INTEGRAL detection of 2S 1553-542

The transient source 2S 1553−542 is an accreting X-ray pulsar with a Be optical companion discovered by the SAS-3 observatory in 1975 (Apparao et al., 1978, Nature, 271, 225). Increased activity from the source was detected in 2007 by Swift/BAT and Swift/XRT instruments (ATel #1345, #1371) and one year later by RXTE/PCA (ATel #1373).

Activity from this source was also recently reported by Fermi/GBM and Swift/MAXI (ATel #14301 and #14308) During a recent INTEGRAL public observation of the Galactic Plane (revolution 2321), performed between 2021-01-17 13:41:03 and 2021-01-18 16:58:14 UTC, activity from this transient was detected.

The 22-60 keV IBIS/ISGRI flux corresponds to 26.1 ± 2.2 mCrab (2.8 ± 0.2 x 10-10 erg cm-2 s-1) with an effective exposure time of 16 ks. 2S 1553-542 was within the JEM-X field of view at 71 sigmas in the combined JEM-X1 and JEM-X2 mosaic for a total effective exposure of 40.8 ks on the source. The measured fluxes are 57 ± 1 mCrab (8.6 ± 0.1 x 10-10 erg cm-2 s-1) and 58 ± 4 mCrab (6.1 ± 0.4 x 10-10 erg cm-2 s-1) in the energy bands 3-10 and 10-25 keV, respectively.

All the data have been analysed using the Offline Scientific Analysis software version 11.0 (OSA11). Results from the Galactic Plane Scanning are publicly available at: http://gps.iaps.inaf.it