IGR J16194–2810: a new symbiotic X-ray binary*
INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy e-mail: firstname.lastname@example.org
2 School of Physics & Astronomy, University of Southampton, Southampton, Hampshire, SO17 1BJ, UK
3 ASI Science Data Center, via Galileo Galilei, 00044 Frascati, Italy
4 South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
5 Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USA
6 INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Roma, Via Fosso del Cavaliere 100, 00133 Roma, Italy
Accepted: 24 April 2007
We here report on the multiwavelength study which led us to the identification of X-ray source IGR J16194-2810 as a new Symbiotic X-ray Binary (SyXB), that is, a rare type of Low Mass X-ray Binary (LMXB) composed of a M-type giant and a compact object. Using the accurate X-ray position allowed by Swift/XRT data, we pinpointed the optical counterpart, a M2 III star. Besides, the combined use of the spectral information afforded by XRT and INTEGRAL/IBIS shows that the 0.5-200 keV spectrum of this source can be described with an absorbed Comptonization model, usually found in LMXBs and, in particular, in SyXBs. No long-term (days to months) periodicities are detected in the IBIS data. The time coverage afforded by XRT reveals shot-noise variability typical of accreting Galactic X-ray sources, but is not good enough to explore the presence of X-ray short-term (seconds to hours) oscillations in detail. By using the above information, we infer important parameters for this source such as its distance (~3.7 kpc) and X-ray luminosity (~ erg s-1 in the 0.5-200 keV band), and we give a description for this system (typical of SyXBs) in which a compact object (possibly a neutron star) accretes from the wind of its M-type giant companion. We also draw some comparisons between IGR J16194-2810 and other sources belonging to this subclass, finding that this object resembles SyXBs 4U 1700+24 and 4U 1954+31.
Key words: astrometry / stars: binaries: general / X-rays: binaries / stars: neutron / stars: individual: IGR J16194-2810
Partly based on X-ray observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA, and on optical observations collected at SAAO, South Africa.
© ESO, 2007