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Swift-XRT follow-up of IGR J01157+6941 and IGR J21095+4322

ATel #10364; A. Malizia, R. Landi, L. Bassani, N. Masetti (IASF/INAF Bologna), A. Bazzano, M. Fiocchi, P. Ubertini (IAPS/INAF Rome), A. J. Bird (University of Southampton)
on 10 May 2017; 14:45 UT
Credential Certification: Angela Malizia (malizia@iasfbo.inaf.it)

Subjects: X-ray, Gamma Ray

Referred to by ATel #: 10447

In this telegram we report X-ray follow-up observations performed with Swift-XRT of 2 unidentified INTEGRAL sources, namely IGR J01157+6941 and IGR J21095+4322.
Both sources are reported as new persistent detections in the latest INTEGRAL/IBIS survey by Bird et al. (2016 ApJS, 223, 15).

IGR J01157+6941
XRT performed 4 pointings towards this source for a total exposure of 4862 sec. Within the 90% IBIS error circle there is no X-ray detection but within the 99% positional uncertainty XRT detects one X-ray source located at R.A.(J2000) = 01h 15m 48.79s and Dec.(J2000) = +69d 46m 00.8s (5.53 arcsec 90% positional uncertainty).
The XRT detection is around 4 sigma in the 0.3-10 keV band, with no counts above 3 keV. Inside the XRT error circle we only find the bright star TYC 4301-174-1 of spectral type K3V at a distance of 60 pc (Pickles et al 2010,PASP 122, 1437).
The XRT spectrum is broadly fitted with a power law absorbed by the Galactic column density of 3.3 x 1021 cm-2 and having a photon index fixed to 1.7 and a 2-10 keV flux of 2.7 x 10-13 erg cm-2 s-1. Given the lack of detection above 3 keV and the association to a star of spectral type unlike to emit at soft gamma-ray energies, we consider this association uncertain.

IGR J21095+4322
XRT performed 6 pointings towards this source for a total exposure of 5015 sec. Within the 90% IBIS error circle, XRT detects one X-ray source located at R.A.(J2000) = 21h 09m 24.21s and Dec.(J2000) = +43d 19m 35.73s (3.80 arcsec 90% positional uncertainty). The XRT detection is around 15.3 sigma in the 0.3-10 keV band and 9.6 sigma above 3 keV.
Within the XRT positional uncertainty we find two optical/IR objects (USNO-B1.0 1333-0426693/2MASS J21092411+4319319 and USNO B1.0 1333-0426688/2MASS J21092386+4319371) of which only the first is reported in the WISE catalogue (WISE J210924.07+431933.4) with colours (W1-W2=0.047, W2-W3=1.273) which are typical of stellar objects.
The XRT spectrum is well fitted with a power law absorbed by the Galactic column density of 9.5 x 1021 cm-2 and having a photon index of 1.56 [+0.26, -0.26] and a 2-10 keV flux of 3.34 x 10-12 erg cm-2 s-1. Optical spectroscopy of both objects located inside the XRT positional uncertainty is highly encouraged.