THE CELLULAR-AUTOMATON MODEL FOR THE VARIABILITY OF ACCRETION DISKS AROUND BLACK-HOLES - COMMENT

Citation
M. Abramowicz et G. Bao, THE CELLULAR-AUTOMATON MODEL FOR THE VARIABILITY OF ACCRETION DISKS AROUND BLACK-HOLES - COMMENT, Publications of the Astronomical Society of Japan, 46(5), 1994, pp. 523-525
Citations number
10
Categorie Soggetti
Astronomy & Astrophysics
ISSN journal
00046264
Volume
46
Issue
5
Year of publication
1994
Pages
523 - 525
Database
ISI
SICI code
0004-6264(1994)46:5<523:TCMFTV>2.0.ZU;2-4
Abstract
Stellar black-hole candidates and active galactic nuclei are believed to contain accretion disks around black holes. Their X-ray variability is characterized by power spectra with a power law dependence on the variability frequency. The power slope beta is in the range between 1 and 2 and its most typical value is around 1.5. Mineshige et al. (1994 , PASJ 46, 97) have recently simulated this type of accretion disk flu ctuations by a cellular automation ''ant-lion'' model and obtained bet a = 1.8. We point out that their model describes intrinsic fluctuation s of accretion disks and that the observed value beta = 1.8 is to be e xpected for disks oriented pole-on with respect to the detector. For d isks with a non-zero inclination, the observed power spectrum slope sh ould be flatter. We have calculated variability power spectra for accr etion disk fluctuations described by the Mineshige et al. model, and o btained beta = 1.7, 1.6, and 1.4 for disks with inclinations i = 20-de grees, 60-degrees, and 80-degrees respectively, in an excellent agreem ent with observations.