Partly burnt runaway stellar remnants from peculiar thermonuclear supernovae
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Published version
Date
2019-10-21
Authors
Raddi, R.
Hollands, M.A.
Koester, D.
Hermes, James J.
Gänsicke, B.T.
Heber, U.
Shen, K.J.
Townsley, D.M.
Pala, A.F.
Reding, J.S.
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Published version
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Citation
R. Raddi, M.A. Hollands, D. Koester, J.J. Hermes, B.T. Gänsicke, U. Heber, K.J. Shen, D.M. Townsley, A.F. Pala, J.S. Reding, O.F. Toloza, I. Pelisoli, S. Geier, N.P. Gentile Fusillo, U. Munari, J. Strader. 2019. "Partly burnt runaway stellar remnants from peculiar thermonuclear supernovae." Monthly Notices of the Royal Astronomical Society, Volume 489, Issue 2, pp. 1489 - 1508. https://doi.org/10.1093/mnras/stz1618
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⊙ and between 0.16 and 0.60 R⊙, 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.
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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 489, Issue 2, pp. 1489 - 1508. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.