ASCA X - ray Spectroscopy of the Unusual B 0 V Star


We have obtained a high quality ASCA spectrum of the MK standard B0 V star Sco in order to test the standard wind-shock picture of OB star X-ray production. The uxes in three line complexes from ions indicative of hot plasma { Mg +10 , Si +12 , and S +14 { are measured, and we also present a global spectral t using a fairly standard multi-temperature, optically thin, collisional equilibrium model. We were able to achieve a statistically good t, but only by using the MeKaL plasma emission code (Mewe, Kaastra, & Liedahl 1995) and xing the elemental abundances at the photospheric values as determined by optical spectroscopy. The parameters of the The quantity of material with temperature in excess of 10 7 K on Sco is comparable to that with temperature in excess of 10 6 K on most other early B stars. The data cannot be explained by the standard line-force instability wind-shock mechanism. However more unusual shock mechanisms involving magnetically connned wind shocks or interactions between infalling matter and the ambient stellar wind cannot be ruled out. Alternately, a dynamo driven by diierential rotation could be powering coronal plasma. If magnetic elds are involved in any way then the star's extreme youth could play a role.

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@inproceedings{Cohen2007ASCAX, title={ASCA X - ray Spectroscopy of the Unusual B 0 V Star}, author={S . H . Cohen and Joseph P. Cassinelli and Wayne L. Waldron}, year={2007} }