Simultaneous rapid hard X-ray and optical variability in AM Herculis: measurement of blob parameters
Open Access
- 1 September 1997
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 290 (1) , 145-159
- https://doi.org/10.1093/mnras/290.1.145
Abstract
We describe a study of the variability observed in the Ginga hard X-ray observation of AM Herculis. We find that the X-ray variability is best described by shot noise, with an exponential decay time-scale of 70 s. Interpreting the shots as due to inhomogeneous accretion, we derive a blob length-scale of ∼ 1010 cm at the white dwarf surface, a blob radius of 6 × 105−4 × 106 cm, and a mass of ∼ 1016 g. Simultaneous optical data show for the first time a correlation between the hard X-ray and optical red variability, which decreases towards bluer wavelengths. The observed correlations are explained as occurring from bremsstrahlung and cyclotron radiation from the main shock-heated accretion region near the white dwarf surface, with the degree of correlation decreasing towards bluer wavelengths due to the rapid decline of the cyclotron flux towards higher frequencies, and to the presence of Balmer continuum and line emission from the accretion stream in the blue bands.Keywords
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