info:eu-repo/semantics/article
Optical identification of IGR J18308-1232 as a cataclysmic variable
Autor
VAHRAM CHAVUSHYAN
Institución
Resumen
We report on a spectroscopic analysis of optical sources inside the error circle of the XMM-Newton slew source XMMLS1 J183049.6-123218 (see Ibarra et al., ATel #1527), associated with the unidentifiedINTEGRAL source IGR J18308-1232 (Bird et al. 2007, ApJS, 170, 175). The observations were performed on 2008 June 28, starting at 06:37 UT, with the Boller & Chivens spectrograph mounted on the 2.1m telescope of the Observatorio Astronomico Nacional (San Pedro Martir, Baja California, Mèxico), for a total exposure time of 7200 s. We found that the optical spectrum of source USNO-A2.0 0750-13371563 (with coordinates RA =18 30 49.88, DEC = -12 32 18.7 and magnitude R ~ 17.0) shows a red continuum, possibly absorbed by the Galactic dust along the line of sight; superimposed on this continuum several Balmer, HeI and HeII narrow emission lines at a redshift consistent with zero are apparent. The Halpha emission is detected with an EW ~ 22 Angstrom. This spectrum resembles that of a Cataclysmic Variable (similar to those reported in e.g. Masetti et al. 2006, A&A, 459, 21 and in Masetti et al. 2008, A&A, 482, 113), and the relative strength of the HeII 4686 Angstrom emission suggests the presence of a magnetic white dwarf in this system. Thus we identify the object USNO-A2.0 0750-13371563 as the optical counterpart of the hard X-ray source IGR J18308-1232, and as a new, possibly magnetic, Cataclysmic Variable.