Discovery of a Double-detonation Thermonuclear Supernova Progenitor

Creators: Kupfer, Thomas; Bauer, Evan B.; van Roestel, Jan; Bellm, Eric C.; Bildsten, Lars; Fuller, Jim; Prince, Thomas A.; Heber, Ulrich; Geier, Stephan; Green, Matthew J.; Kulkarni, Shrinivas R.; Bloemen, Steven; Laher, Russ R.; Rusholme, Ben; Schneider, David

Abstract

We present the discovery of a new double-detonation progenitor system consisting of a hot subdwarf B (sdB) binary with a white dwarf companion with a P_(orb) = 76.34179(2) minutes orbital period. Spectroscopic observations are consistent with an sdB star during helium core burning residing on the extreme horizontal branch. Chimera light curves are dominated by ellipsoidal deformation of the sdB star and a weak eclipse of the companion white dwarf. Combining spectroscopic and light curve fits, we find a low-mass sdB star, M_(sdB) = 0.383 ± 0.028 M_⊙ with a massive white dwarf companion, M_(WD) = 0.725 ± 0.026 M_⊙. From the eclipses we find a blackbody temperature for the white dwarf of 26,800 K resulting in a cooling age of ≈25 Myr whereas our MESA model predicts an sdB age of ≈170 Myr. We conclude that the sdB formed first through stable mass transfer followed by a common envelope which led to the formation of the white dwarf companion ≈25 Myr ago. Using the MESA stellar evolutionary code we find that the sdB star will start mass transfer in ≈6 Myr and in ≈60 Myr the white dwarf will reach a total mass of 0.92 M_⊙ with a thick helium layer of 0.17 M⊙. This will lead to a detonation that will likely destroy the white dwarf in a peculiar thermonuclear supernova. PTF1 J2238+7430 is only the second confirmed candidate for a double-detonation thermonuclear supernova. Using both systems we estimate that at least ≈1% of white dwarf thermonuclear supernovae originate from sdB+WD binaries with thick helium layers, consistent with the small number of observed peculiar thermonuclear explosions.

Additional Information

© 2022. 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 2021 October 23; revised 2022 January 4; accepted 2022 January 5; published 2022 January 27. This research benefited from interactions that were funded by the Gordon and Betty Moore Foundation through grant GBMF5076. This work was supported by the National Science Foundation through grants PHY-1748958 and ACI-1663688. T.K. would like to thank Ylva Götberg for providing the template for Figure 4. T.K. acknowledges support from the National Science Foundation through grant AST #2107982. D.S. was supported by the Deutsche Forschungsgemeinschaft (DFG) under grants HE 1356/70-1 and IR 190/1-1. Observations were obtained with the Samuel Oschin Telescope at the Palomar Observatory as part of the PTF project, a scientific collaboration between the California Institute of Technology, Columbia University, Las Cumbres Observatory, the Lawrence Berkeley National Laboratory, the National Energy Research Scientific Computing Center, the University of Oxford, and the Weizmann Institute of Science. Based on observations obtained with the Samuel Oschin 48 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. 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. Some results presented in this paper are based on observations made with the WHT operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Institutio de Astrofisica de Canarias. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Facilities: PO:1.2 m (PTF) - , PO:1.2 m (ZTF) - , Hale (DBSP) - , ING:Herschel (ISIS) - , Keck:I (HIRES) - , Keck:II (ESI) - , Hale (Chimera) - . Software: Gatspy (Vanderplas 2015; VanderPlas & Ivezić 2015), FITSB2 (Napiwotzki et al. 2004), LCURVE (Copperwheat et al. 2010), emcee (Foreman-Mackey et al. 2013), MESA (Paxton et al. 2011, 2013, 2015, 2018, 2019), Matplotlib (Hunter 2007), Astropy (Astropy Collaboration et al. 2013, 2018), Numpy (Oliphant 2015), ISIS (Houck & Denicola 2000), MAKEE (https://sites.astro.caltech.edu/~tb/makee/).

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