ASCA observations of γ2Velorum (WC8+O9I): the variable X-ray spectrum of colliding winds.

Details ASCA observations of γ2Velorum (WC8+O9I): the variable X-ray spectrum of colliding winds. ASCA observations of γ2Velorum (WC8+O9I): the variable X-ray spectrum of colliding winds.

Dec 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996mnras.283..589s&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Vol. Vol. 283, No. 2, p. 589 - 605

Astronomy and Astrophysics

Astronomy

67

Binaries: General -- Stars: Early-Type -- Stars: Individual: Γ2 Velorum -- Stars: Mass-Loss Stars: Wolf-Rayet -- X-Rays: Stars, Stellar Winds: Binaries, Stellar Winds: Wolf-Rayet Stars, Stellar Winds: X-Ray Variations, Stellar Winds: Collisions, Stellar Winds: Synthetic Spectra

Scientific paper

We present an analysis of two observations of the nearby Wolf-Rayet (WR)+O-star binary system γ2Velorum with the Advanced Satellite for Cosmology and Astrophysics (ASCA). These observations were taken at orbital phases φ=0.4 and 0.5, when the O star is close to being in front of the WR star. At phase φ=0.5, γ2Vel is approximately four times more luminous in X-rays than it is at φ=0.4. We fit the X-ray spectra using simple combinations of absorbed Raymond-Smith emission models. We find evidence of a cool (kT ˜0.3 keV) and a hot (kT ˜1.3 keV) component in each spectrum. The hotter component suffers from variable absorption which suggests that it originates in a localized region between the two stars. Between φ=0.4 and 0.5 the absorbing column for this hotter component drops by a factor of 3 which accounts for most of the corresponding increase in flux.
These observations are interpreted in terms of a colliding-wind model. The collision between the winds from the O star and the WR star generates a region of hot X-ray emitting gas. When the WR star is in front, the dense WR wind effectively absorbs all the X-ray flux from the wind collision. However, when the O star is in front the more diffuse wind of the O star allows substantially more flux from the wind collision to escape. Our ASCA data confirm the colliding-wind origin for the hard X-ray emission from y2 Vel, which we then fit to the ASCA spectra. This allows us to determine fundamental stellar wind parameters for both stellar components from the X-ray spectra. In particular, we determine a mass loss for the WC8 star of ˜3×10-5 Msun yr-1, a value 3 times lower than that determined by radio observations. The consequences of this are discussed.
We consider that we are definitely seeing colliding-wind emission and also show the great potential for X-ray spectroscopy in determining fundamental wind parameters of WR (and other hot luminous) stars.

Affiliated with

Also associated with

No associations

Rating

ASCA observations of γ2Velorum (WC8+O9I): the variable X-ray spectrum of colliding winds. does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with ASCA observations of γ2Velorum (WC8+O9I): the variable X-ray spectrum of colliding winds., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and ASCA observations of γ2Velorum (WC8+O9I): the variable X-ray spectrum of colliding winds. will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1506413