wift/XRT localization of the newly discovered transient IGR J17533-2928

ATel #14430; Sabyasachi Pal (MCC/ICSP), J. Chenevez (DTU/NSI, Denmark), Debasish Saha (MCC), Manoj Mandal (MCC)
on 2 Mar 2021; 19:11 UT
Credential Certification: Sabyasachi Pal (sabya.pal@gmail.com)

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A new weak X-ray transient IGR J17533-2928 was discovered between February 13-23, 2021 by the IBIS/ISGRI telescope (20-80 keV) on board INTEGRAL during the observation of Galactic centre region (ATEL #14425). The position of the transient measured by IBIS/ISGRI is R.A.=17h53m18s (268.323 deg); Dec.=-29d28'30" (-29.475 deg), equinox 2000.0, with uncertainty 2'.

We have analysed INTEGRAL/JEM-X data of IGR J17533-2928 and detected the source at 4 sigma (strongest pixel) for 47 ksec effective exposure in the combined JEMX-1+2 mosaic obtained between February 12 02:02 UTC and February 13 00:13 UTC (INTEGRAL revolution 2331). The source flux is measured at 3 +/-1 mCrab between 3-10 keV. The source position in JEM-X is RA=17h53m07s (268.28 deg); Dec=-29d27'36" (-29.46 deg) with an uncertainty radius of 1 arcmin (90% confidence).

Following the report of the discovery of the new transient, we requested a Target of Opportunity observation by Swift/XRT for better localization of the source. Swift/XRT observed the source on MJD 59272.96 (Obs Id-00014099001) with exposure of 1.9 ks. The preliminary analysis of Swift/XRT data reveals the location of the source at:

R.A.(J2000)=17h 53m 8.1s (268.2838 deg)

Dec.(J2000)=-29d 27m 36.4s (-29.4601 deg)

with a systematic error radius of 3.5 arc-seconds (90% confidence). This position is 222 arcmin from the above-mentioned position obtained by ISGRI. The average count rate in Swift/XRT (0.3-10 keV) is ~0.46 counts sec^-1.

We have analyzed the energy spectrum of the source and obtained a best fitted model with an absorbed powerlaw with Hydrogen column density (nH) 1.22±0.28 × 10²² cm^-2 and photon index 1.67±0.26 (reduced Chi-squared 0.382 for 941 degrees of freedom). The source flux in the energy range 0.8-10 keV is 0.31 photons (1.68 × 10^-9 ergs cm^-2 s^-1).