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Swift-XRT follow-up of IGR J04539+4502 and IGR J21171+3930

ATel #10468; A. Malizia, R. Landi, L. Bassani, V. Sguera (IASF/INAF Bologna), A. Bazzano, M. Fiocchi, P. Ubertini (IAPS/INAF Rome), A. J. Bird (University of Southampton)
on 6 Jun 2017; 13:47 UT
Credential Certification: Angela Malizia (malizia@iasfbo.inaf.it)

Subjects: X-ray, Gamma Ray, AGN

We report on X-ray follow-up observations performed with Swift-XRT of 2 unidentified INTEGRAL sources, namely IGR J04539+4502 and IGR J21171+3930.
Both sources are listed as new persistent detections in the latest INTEGRAL/IBIS survey by Bird et al. (2016 ApJS, 223, 15).

IGR J04539+4502
XRT performed 2 pointings towards this source for a total exposure of 4919 sec.
Within the 90% IBIS error circle, XRT detects one X-ray source located at R.A.(J2000) = 04h 54m 14.78s and Dec.(J2000) = +45d 03m 13.58s (6.12 arcsec 90% positional uncertainty). The XRT detection is around 4 sigma in the 0.3-10 keV band and 2.7 sigma above 3 keV. Inside the XRT error circle we only find the galaxy 2MASX J04541490+4503149 of unknown redshift also listed in the WISE catalogue as WISE J045414.88+450315.1 with infrared colours W1-W2=1.06 and W2-W3=3.81. The source is close (22 arcsec distance) to the radio emitting object 32P138 detected at 1420/408 MHz with a flux density of 16.4/33.8 mJy (Leahy and Roger 1996, A&A Suppl. 115,345).
Given the poor quality of the XRT spectrum, we estimated a 2-10 keV flux of 0.2 x 10-12 erg cm-2 s-1, by assuming a simple absorbed power law having photon index fixed to 1.7 and Galactic column density equal to 5.8 x 1021 cm-2.

IGR J21171+3930
XRT performed 7 pointings towards this source for a total exposure of 4255 sec.
Within the 90% IBIS error circle, XRT detects two X-ray sources only one of which remains visible above 3 keV. This source is located at R.A.(J2000) = 21h 17m 02.53s and Dec.(J2000) = +39d 27m 31.43s (4.45 arcsec 90% positional uncertainty). The XRT detection is around 7.5 sigma in the 0.3-10 keV band and 3.3 sigma above 3 keV.
Inside the XRT error circle we find an optical object USNO-B1.0 1294-0450859, also listed in the WISE catalogue as WISE J211702.38+392732.6 with infrared colours W1-W2=0.995 W2-W3=2.79. The XRT spectrum is well fitted with a power law absorbed by the Galactic column density of 2.76 x 1021 cm-2 and having a photon index of 2.3 +/- 0.5 and a 2-10 keV flux of 0.4 x 10-12 erg cm-2 s-1.
The Wise colours of both sources are typical of AGN (Secrest et al. 2015 ApJS, 221, 12), suggesting an extragalactic origin in each case.