Recurrent outburst of X-ray Nova and black hole candidat KV UMa (XTE J1118+48) in January, 2005.

The observations of the Nova in the outburst were carried out in four nights on 2005 Jan 14-17 at 1-m Zeiss-1000 of the Special Astrophysical Observatory of the Russian Academy of Sciences with CCD EEV 42-40 in V band. The orbital elements were derived by R.Mark Wagner et al., ApJ V.556, 42, 2001. We improved the elements using SAO observations of this star in the quiet state. The ephemeris given for the exterior conjunction of the secondary star is the following: MinI =2451868.8101 +0.16993393*E. Figure 1 is a plot of V band photometry in the outburst, and Figure 2 is this one of Rc band for quiet state.

Figure 1. Outburst light curves. 2005 Jan 14 and 15 (top); 2005 Jan 16 (middle); 2005 Jan 17 (bottom).

Figure 2. Quiet state light curves. 2002 Jan 13 (red); 2003 Mar 30 and 31 (yellow); 2004 Mar 20 (blue).

Nova shows periodic variations with the amplitude of 0.02 mag, the maxima of the wave coincide with the phase of the exterior conjunction. This may be caused by the reflection effect on the surface of the secondary component, and/or by the eclipses of the hot crown of the BH by this star. In the quiet state, Nova has a double wave light curve for a period due to gravitational influence of BH. Our observations show the essential variations of the mean light level by about 0.2 mag.

Goranskij, V.P., Sternberg Astronomical Institute;
Barsukova, E.A. Special Astrophysical Observatory.

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