Strong Calcium Emission Indicates that the Ultraviolet-flashing SN Ia 2019yvq Was the Result of a Sub-Chandrasekar-mass Double-detonation Explosion
Abstract
We present nebular spectra of the Type Ia supernova (SN Ia) SN 2019yvq, which had a bright flash of blue and ultraviolet light after exploding, followed by a rise similar to other SNe Ia. Although SN 2019yvq displayed several other rare characteristics, such as persistent high ejecta velocity near peak brightness, it was not especially peculiar, and if the early "excess" emission were not observed, it would likely be included in cosmological samples. The excess flux can be explained by several different physical models linked to the details of the progenitor system and explosion mechanism. Each has unique predictions for the optically thin emission at late times. In our nebular spectra, we detect strong [Ca ii] λλ7291, 7324 and Ca near-IR triplet emission, consistent with a double-detonation explosion. We do not detect H, He, or [O i] emission, predictions for some single-degenerate progenitor systems and violent white dwarf mergers. The amount of swept-up H or He is < 2.8 × 10⁻⁴ and 2.4 × 10⁻⁴ M_⊙, respectively. Aside from strong Ca emission, the SN 2019yvq nebular spectrum is similar to those of typical SNe Ia with the same light-curve shape. Comparing to double-detonation models, we find that the Ca emission is consistent with a model with a total progenitor mass of 1.15 M_⊙. However, we note that a lower progenitor mass better explains the early light-curve and peak luminosity. The unique properties of SN 2019yvq suggest that thick He-shell double detonations only account for 1.1_(-1.1)^(+2.1)% of the total "normal" SN Ia rate. The SN 2019yvq is one of the best examples yet that multiple progenitor channels appear necessary to reproduce the full diversity of "normal" SNe Ia.
Additional Information
© 2020. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2020 July 24; revised 2020 August 7; accepted 2020 August 12; published 2020 September 4. M.R.S. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. 1842400. The UCSC team is supported in part by NASA grant NNG17PX03C, NSF grant AST-1815935, the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, and a fellowship from the David and Lucile Packard Foundation to R.J.F. The Computational HEP program in the Department of Energy's Science Office of High Energy Physics provided resources through grant No. KA2401022. Calculations presented in this paper used the resources of the National Energy Research Scientific Computing Center (NERSC), which is supported by the Office of Science of the U.S. Department of Energy under contract No. DE-AC02-05CH11231. 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. We thank Elena Manjavacas and Lucas Fuhrman for assistance with these observations. 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. Facility: Keck:I (LRIS). - Software: astropy (Astropy Collaboration et al. 2013), kaepora (Siebert et al. 2019), Castro (Almgren et al. 2010), Sedona (Kasen et al. 2006), SedoNeb (Botyánszki & Kasen 2017).Attached Files
Published - Siebert_2020_ApJL_900_L27.pdf
Accepted Version - 2007.13793.pdf
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Additional details
- Eprint ID
- 105338
- Resolver ID
- CaltechAUTHORS:20200911-133135458
- DGE-1842400
- NSF Graduate Research Fellowship
- NNG17PX03C
- NASA
- AST-1815935
- NSF
- Gordon and Betty Moore Foundation
- Heising-Simons Foundation
- David and Lucile Packard Foundation
- KA2401022
- Department of Energy (DOE)
- DE-AC02-05CH11231
- Department of Energy (DOE)
- W. M. Keck Foundation
- Created
-
2020-09-15Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- TAPIR, Walter Burke Institute for Theoretical Physics