Issue |
A&A
Volume 435, Number 1, May III 2005
|
|
---|---|---|
Page(s) | 9 - 16 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20042408 | |
Published online | 25 April 2005 |
Discovery of an X-ray binary in the outer SMC wing
Sternwarte, Universität Bonn Auf dem Hügel 71, 53121 Bonn, Germany e-mail: [pkahabka;mhilker]@astro.uni-bonn.de
Received:
22
November
2004
Accepted:
21
December
2004
The discovery of an X-ray binary RX J0209.6-7427 in the outer wing
of the SMC is reported from two archival ROSAT PSPC
observations. The data show variability in the X-ray light curve with
a timescale of ~40 days that probably is related to the binary
orbital period of the system. A mag star in the X-ray error
circle of the source is the likely optical counterpart. The optical
spectrum of the star shows
emission with an equivalent
width of
Å. The spectral type of the star is constrained
as B0-B1.5IV-Ve and consistent with that of a Be star. RX J0209.6-7427
is therefore a Be-type X-ray binary. The mean X-ray luminosity of the
source is derived to be ~
(for a distance of 60 kpc), which is comparable to luminosities derived for
Be-type X-ray binaries in the body of the SMC. This makes RX J0209.6-7427
the first candidate Be-type X-ray binary discovered in the outer SMC wing
that directly extends into the Magellanic Bridge. This finding is
consistent with the existence of a young (~10–30 Myr) stellar
population in the outer region of the SMC wing. Star formation due to an
encounter of the SMC with the LMC and the Magellanic system with the Galaxy
may explain this likely high-mass X-ray binary in an area
far from the main body of the SMC.
Key words: Magellanic Clouds / X-rays: binaries / binaries: general / stars: individual: RX J0209.6-7427 / stars: variables: general
© ESO, 2005
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