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XMM follow-up observations of two unidentified INTEGRAL sources

ATel #4250; M. Molina, R. Landi, L. Bassani (INAF/IASF Bologna), A. Bazzano, M. Fiocchi (INAF/IAPS Rome), A. J. Bird, S. P. Drave (University of Southampton)
on 11 Jul 2012; 12:22 UT
Credential Certification: Manuela Molina (molina@iasfbo.inaf.it)

Subjects: Radio, Infra-Red, X-ray, Gamma Ray, AGN, Blazar

We report the results of X-ray follow-up observations performed with XMM-Newton of two unidentified hard X-ray sources, AX J1753.5-2745 and IGR J17348-2045 listed in the INTEGRAL/IBIS 9-year Galactic Hard X-ray Survey (Krivonos et al. 2012, arXiv:1205.3941) and in 4th IBIS Survey Catalogue (Bird et al. 2010, ApJS, 186, 1) respectively. We assume a conservative XMM positional uncertainty of 5".

AX J1753.5-2745

No source was detected within the IBIS error circle in a previous Swift/XRT observation with an upper limit to any counterpart 0.3-10 keV flux of 2 x 10-13 erg cm-2 s-1 (Degenaar et al. 2012, A&A 540, 22). A source is instead detected serendipitously during a public XMM observation of a nearby region; we note however that the XMM field of view does not cover the entire IBIS error circle. This XMM source is located at R.A. (J2000) = 17h 53m 33.32s and Dec. (J2000) = -27d 46m 26.76s. It has a counterpart in a USNO-B1.0 object (USNO-B1.0 0622-0772087) with magnitudes R ~17-17.5, and B~19; two infrared counterparts are also found within the XMM positional uncertainty with J magnitude around 14.

The 2-10 keV flux is 0.66 x 10-13 erg cm-2 s-1 assuming a simple power law with Gamma = 1.8 and NH(Gal) = 0.98 x 1022 cm-2; this flux is compatible with the previous XRT upper limit. The source location low on the Galactic plane (l=1.894, b=-0.90) and the lack of a radio detection suggest that this may be a Galactic object.

IGR J17348-2045

Within the 90% IBIS error circle, XMM detects an object located at RA (J2000) = 17h 34m 58.89s and Dec. (J2000) = -20d 45m 31.0s. Within the XMM error circle, there is a USNO-B1.0 source, USNO-B1.0 0692-0466331, with magnitudes R~17 and B~19, also listed as a 2MASS object with J=10.5, H=9.4 and K=9. The source is also detected in radio (NVSS J173459-204533) with a 20 cm flux of 13.2 mJy and is listed in the WISE catalogue with the following magnitudes: W1=8.73, W2=8.75, W3=7.46, W4=4.85.

The 2-10 keV flux is 0.68 x 10-13 erg cm-2 s-1 adopting a power law with Gamma = 1.8 and NH(Gal) = 0.23 x 1022 cm-2. We further note that the source is listed as variable in the 4th IBIS Survey Catalogue.

The source location just above the Galactic plane (l=5.681, b= 6.37) and the radio detection suggest in this case that the source is an AGN. Furthermore, we suggest that IGR J17348-2045 is most likely a Blazar, since it is a radio loud object (Log R = Log(L5GHz/LB)= 2.1), is variable in X-rays and has infrared colours (W2-W3 = 1.30 and W1-W2 = -0.01) compatible with those of WISE blazars (Massaro et al. 2012, ApJ, 750, 13).