INTEGRAL serendipitous observations of Swift J151857.0-572147 and detection at hard X-rays
ATel #16524; V. Sguera (INAF-OAS Bologna, Italy)
on 12 Mar 2024; 17:41 UT
Credential Certification: Lara Sidoli (sidoli@lambrate.inaf.it)
Subjects: X-ray, Transient
Swift J151857.0-572147 is a new X-ray transient discovered on 3 March 2024 (ATel #16500). Rapid follow-up observations at radio, optical, infrared and soft X-rays have been performed to determine its nature (ATels #16503, #16506, #16516, #16518, #16519).
We report on the INTEGRAL serendipitous hard X-ray detection of Swift J151857.0-572147 during public observations performed firstly from 8 March 2024 at 07:42 UTC to 9 March 2024 at 10:18 UTC and secondly from 10 March 2024 at 16:28 UTC to 11 March 2024 at 20:56 UTC.
From 8 to 9 March the source was serendipitously in the IBIS/ISGRI field of view for an
effective on-source exposure of 1 ks. It was detected at 38 sigma level and 10 sigma level in the energy bands 25-60 keV and 60-100 keV, respectively. The measured average fluxes are 232+/-6 mCrab (or 2.2 x 10
-9 erg cm
-2 s
-1) and 135+/-14 mCrab (or 7 x 10
-10 erg cm
-2 s
-1) in the energy bands 25-60 keV and 60-100 keV, respectively. No detection was obtained above 100 keV (100-150 keV) and the corresponding 3 sigma upper limit is 105 mCrab (or 4 x 10
-10 erg cm
-2 s
-1).
From 10 to 11 March the source was serendipitously in the IBIS/ISGRI field of view for an
effective on-source exposure of 2 ks. It was detected at 56 sigma level and 14 sigma level in the energy bands 25-60 keV and 60-100 keV, respectively. The measured average fluxes are 236+/-4.2 mCrab
and 131.2+/-9.4 mCrab in the energy bands 25-60 keV and 60-100 keV, respectively.
Such fluxes are compatible, within the uncertainties, with those measured a few days before.
No significant detection (i.e. above 5 sigma level) was obtained in the band 100-150 keV and the corresponding 3 sigma upper limit is 72 mCrab.
