Centrum Astronomiczne im. M. Kopernika
Astronomy Division, Department of Physical Sciences, University Oulu
Astronomy Division, Department of Physical Sciences, University Oulu
Department of Physics, University of Durham
Max-Planck-Institut fur Gravitationsphysik, Albert-Einstein-Institut
出版者
宇宙航空研究開発機構
出版者（英）
Japan Aerospace Exploration Agency (JAXA)
雑誌名
宇宙航空研究開発機構特別資料
雑誌名(英)
JAXA Special Publication: Astrophysics with All-Sky X-Ray observations: 3rd International MAXI Workshop
巻
JAXA-SP-08-014E
ページ
70 - 75
発行年
2009-02-27
会議概要（会議名, 開催地, 会期, 主催者等）（英）
Astrophysics with All-Sky X-Ray observations: 3rd International MAXI Workshop (RIKEN, 10-12 June 2008)
抄録（英）
We review X-ray flux modulation from X-ray binaries on time scales corresponding to the orbital period and those at longer time scales (so called superorbital). Those modulations provide a powerful tool to constrain geometry of the accretion flow. The most common cause of the superorbital variability appears to be precession. We then discuss two specific examples of discoveries of a coupling between the two types of variability and their physical interpretation. One is Cyg X-1, a black-hole binary with a high-mass companion, in which case we find the presence of an accretion bulge formed by collision of the stellar wind with the outer edge of the precessing accretion disc. The other is 4U 1820-303, a neutron star accreting from a low-mass white dwarf, in which case we interpret the superorbital variability as accretion rate modulation induced by interactions in a triple stellar system. Then, the varying accretion rate leads to changes of the size of the accretion bulge in that system, obscuring the centrally-emitted X-rays.
Orbital and superorbital variability and their coupling in X-ray binaries
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