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A carbon/oxygen-dominated atmosphere days after explosion for the "super-Chandrasekhar" type Ia SN 2020esm

A carbon/oxygen-dominated atmosphere days after explosion for the "super-Chandrasekhar" type Ia SN 2020esm
A carbon/oxygen-dominated atmosphere days after explosion for the "super-Chandrasekhar" type Ia SN 2020esm

Seeing pristine material from the donor star in a type Ia supernova (SN Ia) explosion can reveal the nature of the binary system. In this paper, we present photometric and spectroscopic observations of SN 2020esm, one of the best-studied SNe of the class of "super-Chandrasekhar" SNe Ia (SC SNe Ia), with data obtained 12 to +360 days relative to peak brightness, obtained from a variety of ground- and space-based telescopes. Initially misclassified as a type II supernova, SN 2020esm peaked at M-B = -19.9 mag, declined slowly (Delta m(15)(B) = 0.92 mag), and had particularly blue UV and optical colors at early times. Photometrically and spectroscopically, SN 2020esm evolved similarly to other SC SNe Ia, showing the usual low ejecta velocities, weak intermediate-mass elements, and the enhanced fading at late times, but its early spectra are unique. Our first few spectra (corresponding to a phase of greater than or similar to 10 days before peak) reveal a nearly pure carbon/oxygen atmosphere during the first days after explosion. This composition can only be produced by pristine material, relatively unaffected by nuclear burning. The lack of H and He may further indicate that SN 2020esm is the outcome of the merger of two carbon/oxygen white dwarfs. Modeling its bolometric light curve, we find an Ni-56 mass of 1.23(-0.14)(+0.14) M-circle dot and an ejecta mass of 1.75(-0.20)(+0.32)M(circle dot), in excess of the Chandrasekhar mass. Finally, we discuss possible progenitor systems and explosion mechanisms of SN 2020esm and, in general, the SC SNe Ia class.

0004-637X
Dimitriadis, Georgios
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Foley, Ryan J.
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Arendse, Nikki
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Coulter, David A.
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Jacobson-Galan, Wynn
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Siebert, Matthew R.
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Izzo, Luca
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Jones, David O.
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Kilpatrick, Charles D.
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Pan, Yen-Chen
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Taggart, Kirsty
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Auchettl, Katie
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Gall, Christa
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Hjorth, Jens
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Kasen, Daniel
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Piro, Anthony L.
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Raimundo, Sandra
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Ramirez-Ruiz, Enrico
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Rest, Armin
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Swift, Jonathan J.
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Woosley, Stan E.
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Dimitriadis, Georgios
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Foley, Ryan J.
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Arendse, Nikki
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Coulter, David A.
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Jacobson-Galan, Wynn
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Siebert, Matthew R.
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Izzo, Luca
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Jones, David O.
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Kilpatrick, Charles D.
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Pan, Yen-Chen
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Taggart, Kirsty
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Auchettl, Katie
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Gall, Christa
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Hjorth, Jens
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Kasen, Daniel
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Piro, Anthony L.
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Raimundo, Sandra
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Ramirez-Ruiz, Enrico
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Rest, Armin
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Swift, Jonathan J.
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Woosley, Stan E.
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Dimitriadis, Georgios, Foley, Ryan J., Arendse, Nikki, Coulter, David A., Jacobson-Galan, Wynn, Siebert, Matthew R., Izzo, Luca, Jones, David O., Kilpatrick, Charles D., Pan, Yen-Chen, Taggart, Kirsty, Auchettl, Katie, Gall, Christa, Hjorth, Jens, Kasen, Daniel, Piro, Anthony L., Raimundo, Sandra, Ramirez-Ruiz, Enrico, Rest, Armin, Swift, Jonathan J. and Woosley, Stan E. (2022) A carbon/oxygen-dominated atmosphere days after explosion for the "super-Chandrasekhar" type Ia SN 2020esm. Astrophysical Journal, 927 (1), [78]. (doi:10.3847/1538-4357/ac4780).

Record type: Article

Abstract

Seeing pristine material from the donor star in a type Ia supernova (SN Ia) explosion can reveal the nature of the binary system. In this paper, we present photometric and spectroscopic observations of SN 2020esm, one of the best-studied SNe of the class of "super-Chandrasekhar" SNe Ia (SC SNe Ia), with data obtained 12 to +360 days relative to peak brightness, obtained from a variety of ground- and space-based telescopes. Initially misclassified as a type II supernova, SN 2020esm peaked at M-B = -19.9 mag, declined slowly (Delta m(15)(B) = 0.92 mag), and had particularly blue UV and optical colors at early times. Photometrically and spectroscopically, SN 2020esm evolved similarly to other SC SNe Ia, showing the usual low ejecta velocities, weak intermediate-mass elements, and the enhanced fading at late times, but its early spectra are unique. Our first few spectra (corresponding to a phase of greater than or similar to 10 days before peak) reveal a nearly pure carbon/oxygen atmosphere during the first days after explosion. This composition can only be produced by pristine material, relatively unaffected by nuclear burning. The lack of H and He may further indicate that SN 2020esm is the outcome of the merger of two carbon/oxygen white dwarfs. Modeling its bolometric light curve, we find an Ni-56 mass of 1.23(-0.14)(+0.14) M-circle dot and an ejecta mass of 1.75(-0.20)(+0.32)M(circle dot), in excess of the Chandrasekhar mass. Finally, we discuss possible progenitor systems and explosion mechanisms of SN 2020esm and, in general, the SC SNe Ia class.

