstellar material (CSM) surrounding SN IIn explosions, which may shed light on their progenitor diversity. In order to distinguish between aspherical and spherical circumstellar material (CSM), we estimate the blackbody radius temporal evolution of the SNe IIn of our sample, following the method introduced by Soumagnac et al. We find that higher luminosity objects tend to show evidence for aspherical CSM. Depending on whether this correlation is due to physical reasons or to some selection bias, we derive a lower limit between 35% and 66% on the fraction of SNe IIn showing evidence for aspherical CSM. This result suggests that asphericity of the CSM surrounding SNe IIn is common - consistent with data from resolved images of stars undergoing considerable mass loss. It should be taken into account for more realistic modelling of these events.

Journal ArticleDOI
TL;DR: In this article, the authors presented a catalogue of over 10 million variable source candidates found in Data Release 1 (DR1) of the Zwicky Transient Facility (ZTF).
Abstract: Author(s): Ofek, Eran O; Soumagnac, Maayane; Nir, Guy; Gal-Yam, Avishay; Nugent, Peter; Masci, Frank; Kulkarni, Shri R | Abstract: ABSTRACT Variable sources probe a wide range of astrophysical phenomena. We present a catalogue of over 10 million variable source candidates found in Data Release 1 (DR1) of the Zwicky Transient Facility (ZTF). We perform a periodicity search up to a frequency of 160 d−1, and we classify the light curves into erratic and smooth variables. We also present variability indicators and the results of a periodicity search, up to a frequency of 5 d−1, for about 1 billion sources in the ZTF-DR1 light curve data base. We present several new short-period (l90 min) candidates, and about 60 new dwarf nova candidates, including two candidate eclipsing systems. Both the 10 million variables catalogue and ∼1 billion source catalogue are available online in catsHTM format.

Posted Content
TL;DR: In this paper, the authors describe the advantage of a global multi-telescope network towards this end, with a particular focus on the key and complementary role the DECam plays in multi-facility follow-up.
Abstract: Synoptic searches for the optical counterpart to a binary neutron star (BNS) or neutron star-black hole (NSBH) merger can pose significant challenges towards the discovery of kilonovae and performing multi-messenger science. In this work, we describe the advantage of a global multi-telescope network towards this end, with a particular focus on the key and complementary role the Dark Energy Camera (DECam) plays in multi-facility follow-up. We describe the Global Relay of Observatories Watching Transients Happen (GROWTH) Target-of-Opportunity (ToO) Marshal, a common web application we built to ingest events, plan observations, search for transient candidates, and retrieve performance summary statistics for all of the telescopes in our network. Our infrastructure enabled us to conduct observations of two events during O3a, S190426c and S190510g. Furthermore, our analysis of deep DECam observations of S190814bv conducted by the DESGW team, and access to a variety of global follow-up facilities allowed us to place meaningful constraints on the parameters of the kilonova and the merging binary. We emphasize the importance of a global telescope network in conjunction with a power telescope like DECam in performing searches for the counterparts to gravitational-wave sources.

