SN 2021zny: an early flux excess combined with late-time oxygen emission suggests a double white dwarf merger event

Creators: Dimitriadis, Georgios; Maguire, Kate; Karambelkar, Viraj R.; Lebron, Ryan J.; Liu, Chang; Kozyreva, Alexandra; Miller, Adam A.; Ridden-Harper, Ryan; Anderson, Joseph P.; Chen, Ting-Wan; Coughlin, Michael; Valle, Massimo Della; Drake, Andrew; Galbany, Lluís; Gromadzki, Mariusz; Groom, Steven L.; Gutiérrez, Claudia P.; Ihanec, Nada; Inserra, Cosimo; Johansson, Joel; Müller-Bravo, Tomás E.; Nicholl, Matt; Polin, Abigail; Rusholme, Ben; Schulze, Steve; Sollerman, Jesper; Srivastav, Shubham; Taggart, Kirsty; Wang, Qinan; Yang, Yi; Young, David R.

Abstract

We present a photometric and spectroscopic analysis of the ultraluminous and slowly evolving 03fg-like Type Ia SN 2021zny. Our observational campaign starts from ∼5.3 h after explosion (making SN 2021zny one of the earliest observed members of its class), with dense multiwavelength coverage from a variety of ground- and space-based telescopes, and is concluded with a nebular spectrum ∼10 months after peak brightness. SN 2021zny displayed several characteristics of its class, such as the peak brightness (M_B = −19.95 mag), the slow decline (Δm_(15)(B) = 0.62 mag), the blue early-time colours, the low ejecta velocities, and the presence of significant unburned material above the photosphere. However, a flux excess for the first ∼1.5 d after explosion is observed in four photometric bands, making SN 2021zny the third 03fg-like event with this distinct behaviour, while its +313 d spectrum shows prominent [O ɪ] lines, a very unusual characteristic of thermonuclear SNe. The early flux excess can be explained as the outcome of the interaction of the ejecta with ∼0.04M_⊙ of H/He-poor circumstellar material at a distance of ∼10^(12) cm, while the low ionization state of the late-time spectrum reveals low abundances of stable iron-peak elements. All our observations are in accordance with a progenitor system of two carbon/oxygen white dwarfs that undergo a merger event, with the disrupted white dwarf ejecting carbon-rich circumstellar material prior to the primary white dwarf detonation.

Additional Information

© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) We thank the anonymous referee for helpful comments that improved the clarity and presentation of this Paper. GD and KM are supported by the H2020 European Research Council grant no. 758638. AAM is partially supported by NASA grant no. 80NSSC22K0541. MC acknowledges support from the National Science Foundation with grant numbers PHY-2010970 and OAC-2117997. LG and TEMB acknowledge financial support from the Spanish Ministerio de Ciencia e Innovación (MCIN), the Agencia Estatal de Investigación (AEI) 10.13039/501100011033 under the PID2020-115253GA-I00 HOSTFLOWS project, from Centro Superior de Investigaciones Científicas (CSIC) under the PIE project 20215AT016, and by the programme Unidad de Excelencia María de Maeztu CEX2020-001058-M. LG also acknowledges MCIN, AEI and the European Social Fund (ESF) 'Investing in your future' under the 2019 Ramón y Cajal programme RYC2019-027683-I. MG is supported by the EU Horizon 2020 research and innovation programme under grant agreement no. 101004719. NI is partially supported by the Polish NCN DAINA grant no. 2017/27/L/ST9/03221. MN is supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 948381) and by a Fellowship from the Alan Turing Institute. SS acknowledges support from the GREAT research environment, funded by Vetenskapsrådet, the Swedish Research Council, project number 2016-06012. QW is supported in part by NASA grant 80NSSC22K0494, 80NSSC21K0242, and 80NSSC19K0112. YY is supported by a Bengier–Winslow–Robertson Fellowship. This work was funded by ANID, Millennium Science Initiative, ICN12_009. 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-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum and Northwestern University. Operations are conducted by COO, IPAC, and UW. The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). The SED Machine is based upon work supported by the National Science Foundation under grant no. 1106171. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, as part of ePESSTO+ (the advanced Public ESO Spectroscopic Survey for Transient Objects Survey). ePESSTO + observations were obtained under ESO programme IDs 1103.D-0328, 106.216C, 108.220C (PI: Inserra). The Las Cumbres Observatory data have been obtained via OPTCON proposals (IDs: OPTICON 21B/001 and 22A/004). The OPTICON project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730890. Based on observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOT. 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 the opportunity to conduct observations from this mountain. We acknowledge the use of Weizmann Interactive Supernova Data Repository (WISeREP) maintained by the Weizmann Institute of Science computing centre. This work made use of the Heidelberg Supernova Model Archive (HESMA). DATA AVAILABILITY. The data analysed in this paper are available in the electronic edition and via the Weizmann Interactive Supernova Data Repository (WISeREP).

Attached Files

Published - stad536.pdf

Supplemental Material - stad536_supplemental_files.zip

Files

stad536_supplemental_files.zip

Files (7.7 MB)

Name	Size	Download all
stad536_supplemental_files.zip md5:34101df29c751eb05ab78a8ac6c58746	254.7 kB	Preview Download
stad536.pdf md5:d0216b22148cf350eef73738eaca3b43	7.4 MB	Preview Download

Additional details

Views

Downloads

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes

More info on how stats are collected....

Resource type: Journal Article
Publisher: Royal Astronomical Society
Published in: Monthly Notices of the Royal Astronomical Society, 521(1), 1162-1183, ISSN: 0035-8711.