Precursors and outbursts of A 0535+26 in 2009-2011 observed by the MAXI/GSC and the Swift/BAT
Abstract
Over the three-year active period from 2008 September to 2011 November, the outburst behavior of the Be/X-ray binary A 0535+26 was continuously monitored with the MAXI/GSC and the Swift/BAT. The source exhibited nine outbursts, every binary revolution, of which two are categorized into the giant (type-II) outbursts. The recurrence period of these outbursts is found to be ∼ 115 d, significantly longer than the orbital period of 111.1 d. With the MAXI/GSC, a low-level active period, or a "precursor," was detected prior to at least four giant outbursts. The precursor recurrence period agrees with that of the giant outbursts. The period difference of the giant outbursts from the orbital period is possibly related to some structures in the circumstellar disc formed around the Be companion. Two scenarios, one based on a one-armed disc structure and the other a Be-disc precession, are discussed.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- February 2014
- DOI:
- 10.1093/pasj/pst002
- arXiv:
- arXiv:1308.5498
- Bibcode:
- 2014PASJ...66....9N
- Keywords:
-
- stars: individual (A 0535+26);
- stars: neutron;
- X-rays: binaries;
- X-rays: stars;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 15 pages, 7 figures, 1 table. Accepted for publication in PASJ