Journal ArticleDOI
M. Pursiainen1, Claudia P. Gutiérrez1, P. Wiseman1, M. Childress1, Mathew Smith1, C. Frohmaier2, C. Angus1, N. Castro Segura1, L. Kelsey1, Mark Sullivan1, Lluís Galbany3, Peter Nugent4, Bruce A. Bassett5, D. J. Brout6, Daniela Carollo7, C. B. D'Andrea6, Tamara M. Davis8, Ryan J. Foley9, M. Grayling1, Samuel Hinton8, Cosimo Inserra10, Richard Kessler11, Geraint F. Lewis12, C. Lidman13, Edward Macaulay2, M. March6, Anais Möller14, T. Muller1, Daniel Scolnic15, N. E. Sommer13, E. Swann2, B. P. Thomas16, B. E. Tucker13, M. Vincenzi2, T. M. C. Abbott, S. Allam17, J. Annis17, Santiago Avila18, E. Bertin19, David Brooks20, E. Buckley-Geer17, D. L. Burke21, D. L. Burke22, A. Carnero Rosell, M. Carrasco Kind23, M. Carrasco Kind24, L. N. da Costa, J. De Vicente, S. Desai25, H. T. Diehl17, P. Doel20, T. F. Eifler26, T. F. Eifler27, S. Everett9, B. Flaugher17, Josh Frieman11, Josh Frieman17, Juan Garcia-Bellido18, Enrique Gaztanaga28, D. W. Gerdes29, Daniel Gruen22, Daniel Gruen21, Robert A. Gruendl24, Robert A. Gruendl23, J. Gschwend, G. Gutierrez17, D. L. Hollowood9, K. Honscheid30, David J. James31, A. G. Kim4, Elisabeth Krause26, Kyler Kuehn32, Kyler Kuehn33, M. A. G. Maia, Jennifer L. Marshall34, Felipe Menanteau23, Felipe Menanteau24, Ramon Miquel35, Ramon Miquel36, R. L. C. Ogando, Antonella Palmese11, Antonella Palmese17, F. Paz-Chinchón24, F. Paz-Chinchón23, A. A. Plazas37, A. Roodman21, A. Roodman22, E. J. Sanchez, V. Scarpine17, Michael Schubnell29, S. Serrano28, I. Sevilla-Noarbe, E. Suchyta38, M. E. C. Swanson23, Gregory Tarle29, W. C. Wester17 
TL;DR: In this article, the authors present an analysis of DES17X1boj and DES16E2bjy, two peculiar transients discovered by the DES, which exhibit nearly identical double-peaked light curves that reach very different maximum luminosities (Mr = −15.4 and −17.9, respectively).
Abstract: We present an analysis of DES17X1boj and DES16E2bjy, two peculiar transients discovered by the Dark Energy Survey (DES). They exhibit nearly identical double-peaked light curves that reach very different maximum luminosities (Mr = −15.4 and −17.9, respectively). The light-curve evolution of these events is highly atypical and has not been reported before. The transients are found in different host environments: DES17X1boj was found near the nucleus of a spiral galaxy, while DES16E2bjy is located in the outskirts of a passive red galaxy. Early photometric data are well fitted with a blackbody and the resulting moderate photospheric expansion velocities (1800 km s−1 for DES17X1boj and 4800 km s−1 for DES16E2bjy) suggest an explosive or eruptive origin. Additionally, a feature identified as high-velocity Ca II absorption (⁠v ≈ 9400 km s−1) in the near-peak spectrum of DES17X1boj may imply that it is a supernova. While similar light-curve evolution suggests a similar physical origin for these two transients, we are not able to identify or characterize the progenitors.

Journal ArticleDOI
TL;DR: It is demonstrated that the tiling and dynamic observing strategies jointly result in a more uniform-depth survey that has higher efficiency for a given total observing time compared with the traditional approach of using fixed exposure times.
Abstract: The Legacy Surveys, a combination of three ground-based imaging surveys, have mapped 16,000 deg$^2$ in three optical bands ($g$, $r$, and $z$) to a depth 1--$2$~mag deeper than the Sloan Digital Sky Survey (SDSS). Our work addresses one of the major challenges of wide-field imaging surveys conducted at ground-based observatories: the varying depth that results from varying observing conditions at Earth-bound sites. To mitigate these effects, two of the Legacy Surveys (the Dark Energy Camera Legacy Survey, or DECaLS; and the Mayall $z$-band Legacy Survey, or MzLS) employed a unique strategy to dynamically adjust the exposure times as rapidly as possible in response to the changing observing conditions. We present the tiling and observing strategies used by these surveys. We demonstrate that the tiling and dynamic observing strategies jointly result in a more uniform-depth survey that has higher efficiency for a given total observing time compared with the traditional approach of using fixed exposure times.

