Volume 644, December 2020
|Number of page(s)||9|
|Section||Letters to the Editor|
|Published online||14 December 2020|
Letter to the Editor
X-rays observations of a super-Chandrasekhar object reveal an ONe and a CO white dwarf merger product embedded in a putative SN Iax remnant⋆
Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
2 Department of Astronomy, Kazan Federal University, Kremlevskaya Str 18, Kazan, Russia
3 Sternberg Astronomical Institute, Lomonosov Moscow State University, Moscow 119234, Russia
4 Space Research Institute, Russian Academy of Sciences, Moscow 117997, Russia
5 Evgeni Kharadze Georgian National Astrophysical Observatory, Abastumani 0301, Georgia
6 Argelander-Institut für Astronomie, Universität Bonn, Bonn, Germany
7 Max-Planck-Institut für Radioastronomie, Bonn, Germany
Accepted: 25 November 2020
The merger of two white dwarfs (WDs) is a natural outcome of the evolution of many binary stars. Recently, a WD merger product, IRAS 00500+6713, was identified. IRAS 00500+6713 consists of a central star embedded in a circular nebula. The analysis of the optical spectrum of the central star revealed that it is hot, hydrogen, and helium free, and it drives an extremely fast wind with a record breaking speed. The nebula is visible in infrared and in the [O III] λ5007 Å line images. No nebula spectroscopy was obtained prior to our observations. Here we report the first deep X-ray imaging spectroscopic observations of IRAS 00500+6713. Both the central star and the nebula are detected in X-rays, heralding the WD merger products as a new distinct type of strong X-ray sources. Low-resolution X-ray spectra reveal large neon, magnesium, silicon, and sulfur enrichment of the central star and the nebula. We conclude that IRAS 00500+6713 resulted from a merger of an ONe and a CO WD, which supports earlier suggestion for a super-Chandrasekhar mass of this object. X-ray analysis indicates that the merger was associated with an episode of carbon burning and possibly accompanied by an SN Iax. In X-rays, we observe the point source associated with the merger product while the surrounding diffuse nebula is a supernova remnant. IRAS 00500+6713 will likely terminate its evolution with another peculiar Type I supernova, where the final core collapse to a neutron star might be induced by electron captures.
Key words: white dwarfs / stars: evolution / X-rays: stars / X-rays: individuals: IRAS 00500+6713
© ESO 2020
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