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ATEL # 2245; K. Mukai (NASA/GSFC/CRESST & UMBC), J.A. Kennea (PSU), G.J.M. Luna (CfA), J.L. Sokoloski (Columbia)
on 16 Oct 2009; 21:57 UT
Password Certification: Koji Mukai (firstname.lastname@example.org)
Subjects: X-ray, Request for Observations, Binaries
The latest observation in our continued RXTE monitoring of the symbiotic star, CH Cyg (ATel #2046), detects this object at a 2-10 keV flux of 6.7 x 10-11 ergs cm-2s-1. This is close to the highest X-ray flux levels ever measured for this object.
CH Cyg reached an even higher level in the RXTE observation on 2009 July 25, at 7.4 x 10-11 ergs cm-2s-1. However, this brightening was short-lived: in a Swift target-of-opportunity observation obtained on 2009 August 6, it was down to 1.64 x 10-11 ergs cm-2s-1 (2-10 keV). The July event can be characterized as a flare superimposed on a gradual brightening trend, as can be seen at the CH Cyg monitoring page. Unfortunately, neither the precise time of the onset or the total duration the flare is unknown, since the cadence of the X-ray observations is not high enough. Interestingly, an optical flare was detected, with a slight delay relative to the X-ray event (ATel #2192).
It is not clear if the October 16 measurement represents a similar flaring episode, or if it is the beginning of a stable high state. We encourage multi-wavelength observations of CH Cyg over the next days and weeks to determine which. If it is another flare, we have the opportunity to measure its duration at different wavelength ranges and therefore begin to understand its origin. If it is a stable high state, it will allow us to trigger a pre-approved TOO observation with Chandra HETG.
RXTE Monitoring of the Symbiotic Star, CH Cygni