AAS 200th meeting, Albuquerque, NM, June 2002
Session 74. Stellar Atmospheres and Circumstellar Material
Display, Thursday, June 6, 2002, 9:20am-4:00pm, SW Exhibit Hall

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[74.18] X-ray Emission from Bow Shocks around Clumps in Stellar Winds

N. Moeckel, J. Cho, J. P. Cassinelli (University of Wisconsin-Madison Astronomy Dept.)

Chandra Satellite observations have shown that for nearly all early-type stars the X-ray line profiles are nearly symmetric about rest line center. This is in contrast with profiles that are skewed toward the short wavelength side expected from standard shock models for X-ray emission in the stars. To test whether the profiles and the X-ray spectra can be better explained in terms of shocks around discrete clumps we have carried out a series of calculations of the structures and expected X-ray spectra of bow shocks around clumps in fast stellar winds. For the basic parameters we used the stagnating and infalling clump model of Howk et al. (2000) for the B0.5 V star tau Sco. The structure is calculated using the hydrodynamic model of Cho & Lazarian (2002) for shocks around an impenetrable sphere. The temperature and density distributions from these models are used to determine X-ray spectra around a clump with a given incident flow velocity and mass flux. We find that at velocities of around 1000 km/s the total flux per unit frontal area of a bow shock is comparable to that of a planar shock while the hard-to-total X-ray ratio is down by a factor of roughly 100. However, at velocities around 2250 km/s the total flux from clumps is lower by a factor of 30 while the hard-to-total ratio is now down by a factor of only 10.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.