C.D.S. - SIMBAD4 rel 1.7 - 2021.04.15CEST06:41:23

2013A&A...553A..46M - Astronomy and Astrophysics, volume 553A, 46-46 (2013/5-1)

X-ray emission from the luminous O-type subdwarf HD 49798 and its compact companion.


Abstract (from CDS):

The X-ray source RXJ0648.0-4418 is the only confirmed binary system in which a compact object, most likely a massive white dwarf, accretes from a hot subdwarf companion, the bright sdO star HD49798. The X-ray emission from this system is characterized by two periodic modulations caused by an eclipse, at the orbital period of 1.55 d, and by the rotation of the compact object with a spin period of 13.2 s. In 2011 we obtained six short XMM-Newton observations centered at orbital phase 0.75, in order to study the system during the eclipse, and spaced at increasingly long time intervals in order to obtain an accurate measure of the spin-period evolution through phase-connected timing. The duration of the eclipse ingress and egress, ∼500 s, indicates the presence of an X-ray emitting region with dimensions of the order of a few 104 km, surrounding the pulsar and probably due to scattering in the companion's wind. We derived an upper limit on the spin-period derivative |{dot}(P)|<6x10–15 s/s, more than two orders of magnitude smaller than the previously available value. Significant X-ray emission is detected also during the 1.2 hours-long eclipse, with a luminosity of ∼3x1030 erg/s. The eclipse spectrum shows prominent emission lines of H- and He-like nitrogen, an overabundant element in HD49798. These findings support the suggestion that the X-ray emission observed during the eclipse originates in HD49798 and that the processes responsible for X-ray emission in the stellar winds of massive O stars are also at work in the much weaker winds of hot subdwarfs.

Abstract Copyright:

Journal keyword(s): subdwarfs - X-rays: binaries - stars: winds, outflows - stars: early-type - stars: individual: HD 49798

Simbad objects: 4

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Number of rows : 4

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 BD+37 442 HS* 01 58 33.4340086125 +38 34 23.846108332   9.69 9.92     sdOHe 61 0
2 HD 49798 HXB 06 48 04.7000758397 -44 18 58.432035331 6.758 8.017 8.287 8.391 8.543 sdO6 288 0
3 V* GP Vel HXB 09 02 06.8610736194 -40 33 16.896402010 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1388 0
4 V* V779 Cen HXB 11 21 15.0920367078 -60 37 25.627505233   14.4 12.27     O9III/Veq 1006 0

    Equat.    Gal    SGal    Ecl

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