New X-ray observations of IQ Aurigae and alpha(2) Canum Venaticorum Probing the magnetically channeled wind shock model in A0p stars

Astronomy and Astrophysics (Impact Factor: 4.38). 05/2011; 531. DOI: 10.1051/0004-6361/201116843
Source: arXiv


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.

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    ABSTRACT: A type stars are expected to be X-ray dark, yet weak emission has been detected from several objects in this class. We present new Chandra/HRC-I observations of the A5 V star \beta{} Pictoris. It is clearly detected with a flux of 9+-2 10^{-4} counts/s. In comparison with previous data this constrains the emission mechanism and we find that the most likely explanation is an optically thin, collisionally dominated, thermal emission component with a temperature around 1.1 MK. We interpret this component as a very cool and dim corona, with \log L_X/L_{bol}=-8.2 (0.2-2.0 keV). Thus, it seems that \beta{} Pictoris shares more characteristics with cool stars than previously thought.
    The Astrophysical Journal 04/2012; 750(1):78. DOI:10.1088/0004-637X/750/1/78 · 5.99 Impact Factor

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