2013/06/28 by N. La Palombara, La Palombara, N., S. Mereghetti +9
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astronomy and Astrophysical Research #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Solar and Stellar Astrophysics (astro-ph.SR) #Stellar, planetary, and galactic studies #astro-ph.HE #astro-ph.SR
paper · pdf · doi:10.48550/arxiv.1306.6861
Comments 10 pages, 4 figures, 1 table. Proceedings of the XIth Hvar Astrophysical Colloquium "The Most Mysterious Binaries: Significance for Astrophysics", to be published in a special volume of the Central European Astrophysical Bulletin
arxiv created 2013/06/28 · openalex publication_date 2013/06/28 · arxiv updated 2013/07/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report on the results we obtained with XMM-Newton observations of HD49798 and BD+37 442, the only two sdO stars for which X-ray emission has been observed so far. HD is a single-lined spectroscopic binary with orbital period of 1.5 days. We could establish that its companion is a massive white dwarf with M = 1.28 Msun, which makes it a candidate type Ia supernova progenitor; we also detected a significant X-ray emission during the white-dwarf eclipse, which could be X-ray emission of the sdO star itself. In the case of BD+37 442, a luminous He-rich sdO that up to now was believed to be a single star, we discovered soft X-ray emission with a periodicity of 19.2 s. This indicates that also this hot subdwarf has a compact binary companion, either a white dwarf or a neutron star, most likely powered by accretion from the wind of the sdO star.