Volume 552, April 2013
|Number of page(s)||20|
|Section||Stellar structure and evolution|
|Published online||19 March 2013|
MAXI J1659−152: the shortest orbital period black-hole transient in outburst⋆
European Space Astronomy Centre (ESA/ESAC), Science Operations
Department, 28691 Villanueva de la
2 Astrophysics Office, ZP12, NASA/Marshall Space Flight Center, Huntsville, AL 35812, USA
3 INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate ( LC), Italy
4 National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Kongens Lyngby, Denmark
5 ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
6 MIT Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139, USA
7 Department of Astronomy & Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA
8 School of Physics and Astronomy, University of Southampton, SO17 1BJ, UK
9 Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
10 Universities Space Research Association, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805, USA
Accepted: 21 December 2012
MAXI J1659−152 is a bright X-ray transient black-hole candidate binary system discovered in September 2010. We report here on MAXI, RXTE, Swift, and XMM-Newton observations during its 2010/2011 outburst. We find that during the first one and a half week of the outburst the X-ray light curves display drops in intensity at regular intervals, which we interpret as absorption dips. About three weeks into the outbursts, again drops in intensity are seen. These dips have, however, a spectral behaviour opposite to that of the absorption dips, and are related to fast spectral state changes (hence referred to as transition dips). The absorption dips recur with a period of 2.414 ± 0.005 h, which we interpret as the orbital period of the system. This implies that MAXI J1659−152 is the shortest period black-hole candidate binary known to date. The inclination of the accretion disk with respect to the line of sight is estimated to be 65–80°. We propose the companion to the black-hole candidate to be close to an M5 dwarf star, with a mass and radius of about 0.15–0.25 M⊙ and 0.2–0.25 R⊙, respectively. We derive that the companion had an initial mass of about 1.5 M⊙, which evolved to its current mass in about 5–6 billion years. The system is rather compact (orbital separation of ≳1.33 R⊙), and is located at a distance of 8.6 ± 3.7 kpc, with a height above the Galactic plane of 2.4 ± 1.0 kpc. The characteristics of short orbital period and high Galactic scale height are shared with two other transient black-hole candidate X-ray binaries, i.e., XTE J1118+480 and Swift J1735.5−0127. We suggest that all three are kicked out of the Galactic plane into the halo, rather than being formed in a globular cluster.
Key words: accretion, accretion disks / binaries: close / stars: individual: MAXI J1659-152 / X-rays: binaries
Table 1 is available in electronic form at http://www.aanda.org
© ESO, 2013
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