| Issue |
A&A
Volume 545, September 2012
|
|
|---|---|---|
| Article Number | A123 | |
| Number of page(s) | 3 | |
| Section | Astrophysical processes | |
| DOI | https://doi.org/10.1051/0004-6361/201220228 | |
| Published online | 19 September 2012 | |
Oscillations of the Eddington capture sphere
1 Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warszawa, Poland
e-mail: wlodek@camk.edu.pl
2 Institute of Micromechanics and Photonics, ul. św A. Boboli 8, 02-525 Warszawa, Poland
e-mail: maciek.wielgus@gmail.com
3 Physics Department, Gothenburg University, 41296 Göteborg, Sweden
e-mail: gusstaad@student.gu.se; marek.abramowicz@physics.gu.se
4 Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo nám. 13, 74601 Opava, Czech Republic
Received: 14 August 2012
Accepted: 28 August 2012
We present a toy model of mildly super-Eddington, optically thin accretion onto a compact star in the Schwarzschild metric, which predicts periodic variations of luminosity when matter is supplied to the system at a constant accretion rate. These are related to the periodic appearance and disappearance of the Eddington capture sphere. In the model the frequency is found to vary inversely with the luminosity. If the input accretion rate varies (strictly) periodically, the luminosity variation is quasi-periodic, and the quality factor is inversely proportional to the relative amplitude of mass accretion fluctuations, with its largest value Q ≈ 1/(10 |δṀ/Ṁ|) attained in oscillations at about 1 to 2 kHz frequencies for a 2 M⊙ star.
Key words: accretion, accretion disks / gravitation / relativistic processes / stars: neutron / X-rays: binaries
© ESO, 2012
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