Title: Partly burnt runaway stellar remnants from peculiar thermonuclear supernovae

Abstract

Abstract We report the discovery of three stars that, along with the prototype LP 40−365, form a distinct class of chemically peculiar runaway stars that are the survivors of thermonuclear explosions. Spectroscopy of the four confirmed LP 40−365 stars finds ONe-dominated atmospheres enriched with remarkably similar amounts of nuclear ashes of partial O- and Si-burning. Kinematic evidence is consistent with ejection from a binary supernova progenitor; at least two stars have rest-frame velocities indicating they are unbound to the Galaxy. With masses and radii ranging between 0.20 and 0.28 M$$\odot$$ and between 0.16 and 0.60 R$$\odot$$, respectively, we speculate these inflated white dwarfs are the partly burnt remnants of either peculiar Type Iax or electron-capture supernovae. Adopting supernova rates from the literature, we estimate that ∼20 LP 40−365 stars brighter than 19 mag should be detectable within 2 kpc from the Sun at the end of the Gaia mission. We suggest that as they cool, these stars will evolve in their spectroscopic appearance, and eventually become peculiar O-rich white dwarfs. Finally, we stress that the discovery of new LP 40−365 stars will be useful to further constrain their evolution, supplying key boundary conditions to the modelling of explosion mechanisms, supernova rates, and nucleosynthetic yields of peculiar thermonuclear explosions.

Authors:

Raddi, R.  ^[1];

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Hollands, M. A. ^[2]; Koester, D. ^[3]; Hermes, J. J. ^[4]; Gänsicke, B. T. ^[2]; Heber, U. ^[1]; Shen, K. J. ^[5]; Townsley, D. M. ^[6]; Pala, A. F.  ^[7];

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Reding, J. S. ^[8]; Toloza, O. F. ^[2]; Pelisoli, I.  ^[9];

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Geier, S. ^[9]; Gentile Fusillo, N. P. ^[2]; Munari, U.  ^[10];

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Strader, J. ^[11]

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1. Dr. Remeis-Sternwarte, Friedrich Alexander Universität Erlangen-Nürnberg, Sternwartstr 7, D-96049 Bamberg, Germany
2. Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
3. Institut für Theoretische Physik und Astrophysik, Universität Kiel, D-24098 Kiel, Germany
4. Department of Astronomy, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA, Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255, USA
5. Department of Astronomy and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720, USA
6. Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35401, USA
7. Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK, European Southern Observatory, Karl-Schwarzschild-Str 2, D-85748 Garching, Germany
8. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255, USA
9. Institut fur Physik und Astronomie, Universität Potsdam, Haus 28, Karl-Liebknecht-Str 24/25, D-14476 Potsdam-Golm, Germany
10. INAF-Astronomical Observatory of Padova, I-36012 Asiago, Italy
11. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA

Publication Date:

2019-06-21

Sponsoring Org.:

USDOE

OSTI Identifier:

1560907

Resource Type:

Published Article

Journal Name:

Monthly Notices of the Royal Astronomical Society

Additional Journal Information:

Journal Name: Monthly Notices of the Royal Astronomical Society Journal Volume: 489 Journal Issue: 2; Journal ID: ISSN 0035-8711

Publisher:

Oxford University Press

Country of Publication:

United Kingdom

Language:

English