Simultaneous rapid hard X-ray and optical variability in AMHerculis: measurement of blob parameters
Abstract
We describe a study of the variability observed in the Ginga hard X-ray observation of AMHerculis. We find that the X-ray variability is best described by shot noise, with an exponential decay time-scale of 70s. Interpreting the shots as due to inhomogeneous accretion, we derive a blob length-scale of ~10^10 cm at the white dwarf surface, a blob radius of 6x10^5-4x10^6 cm, and a mass of ~10^16g. 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 1997
- DOI:
- 10.1093/mnras/290.1.145
- Bibcode:
- 1997MNRAS.290..145B
- Keywords:
-
- ACCRETION;
- ACCRETION DISCS;
- BINARIES: CLOSE;
- STARS: INDIVIDUAL: AM HER;
- NOVAE;
- CATACLYSMIC VARIABLES;
- X-RAYS: STARS