INTEGRAL hard X-ray detection of a new outburst from GX339-4

ATel #14354; V. Sguera (INAF-OAS Bologna, Italy), A. Bazzano, M. Fiocchi, L. Natalucci, P. Ubertini (INAF-IAPS Roma, Italy), A. J. Bird, V. Lepingwell (Univ. of Southampton, UK), A. Bodaghee (Georgia College & State University, USA), P. Charles (Univ. of Southampton), J. Chenevez (DTU Space, Denmark), E. Kuulkers (ESA/ESTEC, Noordwijk, The Netherlands), N. Masetti (INAF-OAS Bolonga, Italy)
on 27 Jan 2021; 09:32 UT
Credential Certification: Vito Sguera (sguera@iasfbo.inaf.it)

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Recent MeerKAT observations, from 4 January to 16 January, detected increased radio activity from the recurrent black hole X-ray transient GX339-4, suggesting that the source is likely entering into a new outburst phase (ATel #14336).

We report the INTEGRAL detection of increased hard X-ray activity from GX339-4 which confirms a new outburst. The source sky region has been covered during recent INTEGRAL Galactic plane observations carried out from 17 January 13:41 UTC to 18 January 16:46 UTC (revolution 2321) and from 21 January 18:32 UTC to 22 January 14:35 UTC (revolution 2323).

During revolution 2321, GX339-4 is detected at 6.2sigma level (22-60 keV) with a flux of 15.4+/-2.5 mCrab (1.6 x 10^-10 erg cm^-2 s^-1). No detection is achieved in the energy band 60-100 keV, the 2sigma upper limit is about 13 mCrab (6.5 x 10^-11 erg cm^-2 s^-1).

During revolution 2323 the source is detected with an increased hard X-ray flux in both energy bands 22-60 keV (51.5+/-4.3 mCrab or 5.5 x 10^-10 erg cm^-2 s^-1, 12 sigma) and 60-100 keV (74.6+/-11.7 mCrab, or 3.7 x 10^-10 erg cm^-2 s^-1, 6.4sigma).

The source was not in the JEM-X field of view during these revolutions.

The last outburst activity from GX339-4, as detected by INTEGRAL, dates back to January 2019 (ATel #12420). Further INTEGRAL Galactic plane observations in the direction of GX339-4 are planned for the next days. Results from the Galactic Plane Scanning are publicly available at: http://gps.iaps.inaf.it