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MAXI J1659-152: the shortest period black-hole binary?

ATEL # 2912; E. Kuulkers, A. Ibarra, A. Pollock , A. Parmar (ESA/ESAC, Spain), J. Chenevez (DTU Space, Denmark), C. Kouveliotou (NASA/MSFC), A.J. van der Horst (NASA/MSFC/ORAU), Z. Paragi (JIVE), J. Granot (Univ. Hertfordshire), G.B. Taylor (Univ. New Mexico), on behalf of a larger collaboration
on 7 Oct 2010; 21:07 UT
Password Certification: Erik Kuulkers (

Subjects: X-ray, Binaries, Black Holes, Transients, Variables
Referred to by ATEL #: 2926, 2999

Observations of MAXI J1659-152 (Negoro et al. 2010, ATel #2873; Mangano et al. 2010, GCN #11296) with XMM-Newton on 27 and 28 September (Kuulkers et al. 2010, ATel #2887) clearly reveal variations in the light-curve similar to that reported from Swift/XRT observations (Kennea et al. 2010, ATel #2877). The dipping episodes as seen in the preliminary released data from the XMM/EPIC-pn (0.15-15 keV) and XMM/RGS (0.32 keV) instruments recur approximately every 2.4-2.5 hours, and show irregular structure which lasts between about 5 and 40 min. Our simultaneous INTEGRAL/JEM-X (3-35 keV) observations (Kuulkers et al. 2010, ATel #2888) confirm this dipping activity.

By analogy with other low-mass X-ray binaries, we interpret these structures as X-ray dips (rather than eclipses) occurring every orbital period. Occasionally, intermittent, shallower, dips are also seen. If the compact object is indeed a black hole (Kalamkar et al. 2010, ATel #2881), the 2.4-2.5 hour period is to our knowledge the shortest among the currently known (candidate) black-hole binaries. We encourage multi-wavelength follow-up observations to investigate further the nature of this source.

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