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Accepted/In Press date: 20 December 2021
Published date: 1 March 2022
Additional Information: Funding Information: The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. Funding Information: This work was supported by a VILLUM FONDEN Investigator grant to J.H. (project No. 16599) and by a VILLUM FONDEN Young Investigator grant to C.G. (project No. 25501). Funding Information: A major upgrade of the Kast spectrograph on the Shane 3 m telescope at Lick Observatory was made possible through generous gifts from the Heising-Simons Foundation as well as William and Marina Kast. Research at Lick Observatory is partially supported by a generous gift from Google. Funding Information: W.J.-G. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1842165 and the IDEAS Fellowship Program at Northwestern University. W.J.-G. acknowledges support through NASA grants in support of Hubble Space Telescope program GO-16075. Funding Information: M.R.S. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. 1842400. Funding Information: The UCSC transient team is supported in part by NSF grant AST-1518052, NASA/Swift grant 80NSSC19K1386, the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, and by a fellowship from the David and Lucile Packard Foundation to R.J.F. Funding Information: D.A.C. acknowledges support from the National Science Foundation Graduate Research Fellowship under grant DGE1339067. Funding Information: Based on observations obtained at the international Gemini Observatory (NOIRLab Prop. ID 2020B-0358 and GN-2021A-DD-102), a program of NSF’s NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). We thank the director, J. Lotz, and J. Blakeslee for their approval of and assistance with our DD program. Funding Information: This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program SNAP-16239. Funding Information: We acknowledge the use of public data from the Neil Gehrels Swift Observatory data archive. The work made use of Swift/UVOT data reduced by P. J. Brown and released in the Swift Optical/Ultraviolet Supernova Archive (SOUSA). SOUSA is supported by NASA’s Astrophysics Data Analysis Program through grant NNX13AF35G. Funding Information: Support for D.O.J. was provided by NASA through the NASA Hubble Fellowship grant HF2-51462.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Funding Information: Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have had the opportunity to conduct observations from this mountain. Funding Information: This publication has made use of data collected at Lulin Observatory, partly supported by MoST grant 108-2112-M-008-001. Funding Information: The Young Supernova Experiment and its research infrastructure is supported by the European Research Council under the European Union’s Horizon 2020 research and innovation program (ERC grant agreement No. 101002652, PI K. Mandel), the Heising-Simons Foundation (2018-0913, PI R. Foley; 2018-0911, PI R. Margutti), NASA (NNG17PX03C, PI R. Foley), NSF (AST-1720756, AST-1815935, PI R. Foley; AST-1909796, AST-1944985, PI R. Margutti), the David & Lucille Packard Foundation (PI R. Foley), VILLUM FONDEN (project number 16599, PI J. Hjorth), and the Center for AstroPhysical Surveys (CAPS) at the National Center for Supercomputing Applications (NCSA) and the University of Illinois Urbana-Champaign. Publisher Copyright: © 2022. The Author(s). Published by the American Astronomical Society.

Identifiers

Local EPrints ID: 472098
URI: http://eprints.soton.ac.uk/id/eprint/472098
ISSN: 0004-637X
PURE UUID: 78befd1b-a45a-48d6-be65-1fc81b9cb5b3
ORCID for Sandra Raimundo: ORCID iD orcid.org/0000-0002-6248-398X

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Date deposited: 25 Nov 2022 17:41
Last modified: 19 Jan 2023 02:56

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Contributors

Author: Georgios Dimitriadis
Author: Ryan J. Foley
Author: Nikki Arendse
Author: David A. Coulter
Author: Wynn Jacobson-Galan
Author: Matthew R. Siebert
Author: Luca Izzo
Author: David O. Jones
Author: Charles D. Kilpatrick
Author: Yen-Chen Pan
Author: Kirsty Taggart
Author: Katie Auchettl
Author: Christa Gall
Author: Jens Hjorth
Author: Daniel Kasen
Author: Anthony L. Piro
Author: Sandra Raimundo ORCID iD
Author: Enrico Ramirez-Ruiz
Author: Armin Rest
Author: Jonathan J. Swift
Author: Stan E. Woosley

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