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Recent optical burst of the symbiotic star CH Cygni

ATel #2394; A. Skopal, S. Shugarov, D. Chochol (AI SAS, Tatranska Lomnica)
on 21 Jan 2010; 14:39 UT
Credential Certification: Augustin Skopal (skopal@ta3.sk)

Subjects: Optical, X-ray, Cataclysmic Variable

Our recent UBVR photometric monitoring of the symbiotic star CH Cygni revealed a new, strong burst in its U light curve. From 2009 Sept. 25 to Oct. 21 the star brightened from U = 10.9 to U = 9.7, respectively. However, the slope of the brightening is unknown, because of a lack of the data. Then CH Cyg persisted at a bright stage at U ~ 9.6 to 2009 November 23, i.e. for 33 days. Following observations indicated a fading in the brightness to U ~ 11.1, as given by our last measurements on 2010 January 15th and 16th. These values are close to the level between the 2009 July flare (see ATel #2192) and this burst. This implies that the recent burst represents only a 1-2 months lasting activity superimposed on a gradual brightening, which started from 2008 October (U ~ 11.9), as can be seen at http://www.ta3.sk/~astrskop/symbphot/ch_cyg/chcyg_flare.png .

According to the X-ray monitoring of CH Cyg (see ATel #2046 and ATel #2245), the hard 2-10 keV emission correlates with that measured within the U passband (see the figure referred above). Therefore, further monitoring of CH Cyg at both the X-ray and the optical wavelengths is important to gain a better understanding of its active phases.