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Swift/BAT detects of a new X-ray outburst of GX 339-4

ATel #6649; Zhen Yan, Wenda Zhang, Hui Zhang, Holger Stiele and Wenfei Yu (Shanghai Astronomical Observatory)
on 31 Oct 2014; 10:31 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Wenfei Yu (wenfei@shao.ac.cn)

Subjects: X-ray, Request for Observations, Binary, Black Hole, Transient

Referred to by ATel #: 7009, 7201, 7434, 7649, 10797

The Swift/BAT hard X-ray monitoring has shown that the X-ray intensity of GX 339-4 in the 15-50 keV band has gradually increased in the last few days, which indicates a start of a new X-ray outburst of the black hole transient after the source has remained quiescent for a year or so. The source intensities on MJD 56959 (2014-10-29) and MJD 56960 were about 0.0095+-0.0019 and 0.0128+-0.0014 counts/cm^2/s, respectively. We found the average intensity of GX 339-4 in the X-ray band is about 0.0022+-0.0052 counts/cm^2/s during the entire period of the Swift/BAT coverage when the source intensity was lower than 0.023 counts/cm^2/s (~ 0.1 crab). Each of this flux values measured on these two days is actually larger than the average intensity by more than 1 sigma and a trend of increase in the hard X-ray intensity is seen. Multi-wavelength observations are highly encouraged.