2006A&A...455..639C -
Astronomy and Astrophysics, volume 455, 639-644 (2006/8-4)
Optical/near-infrared observations of the black hole candidate XTE J1720-318 : from high-soft to low-hard state.
CHATY S. and BESSOLAZ N.
Abstract (from CDS):
To gain a better understanding of high-energy Galactic sources, we observed the Galactic X-ray binary and black hole candidate XTE J1720-318 in the optical and near-infrared, just after the onset of its X-ray outburst in January, 2003. These observations were obtained with the ESO/NTT as the Target of Opportunity, in February and April 2003. We performed an accurate astrometry and analysed photometrical and spectroscopic observations. We then produced a colour-magnitude diagram, looked at the overall evolution of the multi-wavelength light curve, and analysed the spectral energy distribution. We discovered the optical counterpart in the R-band (R∼21.5) and confirmed the near-infrared counterpart. We show that, for an absorption between 6 and 8mag, XTE J1720-318 is likely to be an intermediate mass X-ray binary located at a distance between 3 and 10kpc, hosting a main sequence star of spectral type between late B and early G. Our second set of observations took place simultaneously with the third secondary outburst present in X-ray and near-infrared light curves. The evolution of its spectral energy distribution shows that XTE J1720-318 entered a transition from a high-soft to a low-hard state in-between the two observations.
Abstract Copyright:
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Journal keyword(s):
stars: binaries: close - stars: Hertzsprung-Russell (HR) and C-M diagrams - infrared: stars - X-rays: binaries - X-rays: individual: XTE J1720-318
Simbad objects:
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