New X-ray observations of IQ Aurigae and alpha2 Canum Venaticorum - Probing the magnetically channelled wind shock model in A0p stars

Abstract

We present new X-ray observations of the A0p stars alpha^2 CVn (log Lx < 26.0 erg/s) and IQ Aur (log Lx = 29.6 erg/s) and find that their X-ray luminosities differ by at least three orders of magnitude. IQ Aur possesses a strong cool plasma component with X-ray emitting regions located well above the stellar surface, but also significant amounts of hot plasma. Further, a large X-ray flare is detected from IQ Aur, implying the presence of magnetic reconnection. Our comparison study of similar stars indicates that the occurrence of X-ray emission generated by magnetically channelled wind shocks (MCWS) strongly depends on stellar properties. X-ray emission is preferably generated by more luminous and massive objects such as IQ Aur. The MCWS scenario can consistently describe the X-ray emission of these A0p stars, assuming that the very strong magnetic confinement of the stellar wind has led to the build up of a rigidly rotating disk around the star, where magnetic reconnection and centrifugal breakout events occur.

11 pages, 10 figures, accepted by A&A

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• Outstanding X-ray emission from the stellar radio pulsar CU Virginis
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• Mass loss and magnetospheres of massive stars
• Superfast Line Profile Variations in the Spectra of OBA Stars III: A0 Star ${\alpha }^2$CVn, New Results
• A Deep Chandra Observation of the Giant HII Region N11 I. X-ray Sources in the Field
• Coronal and chromospheric emission in A-type stars