SN 2023xwi: Forbidden line emission in the peak spectrum of a Ca-strong transient

: Touchard-Paxton, C. -G.; Frohmaier, C.; Pursiainen, M.; Sullivan, M.; Polin, A.; Dimitriadis, G.; Galbany, L.; Killestein, T. L.; Kumar, A.; Lyman, J.

Publisher: Oxford University Press (OUP)

: OXFORD

: 2025

: Monthly Notices of the Royal Astronomical Society

: MON NOT R ASTRON SOC

: 537

: 2

: 1015

: 1027

: 13

: 0035-8711

: 1365-2966

DOI: https://doi.org/10.1093/mnras/staf069

: https://doi.org/10.1093/mnras/staf069

: https://research.utu.fi/converis/portal/detail/Publication/485123711

We present an extensive optical photometric and spectroscopic investigation into the calcium-rich supernova (SN) - SN 2023xwi. Observations from a variety of ground-based telescopes follow the SN from 8 d pre-peak brightness to 87 d post-peak, covering both early-time (photospheric) and late-time (nebular) phases of the SN. Objects of this class are characterized by nebular spectra that are dominated by [Ca II] lambda lambda 7291, 7324 emission. SN 2023xwi displays a unique peculiarity in that its forbidden [Ca ii] feature is visible in its peak photospheric spectrum - far earlier than expected in current models. This is one of the strongest and earliest detections of this feature in Ca-rich SNe in photospheric-phase spectra. We investigate the velocity evolution of this spectral feature and show that it cannot be easily explained by conventional progenitor systems. From our observations, we propose an SN progenitor embedded in an environment polluted by a recurrent He-nova AM CVn system.

staf069.pdf

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We thank Christian Knigge for useful scientific discussions. CF and AP acknowledge support from a Royal Society International Exchanges grant (IES\ R\ 3223075). MP and JL acknowledge support from a UK Research and Innovation Fellowship (MR/T020784/1). LG acknowledges financial support from AGAUR, CSIC, MCIN, and AEI 10.13039/501100011033 under projects PID2023-151307NB-I00, PIE 20215AT016, CEX2020-001058-M, and 2021-SGR-01270. TLK acknowledges support via an Research Council of Finland grant (340613; P.I. R. Kotak), and from the UK Science and Technology Facilities Council (STFC, grant number ST/T506503/1).
Based in part on observations made with the Nordic Optical Telescope (NOT), 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 NOT data presented here were obtained with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOT.
The Gravitational-wave Optical Transient Observer (GOTO) project acknowledges the support of the Monash-Warwick Alliance, University of Warwick, Monash University, University of Sheffield, University of Leicester; Armagh Observatory & Planetarium, the National Astronomical Research Institute of Thailand (NARIT), Instituto de Astrofísica de Canarias (IAC), University of Portsmouth, University of Turku. We acknowledge support from the Science and Technology Facilities Council (STFC, grant numbers ST/T007184/1, ST/T003103/1, ST/T000406/1,ST/X001121/1, and ST/Z000165/1).
This work makes use of observations from the Las Cumbres Observatory Global Telescope network. Time on the Las Cumbres Observatory 1m network was awarded via OPTICON (proposal 23B030).
This work makes use of observations from the Las Cumbres Observatory global telescope network.
Based on observations made with the Liverpool Telescope 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.
This work includes data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. ATLAS is primarily funded to search for near Eearth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; by-products of the NEO search include images and catalogues from the survey area. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen’s University Belfast, the Space Telescope Science Institute, and the South African Astronomical Observatory.
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.