1–5 Jul 2019
Geological Museum
Europe/Copenhagen timezone

A white dwarf with an usual composition as a possible product of a binary merger

5 Jul 2019, 11:30
20m
Main Auditorium (Geological Museum)

Main Auditorium

Geological Museum

Øster Voldgade 5-7 DK-1350 Copenhagen
Talk Mergers

Speaker

Dr Mark Hollands (The University of Warwick)

Description

The merger of two white dwarfs with a combined mass below the Chandrasekhar-limit is expected to be non-explosive, resulting in a single massive white dwarf. However, because single star evolution can also produce massive white dwarfs, few known degenerate stars have categorically been confirmed as merger products.

We report the identification of a 1.15 $M_\odot$ white dwarf with a unique photospheric composition which is not explained through standard models of single star evolution. The stellar atmosphere is dominated by hydrogen, but with a C/H ratio of 0.15. The spectroscopic non-detection of helium and maximum convection zone mass of $M_\mathrm{cvz}/M_\mathrm{wd} = 10^{-10}$, imply an extremely small stellar envelope with a remarkably low helium fraction (considering the dredge up carbon from the interior). This new discovery potentially provides a new avenue to investigate a rare channel of binary-star evolution.

Primary author

Dr Mark Hollands (The University of Warwick)

Co-authors

Dr Pier-Emmanuel Tremblay (The University of Warwick) Prof. Boris Gaensicke (The University of Warwick) Prof. Detlev Koester (University of Kiel) Dr Nicola Gentile-Fusillo (The University of Warwick) Ms Paula Izquierdo (IAC) Mr Matthew Hoskin (The University of Warwick) Dr Paul Chote (The University of Warwick) Dr Danny Steeghs (The University of Warwick)

Presentation materials

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