VLBI observations of the shortest orbital period black hole binary, MAXI J1659−152

Z. Paragi; A. J. van der Horst; T. Belloni; J. C. A. Miller-Jones; J. Linford; G. Taylor; J. Yang; M. A. Garrett; J. Granot; C. Kouveliotou; E. Kuulkers; R. A. M. J. Wijers

doi:10.1093/mnras/stt545

VLBI observations of the shortest orbital period black hole binary, MAXI J1659−152

¹Joint Institute for VLBI in Europe, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands
²Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands
³INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate, Italy
⁴International Centre for Radio Astronomy Research – Curtin University, GPO Box U1987, Perth, WA 6845, Australia
⁵Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, NM 87131-0001, USA
⁶Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, NL-7990 AA Dwingeloo, the Netherlands
⁷Leiden Observatory, University of Leiden, PO Box 9513, NL-2300 RA Leiden, the Netherlands
⁸Departement of Natural Sciences, The Open University of Israel, PO Box 808, Ra’anana 43537, Israel
⁹Space Science Office, NASA/Marshall Space Flight Center, Huntsville, AL 38512, USA
¹⁰European Space Astronomy Centre (ESA/ESAC), Science Operations Department, E-28691 Villanueva de la Cañada, Madrid, Spain
¹¹Astronomical Institute, University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam, the Netherlands

↵★E-mail: zparagi{at}jive.nl

Accepted 2013 March 27.
Received 2013 March 27.
In original form 2012 September 4.
First published online April 28, 2013.

Abstract

The X-ray transient MAXI J1659−152 was discovered by Swift/Burst Alert Telescope and it was initially identified as a gamma-ray burst. Soon its Galactic origin and binary nature were established. There exists a wealth of multiwavelength monitoring data for this source, providing a great coverage of the full X-ray transition in this candidate black hole binary system. We obtained two epochs of European very long baseline interferometry (VLBI) Network (EVN) electronic-VLBI and four epochs of Very Long Baseline Array data of MAXI J1659−152 which show evidence for outflow in the early phases. The overall source properties (polarization, milliarcsecond-scale radio structure, flat radio spectrum) are described well with the presence of a compact jet in the system through the transition from the hard–intermediate to the soft X-ray spectral state. The apparent dependence of source size and the radio core position on the observed flux density (luminosity-dependent core shift) supports this interpretation as well. We see no evidence for major discrete ejecta during the outburst. For the source proper motion we derive 2σ upper limits of 115 μas d⁻¹ in right ascension, and 37 μas d⁻¹ in declination, over a time baseline of 12 d. These correspond to velocities of 1400 and 440 km s⁻¹, respectively, assuming a source distance of ∼7 kpc.