Journal ArticleDOI
TL;DR: The Dark Energy Spectroscopic Instrument Legacy Survey (DECaLS) as discussed by the authors is a combination of three ground-based imaging surveys, which have mapped 16,000 deg2 in three optical bands (g, r, and z) to a depth 1-2 mag deeper than the Sloan Digital Sky Survey.
Abstract: Author(s): Burleigh, KJ; Landriau, M; Dey, A; Lang, D; Schlegel, DJ; Nugent, PE; Blum, R; Findlay, JR; Finkbeiner, DP; Herrera, D; Honscheid, K; Juneau, S; Mcgreer, I; Meisner, AM; Moustakas, J; Myers, AD; Patej, A; Schlafly, EF; Valdes, F; Walker, AR; Weaver, BA; Yeche, C | Abstract: The Dark Energy Spectroscopic Instrument Legacy Surveys, a combination of three ground-based imaging surveys, have mapped 16,000 deg2 in three optical bands (g, r, and z) to a depth 1-2 mag deeper than the Sloan Digital Sky Survey. Our work addresses one of the major challenges of wide-field imaging surveys conducted at ground-based observatories: the varying depth that results from varying observing conditions at Earth-bound sites. To mitigate these effects, the Legacy Surveys (the Dark Energy Camera Legacy Survey, or DECaLS; the Mayall z-band Legacy Survey, or MzLS; and the Beiijing-Arizona Sky Survey, or BASS) employed a unique strategy to dynamically adjust the exposure times as rapidly as possible in response to the changing observing conditions. We present the tiling and observing strategies used by the first two of these surveys. We demonstrate that the tiling and dynamic observing strategies jointly result in a more uniform-depth survey that has higher efficiency for a given total observing time compared with the traditional approach of using fixed exposure times.

Journal ArticleDOI
TL;DR: In this article, the authors present a survey of the early evolution of 12 Type IIn supernovae at ultraviolet and visible light wavelengths, and use this survey to constrain the geometry of the circumstellar material (CSM) surrounding SN IIn explosions, which may shed light on their progenitor diversity.
Abstract: We present a survey of the early evolution of 12 Type IIn supernovae (SNe IIn) at ultraviolet and visible light wavelengths. We use this survey to constrain the geometry of the circumstellar material (CSM) surrounding SN IIn explosions, which may shed light on their progenitor diversity. In order to distinguish between aspherical and spherical CSM, we estimate the blackbody radius temporal evolution of the SNe IIn of our sample, following the method introduced by Soumagnac et al. We find that higher-luminosity objects tend to show evidence for aspherical CSM. Depending on whether this correlation is due to physical reasons or to some selection bias, we derive a lower limit between 35% and 66% for the fraction of SNe IIn showing evidence for aspherical CSM. This result suggests that asphericity of the CSM surrounding SNe IIn is common—consistent with data from resolved images of stars undergoing considerable mass loss. It should be taken into account for more realistic modeling of these events.

Journal ArticleDOI
TL;DR: In this article, Harris et al. simulate one-dimensional hydrodynamics of SNe Ia and Ib impacting 300 unique CSM configurations using RT1D, which captures the Rayleigh-Taylor instability.
Abstract: Author(s): Harris, CE; Nugent, PE | Abstract: Explaining the observed diversity of supernovae (SNe) and the physics of explosion requires knowledge of their progenitor stars, which can be obtained by constraining the circumstellar medium (CSM). Models of the SN ejecta colliding with the CSM are necessary to infer the structure of the CSM and tie it back to a progenitor model. Recent SNe I revealed CSM concentrated at a distance r ∼ 1016 cm, for which models of SN interaction are extremely limited. In this paper, we assume the concentrated region is a "wall" representing swept-up material, and unswept material lies outside the wall. We simulate one-dimensional hydrodynamics of SNe Ia and Ib impacting 300 unique CSM configurations using RT1D, which captures the Rayleigh-Taylor instability. We find that the density ratio between the wall and ejecta-denoted A 0 or "wall height"-is key, and higher walls deviate more from self-similar evolution. Functional fits accounting for A 0 are presented for the forward-shock radius evolution. We show that higher walls have more degeneracy between CSM properties in the deceleration parameter, slower shocks, deeper-probing reverse shocks, slower shocked ejecta, less ejecta mass than CSM in the shock, and more mixing of ejecta into the CSM at early times. We analyze observations of SN 2014C (Type Ib) and suggest that it had a moderately high wall (10 ≲ A 0 ≲ 200) and wind-like outer CSM. We also postulate an alternate interpretation for the radio data of SN 2014C, that the radio rise occurs in the wind rather than the wall. Finally, we find that hydrodynamic measurements at very late times cannot distinguish the presence of a wall, except perhaps as an anomalously wide shock region.

