Optical/near-infrared observations of the black hole candidate XTE J1720-318: from high-soft to low-hard state

Abstract

Aims: 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. Methods: 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. Results: 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 8 magnitudes, XTE J1720-318 is likely to be an intermediate mass X-ray binary located at a distance between 3 and 10 kpc, 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.

arXiv commentAstronomy and Astrophysics (in press). 7 pages, 7 figures

References in corpus (9)

• The Properties of X-Ray and Optical Light Curves of X-Ray Novae
• Multiwavelength observations revealing the evolution of the outburst of the black hole XTE J1118+480
• Multiwavelength Observations of the Black Hole Candidate XTE J1550-564 during the 2000 Outburst
• The 2002 Outburst of the Black-Hole X-ray Binary 4U 1543-47: Optical and Infrared Light Curves
• The 2003 radio outburst of a new X-ray transient: XTE J1720-318
• High-energy observations of the state transition of the X-ray nova and black hole candidate XTE J1720-318
• Optical and near-infrared observations of the microquasar V4641 Sagittarii during the 1999 September outburst
• Near Infrared Observations of Galactic Black Hole Candidates
• The Infrared Counterpart of the X-Ray Nova XTE J1720-318

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