Bibcode
Zurita, C.; Kuulkers, E.; Bandyopadhyay, R. M.; Cackett, E. M.; Groot, P. J.; Orosz, J. A.; Torres, M. A. P.; Wijnands, R.
Bibliographical reference
Astronomy and Astrophysics, Volume 512, id.A26
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3
2010
Journal
Citations
6
Refereed citations
6
Description
Aims: We performed an optical/infrared study of the counterpart
of the low-mass X-ray binary KS 1731-260 to test its identification and
obtain information about the donor. Methods: Optical and infrared
images of the counterpart of KS 1731-260 were taken in two different
epochs (2001 and 2007) after the source returned to quiescence in
X-rays. We compared these observations with those obtained when KS
1731-260 was still active. Results: We confirm the identification
of KS 1731-260 with the previously proposed counterpart and improve its
position to α=17:34:13.46 and δ=-26:05:18.60. The H-band
magnitude of this candidate showed a decline of ~1.7 mag from outburst
to quiescence. In 2007 April we obtained R =22.8± 0.1 and I =
20.9 ± 0.1 for KS 1731-260. Similar optical brightness was
measured in June 2001 and July 2007. The intrinsic optical color R-I is
consistent with spectral types from F to G for the secondary although
there is a large excess over that from the secondary at the infrared
wavelengths. This may be due to emission from the cooler outer regions
of the accretion disk. We cannot rule out a brown dwarf as a donor star,
although it would require that the distance to the source is
significantly lower than the 7 kpc reported by Muno et al. (2000, ApJ,
542, 1016).
Chandra Fellow.
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