Journal ArticleDOI
TL;DR: The Zwicky Transient Facility (ZTF) is an optical time-domain survey that observes the entire northern sky every few nights including the Galactic plane and can significantly contribute to the observed microlensing population.
Abstract: Microlensing surveys have discovered thousands of events with almost all events discovered within the Galactic bulge or toward the Magellanic clouds. The Zwicky Transient Facility (ZTF), while not designed to be a microlensing campaign, is an optical time-domain survey that observes the entire northern sky every few nights including the Galactic plane. ZTF observes $\sim10^9$ stars in g-band and r-band and can significantly contribute to the observed microlensing population. We predict that ZTF will observe $\sim$1100 microlensing events in three years of observing within $10^\circ$ degrees latitude of the Galactic plane, with $\sim$500 events in the outer Galaxy ($\ell \geq 10^\circ$). This yield increases to $\sim$1400 ($\sim$800) events by combining every three ZTF exposures, $\sim$1800 ($\sim$900) events if ZTF observes for a total of five years, and $\sim$2400 ($\sim$1300) events for a five year survey with post-processing image stacking. Using the microlensing modeling software PopSyCLE, we compare the microlensing populations in the Galactic bulge and the outer Galaxy. We also present an analysis of the microlensing event ZTF18abhxjmj to demonstrate how to leverage these population statistics in event modeling. ZTF will constrain Galactic structure, stellar populations, and primordial black holes through photometric microlensing.

Proceedings ArticleDOI
01 May 2020
TL;DR: A machine learning strategy is proposed for quickly identifying astronomical transients from synoptic surveys and its effectiveness is demonstrated using a set of timing measurements from the intermediate Palomar Transient Factory (iPTF) workflow.
Abstract: Quickly identifying astronomical transients from synoptic surveys is critical to many recent astrophysical discoveries. However, each of the data processing pipelines in these surveys contains dozens of stages with highly varying time and space requirements. Properly predicting the resources required to run these pipelines is critical for the allocation of computing resources and reducing the discovery response time. We propose a machine learning strategy for this prediction task and demonstrate its effectiveness using a set of timing measurements from the intermediate Palomar Transient Factory (iPTF) workflow. The proposed model utilizes the spatiotemporal correlation of astronomical images, where nearby patches of the sky (space) are likely to have a similar number of objects of interest and workflows executed in the recent past (time) are likely to use a similar amount of time because the machines and data storage systems are likely to be in similar states. We capture the relationship among these spatial and temporal features in a Bayesian network and study how they impact the prediction accuracy. This Bayesian network helps us to identify the most influential features for predictions. With proper features, our models achieve errors close to the random variance boundary within batches of images taken at the same time, which can be regarded as the intrinsic limit of prediction accuracy.

Posted Content
TL;DR: In this paper, the authors used forward modeling with the Tractor to search for an offset AGN in a sample of 5493 optically variable AGN detected with the Zwicky Transient Facility (ZTF).
Abstract: A supermassive black hole (SMBH) ejected from the potential well of its host galaxy via gravitational wave recoil carries important information about the mass ratio and spin alignment of the pre-merger SMBH binary. Such a recoiling SMBH may be detectable as an active galactic nucleus (AGN) broad line region offset by up to 10\,kpc from a disturbed host galaxy. We describe a novel methodology using forward modeling with \texttt{The Tractor} to search for such offset AGN in a sample of 5493 optically variable AGN detected with the Zwicky Transient Facility (ZTF). We present the discovery of 9 AGN which may be spatially offset from their host galaxies and are candidates for recoiling SMBHs. Five of these offset AGN exhibit double-peaked broad Balmer emission from an unobscured accretion disk and four show radio emission indicative of a relativistic jet. The fraction of double-peaked emitters in our spatially offset AGN sample is significantly larger than the 16\% double-peaked emitter fraction observed for ZTF AGN overall. In our sample of variable AGN we also identified 52 merging galaxies, including a new spectroscopically confirmed dual AGN. Finally, we detected the dramatic rebrightening of SDSS1133, a previously discovered variable object and recoiling SMBH candidate, in ZTF. The flare was accompanied by the re-emergence of strong P-Cygni line features indicating it likely is an outbursting luminous blue variable star.

