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On the optical activity of GRO J2058+42 (CXOU J205847.5+414637) prior X-ray to outburst.

ATel #1517; U., Kiziloglu; N., Kiziloglu; A. Baykal; S. K. Yerli; M. Ozbey (METU)
on 11 May 2008; 14:14 UT
Credential Certification: Umit Kiziloglu (umk@astroa.physics.metu.edu.tr)

Subjects: Optical, Binary, Star, Transient, Variables, Pulsar

Recent Swift/BAT observations (ATel #1516) report the onset of a new X-ray outburst of the X-ray binary and pulsar GRO J2058+42. Our optical monitoring of CXOU J205847.5+414637, which is identified as the optical counterpart (Reig et al., ATel #308(2004), Wilson et al., ApJ, 622, 1024 (2005)), with ROTSEIIId telescope (Akerlof et al., PASP, 115, 132 (2003) on Bakirlitepe, TUBITAK National Observatory, Turkey, continues starting from MJD 53500. The X-ray outburst seems to be a result of a long optical activity (beginning around MJD 54100) (Kiziloglu et al., IBVS, no:5821 (2008)) after a period of optical quiescence (Kiziloglu et al., AA, 470,1023 (2007)). We detected at least one non-radial pulsation frequency for this system prior to increase in optical light curve. The X-ray outburst occurs during the decrease of optical light from its maximum value (R-band ~14.15), as seen in the weekly averaged ROTSEIIId light curve. The increase from the optical quiescence is about 0.3 mag. The weekly averaged ROTSE R-band light curve can be seen at: http://astroa.physics.metu.edu.tr/~umk/2058.ps