Swift/BAT flux indicates Cyg X-3 enters a new gamma-ray active period
ATel #3439; W. Yu, Y. Xing (Shanghai Astronomical Observatory)
on 20 Jun 2011; 06:04 UT
Credential Certification: Wenfei Yu (wenfei@shao.ac.cn)
Subjects: Request for Observations, Binary
Gamma-ray flares (> 100 MeV) have been seen in Cyg X-3 whenever it transits to a low hard X-ray flux level (e.g., Tavani et al. 2009, Abdo et al. 2009). Our study of the correlated X-ray and gamma-ray activities with the RXTE/ASM, the Swift/BAT and the Fermi/LAT observations of Cyg X-3 yields an empirical relation between the BAT minimum flux reached and the peak flux of the gamma-ray flare, which suggests that Cyg X-3 should enter gamma-ray active periods whenever the 5-day averaged 15-50 keV flux goes below 0.12 crab (Yu & Xing, submitted to ApJ). In the past few days, the BAT daily averaged flux (15-50 keV) has been decreasing to a low level, reaching a 5-day averaged flux of 0.102+-0.002 crab (MJD 55727-55731), below the 0.12 crab threshold. This indicates that Cyg X-3 enters a new gamma-ray active period. Radio flares have been found associated with these gamma-ray flaring events. Multi-wavelength observations of Cyg X-3, especially radio observations with good coverage, are highly encouraged in order to determine the sequence of the occurrences of the radio and the gamma-ray flares.
