Follow-up observations of X-ray emitting hot subdwarf stars: the He-rich sdO BD +37° 1977
Journal
Date Issued
2015
Author(s)
Description
This work is based on observations obtained with XMM-Newton , an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. P.E. acknowledges a Fulbright Research Scholar grant administered by the US–Italy Fulbright Commission and is grateful to the Harvard–Smithsonian Center for Astrophysics for hosting him during his Fulbright exchange.
Abstract
We report on the results of the first XMM-Newton satellite observation of the luminous and helium-rich O-type subdwarf BD +37° 1977 carried out in April 2014. X-ray emission is detected with a flux of about 4 × 10-14 erg cm-2 s-1 (0.2-1.5 keV), corresponding to a fX/fbol ratio ~ 10-7; the source spectrum is very soft, and is well fit by the sum of two plasma components at different temperatures. Both characteristics are in agreement with what is observed in the main-sequence early-type stars, where the observed X-ray emission is due to turbulence and shocks in the stellar wind. A smaller but still significant stellar wind has also been observed in BD +37° 1977; therefore, we suggest that in this case the detected X-ray flux has the same origin.
Volume
580
Start page
A56
Issn Identifier
0004-6361
Ads BibCode
2015A&A...580A..56L
Rights
open.access
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