Detection of X-ray flaring activity from GX 339-4 using Swift

ATel #14351; Sabyasachi Pal (MCC/ICSP), Manoj Mandal (MCC), Mangal Hazra (MCC), Debasish Saha (MCC) and Arnab Ghanta (MCC)
on 26 Jan 2021; 17:53 UT
Credential Certification: Sabyasachi Pal (sabya.pal@gmail.com)

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The black hole binary system GX 339-4 went through frequent outbursts every 2-3 years (ATel #944, #2380, #6649, #12287, #12322). Recently MeerKAT radio observations revealed enhanced activity from the source in radio wavelengths (ATel #14336) and the flux density of the source started to increase from the first week of January. We report the detection of hard X-ray flaring activity from GX 339-4 using Swift/BAT (15-50 keV). The average X-ray flux from Swift/BAT reached 72±9 mCrab on MJD 59239 (25 January 2021).

We study the energy spectrum of GX 339-4 using the Swift/XRT on MJD 59239.218 (obs id -- 00032898250). From the preliminary analysis, the spectrum (0.6-10 keV) can be fitted using XSPEC with model phabs×(powerlaw+diskbb). The estimated photon index is ~1.63 and the X-ray flux is 9.5×10^-9 ergs/cm²/s in 1-10 keV.

MAXI/GSC (2-20 keV) also shows hints of enhanced X-ray activity. The flux has started to increase and reached a value of 33±14 mCrab (2-20 keV) on MJD 59240 (26th January 2021).

We encourage further multi-wavelength follow-up observations.

This research has made use of the MAXI data provided by RIKEN, JAXA, and the MAXI team.

Light Curve of GX339-4