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ZTF Early Observations of Type Ia Supernovae. II. First Light, the Initial Rise, and Time to Reach Maximum Brightness

Miller, A. A. and Yao, Y. and Bulla, M. and Pankow, C. and Bellm, E. C. and Cenko, S. B. and Dekany, R. and Fremling, C. and Graham, M. J. and Kupfer, T. and Laher, R. R. and Mahabal, A. A. and Masci, F. J. and Nugent, P. E. and Riddle, R. and Rusholme, B. and Smith, R. M. and Shupe, D. L. and van Roestel, J. and Kulkarni, S. R. (2020) ZTF Early Observations of Type Ia Supernovae. II. First Light, the Initial Rise, and Time to Reach Maximum Brightness. Astrophysical Journal, 902 (1). Art. No. 47. ISSN 1538-4357. doi:10.3847/1538-4357/abb13b.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Miller, A. A.0000-0001-9515-478X
Bulla, M.0000-0002-8255-5127
Pankow, C.0000-0002-1128-3662
Bellm, E. C.0000-0001-8018-5348
Cenko, S. B.0000-0003-1673-970X
Dekany, R.0000-0002-5884-7867
Fremling, C.0000-0002-4223-103X
Graham, M. J.0000-0002-3168-0139
Kupfer, T.0000-0002-6540-1484
Laher, R. R.0000-0003-2451-5482
Mahabal, A. A.0000-0003-2242-0244
Masci, F. J.0000-0002-8532-9395
Nugent, P. E.0000-0002-3389-0586
Riddle, R.0000-0002-0387-370X
Rusholme, B.0000-0001-7648-4142
Smith, R. M.0000-0001-7062-9726
Shupe, D. L.0000-0003-4401-0430
van Roestel, J.0000-0002-2626-2872
Kulkarni, S. R.0000-0001-5390-8563
Additional Information:© 2020 The American Astronomical Society. Received 2020 January 17; revised 2020 August 4; accepted 2020 August 6; published 2020 October 9. The authors would like to thank the anonymous referee for helpful comments that have improved this paper. We thank M. Magee for sharing details about the rise times of SNe Ia models. A. A. M. would like to thank E. A. Chase, M. Zevin, and C. P. L. Berry for useful discussions on KDEs and PDFs. We also appreciate D. Goldstein's suggestions regarding SALT2 as a proxy for rise time. Y. Yang, J. Nordin, R. Biswas, and J. Sollerman provided detailed comments on an early draft that improved this manuscript. A. A. M. is funded by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship Program; he also receives support as a CIERA Fellow by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). Y. Y., U. C. F., and S. R. K. thank the Heising-Simons Foundation for supporting ZTF research (#2018-0907). This research was supported in part through the computational resources and staff contributions provided for the Quest high-performance computing facility at Northwestern University, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology. This work was supported in part by the GROWTH project funded by the National Science Foundation under grant No. 1545949. This work is based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. Software: astropy (Astropy Collaboration et al. 2013), scipy (Virtanen et al. 2020), matplotlib (Hunter 2007), pandas (McKinney 2010), emcee (Foreman-Mackey et al. 2013), corner (Foreman-Mackey 2016), SALT2 (Guy et al. 2007), sncosmo (Barbary et al. 2016), statsmodels (Seabold & Perktold 2010).
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
Large Synoptic Survey Telescope CorporationUNSPECIFIED
Brinson FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)UNSPECIFIED
Northwestern UniversityUNSPECIFIED
Heising-Simons Foundation2018-0907
ZTF partner institutionsUNSPECIFIED
Subject Keywords:Type Ia supernovae ; Surveys ; Catalogs ; Observational astronomy ; Supernovae
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Type Ia supernovae (1728); Surveys (1671); Catalogs (205); Observational astronomy (1145); Supernovae (1668)
Record Number:CaltechAUTHORS:20200413-154440794
Persistent URL:
Official Citation:A. A. Miller et al 2020 ApJ 902 47
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102513
Deposited By: Tony Diaz
Deposited On:13 Apr 2020 23:00
Last Modified:16 Nov 2021 18:12

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