IGR J17503-2636: a new X-ray transient discovered by INTEGRAL and confirmed by Swift

ATel #11952; J. Chenevez, G. Jaisawal (DTU Space, Denmark), E. Kuulkers (ESA/ESTEC, The Netherlands), C. Sanchez-Fernandez (ESA/ESAC, Spain), A. Bazzano (INAF/IAPS, Italy), A. Paizis (INAF/IASF-Mi, Italy), A. Bodaghee (GCSU, USA), S. Brandt, N. Lund (DTU Space, Denmark), E. Bozzo, C. Ferrigno (ISDC, Switzerland), on behalf of a larger collaboration
on 14 Aug 2018; 19:39 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Jerome CHENEVEZ (jerome@space.dtu.dk)

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The X-ray monitor JEM-X on-board the INTEGRAL satellite has discovered a new X-ray transient source during the recent Galactic Bulge observation performed on August 11^th (revolution 1986) from UTC 07:44 to 12:30 (ATel #438, Kuulkers et al. 2007, A&A 466, 595, see also: http://integral.esac.esa.int/BULGE).

The source is detected at 7 σ for an effective exposure time of 17.9 ks on the combined JEM-X mosaics from which we obtain the following fluxes:
12 ±2 mCrab (≈2.0×10^-10 erg/cm²/s) between 3-10 keV,
17 ±3 mCrab (≈1.9×10^-10 erg/cm²/s) between 10-25 keV.
JEM-X sees the source at the following position:
RA = 267.58°, Dec = -26.61° with an uncertainty of 1.5 arcmin
leading to the new source name: IGR J17503-2636.

The source is not detected by IBIS/ISGRI above 20 keV, and we estimate a 3-σ upper limit about 10 mCrab (20-40 keV).

Thanks to a 1-ks exposure with Swift/XRT in PC mode between August 13^th 19:41-20:13 (UTC) we can refine the source position at:
RA = 267.57527° = 17h 50m 18.06s
Dec = -26.60458° = -26d 36m 16.5s.
The error radius is 2.2 arcsec (90% confidence) obtained with the enhanced method using Swift/UVOT provided by the on-line Swift/XRT data product tool (Evans et al. 2009, MNRAS 397, 1177).

The Swift/XRT 0.3-10 keV count rate was increasing between the two snapshots from 0.3 to 0.5 c/s. The average spectrum is highly absorbed with a derived absorption column between (6.2-13.7)×10²² cm^-2 (for a galactic column density of 1.3×10²² cm^-2 in that direction). The observed 0.3-10 keV flux is estimated between (2.0-8.3)×10^-11 erg/cm²/s.

The next INTEGRAL observations of the Galactic Bulge region are currently scheduled on August 17^th and will continue at a rough cadence of one-two observations per week until October 20^th. Multi-wavelength follow-up observations are encouraged to unveil the nature of IGR J17503-2636.
We thank the Swift Team for scheduling the ToO observation with short notice.