Optical Outburst of XTE J1118+480
ATel #386; U. Kiziloglu (METU), S. Balman (METU), A. Baykal (METU), E. Gogus (SU), A. Alpar (SU), C. Inam (Baskent)
on 13 Jan 2005; 17:34 UT
Credential Certification: Ersin Gogus (ersing@sabanciuniv.edu)
Subjects: Optical, Request for Observations, Binary, Black Hole, Transient
We report the monitoring of black hole X-ray transient XTE J1118+480(=KV UMa) during its new optical outburst and faint X-ray outburst. The data is obtained with the ROTSE IIId telescope (Robotic Optical Transient Search Experiment III) at TUG (Tubitak National Observatory) Antalya, Turkey (IAUC# 7418 , ATEL#64, #67, #383, #384, #385). The observations stared on UT 2004 Dec 12.9 and the source is still being monitored by our group. XTE J1118+480 was found in quiescence (using ROTSE calibrated [USNO A2.0] R magnitudes) on 2005 Jan 4.95 at a magnitude of R=17.7 . Following this date, on 2005 Jan 6.94 R=14.3, and on 2005 Jan 9.94 R=13.3. Our final observation on 2005 Jan 12.93 indicates R=12.93 for the source. The lightcurve is tending to a plateau (probable maximum). The rise in the light curve can not be fitted with a single power law or exponential function. We find that the rise can be modelled using a power law with an index of ~ 0.14
followed by an exponentail rise with a time constant of ~1.55 days. A light curve of the optical outburst of XTE J1118+480 can be found at the URL http://astroa.physics.metu.edu.tr/BHC along with images in quiesence and outburst.
