Issue |
A&A
Volume 440, Number 2, September III 2005
|
|
---|---|---|
Page(s) | 743 - 750 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20042617 | |
Published online | 01 September 2005 |
Multiwavelength studies of WR 21a and its surroundings
1
Instituto Argentino de Radioastronomía, C.C.5, (1894) Villa Elisa, Buenos Aires, Argentina e-mail: pbenaglia@fcaglp.unlp.edu.ar
2
Facultad de Cs. Astronómicas y Geofísicas, UNLP, Paseo del Bosque s/n, (1900) La Plata, Argentina
3
Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 1710, Australia
4
XMM-Newton Science Operations Centre, European Space Astronomy Centre, Apartado 50727, 28080 Madrid, Spain
Received:
27
December
2004
Accepted:
6
June
2005
We present results of high-resolution radio continuum
observations towards the binary star WR 21a (Wack 2134) obtained
with the Australia Telescope Compact Array (ATCA) at 4.8 and
8.64 GHz. We detected the system at 4.8 GHz (6 cm) with a flux
density of mJy and set an upper limit of 0.3 mJy at
8.64 GHz (3 cm). The derived spectral index of
(
) suggests the presence of
non-thermal emission, probably originating in a colliding-wind
region. A second, unrelated radio source was detected ~
north of WR 21a at (RA, Dec)
, with flux densities of 0.36
and 0.55 mJy at 4.8 and 8.64 GHz, respectively, resulting in
. H i observations in the area are dominated
by absorption against the prominent H ii region RCW 49.
Analysis of a complete set of archived X-ray observations of
WR 21a confirms its strong variability but throws into doubt
previous suggestions by Reig (1999) of a period of years for the
system. Finally, we comment on the association with the
nearby EGRET source 3EG J1027–5817.
Key words: stars: early-type / stars: individual: WR 21a / stars: winds, outflows / radio continuum: stars / ISM: bubbles / gamma-rays: observations
© ESO, 2005
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