Posted Content
TL;DR: The Type Ia supernova LSQ14fmg exhibits exaggerated properties which may help to reveal the origin of the "super-Chandrasekhar" (or 03fg-like) group.
Abstract: The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties which may help to reveal the origin of the "super-Chandrasekhar" (or 03fg-like) group. The optical spectrum is typical of a 03fg-like SN Ia, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At -23 rest-frame days relative to B-band maximum, LSQ14fmg is already brighter than $M_V$=-19 mag before host extinction correction. The observed color curves show a flat evolution from the earliest observation to approximately one week after maximum. The near-infrared light curves peak brighter than -20.5 mag in the J and H bands, far more luminous than any 03fg-like SNe Ia with near-infrared observations. At one month past maximum, the optical light curves decline rapidly. The early, slow rise and flat color evolution are interpreted to result from an additional excess flux from a power source other than the radioactive decay of the synthesized $^{56}Ni$. The excess flux matches the interaction with a typical superwind of an asymptotic giant branch (AGB) star in density structure, mass-loss rate, and duration. The rapid decline starting at around one month past B-band maximum may be an indication of rapid cooling by active carbon monoxide (CO) formation, which requires a low temperature and high density environment. These peculiarities point to an AGB progenitor near the end of its evolution and the core degenerate scenario as the likely explosion mechanism for LSQ14fmg.

Posted Content
TL;DR: In this paper, the authors used a Monte Carlo simulation of hundreds of millions of SN light curve realizations coupled with the detailed PTF survey detection efficiencies to forward-model the SN rates in PTF.
Abstract: We present measurements of the local core collapse supernova (SN) rate using SN discoveries from the Palomar Transient Factory (PTF). We use a Monte Carlo simulation of hundreds of millions of SN light curve realizations coupled with the detailed PTF survey detection efficiencies to forward-model the SN rates in PTF. Using a sample of 86 core collapse SNe, including 26 stripped-envelope SNe (SESNe), we show that the overall core collapse SN volumetric rate is $r^\mathrm{CC}_v=9.10_{-1.27}^{+1.56}\times10^{-5}\,\text{SNe yr}^{-1}\,\text{Mpc}^{-3}\, h_{70}^{3}$ at $ \langle z \rangle = 0.028$, and the SESN volumetric rate is $r^\mathrm{SE}_v=2.41_{-0.64}^{+0.81}\times10^{-5}\, \text{SNe yr}^{-1}\,\text{Mpc}^{-3}\, h_{70}^{3}$. We further measure a volumetric rate for hydrogen-free superluminous SNe (SLSNe-I) using 8 events at $z{\le}0.2$ of $r^\mathrm{SLSN-I}_v=35_{-13}^{+25}\, \text{SNe yr}^{-1}\text{Gpc}^{-3}\, h_{70}^{3}$, which represents the most precise SLSN-I rate measurement to date. Using a simple cosmic star-formation history to adjust these volumetric rate measurements to the same redshift, we measure a local ratio of SLSN-I to SESN of $\sim1/810^{+1500}_{-94}$, and of SLSN-I to all CCSN types of $\sim 1/3500^{+2800}_{-720}$. However, using host galaxy stellar mass as a proxy for metallicity, we also show that this ratio is strongly metallicity dependent: in low-mass ($\mathrm{log} M_{*} < 9.5 \mathrm{M}_\odot$) galaxies, which are the only environments that host SLSN-I in our sample, we measure a SLSN-I to SESN fraction of $1/300^{+380}_{-170}$ and $1/1700^{+1800}_{-720}$ for all CCSN. We further investigate the SN rates a function of host galaxy stellar mass and show that the specific rates of all core collapse SNe decrease with increasing stellar mass.