Updating the X-ray association of the INTEGRAL sources IGR J05104-6910 and IGR J12412+3007

ATel #10411; A. Malizia, L. Bassani, V. Sguera ( IASF/INAF Bologna), A. Bazzano, M. T. Fiocchi, P. Ubertini (IAPS/INAF Rome), A. J. Bird (University of Southampton)
on 22 May 2017; 09:17 UT
Credential Certification: Angela Malizia (malizia@iasfbo.inaf.it)

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We update the identification/classification of 2 unidentified soft gamma ray sources, namely IGR J05104-6910 and IGR J12412+3007 using Swift XRT images covering the IBIS positional uncertainty of 4.20 (90%) or 5.94 (99%) arcmin. Both sources are listed in the latest INTEGRAL/IBIS deep extragalactic survey reported by Mereminskiy et al. (2016, MNRAS 459, 140).

IGR J05104-6910
In this case we analysed a long exposure of 9000 sec made in January 2008 in the direction of the source.
There is only one X-ray source inside the 90% IBIS error circle (RA(J2000)= 05 10 39.91, Dec (J2000)= -69 07 05.48, 4.09 arcsec 90% error in position); however this source is very weak in X-rays (1.7 x 10^-14 erg cm^-2 sec^-1, 0.3-10 keV band) and too soft to be a likely counterpart to the INTEGRAL object.
Four other X-ray sources are present within the 99% positional uncertainty, but all of them are also too weak and soft in X-rays to be the correct association. We note however, that a bright source detected at 20 sigma c.l. over the 0.3-10 keV band and also seen above 5 keV (5.8 sigma c.l.) is present outside the 99% IBIS positional uncertainty (at 6.9 arcmin distance). The source coordinates are RA(J2000)= 05 09 15.58 and Dec (J2000)= -69 08 04.18 (3.65 arcsec 90% error in position) and its flux is 8.5 x 10^-13 erg cm^-2 s^-1 in the 0.3-10 keV band. This source, discussed also by Grebenev et al. (2013, MNRAS 428, 50), was rejected as a likely association because not detected at high energies. Within the XRT error circle we find the IR source 2MASS J05091554-6908057. There are indications that the object may be variable in optical (Zebrun et al. 2001 A&A 51, 317) as well as in X-rays (see in 3XMM-DR6 ); furthermore it is classified as a a young stellar object candidate in Simbad.

IGR J12412+3007
Four SWIFT/XRT pointings performed in December 2014 (total exposure 2470 sec) in the direction of the source found two X-ray sources, one (source A) within the 99% INTEGRAL error circle and one(source B) just outside it (6.5 arcmin distance). The source positions are:
Source A at RA(J2000)= 12 40 52.60, Dec (J2000)=+30 04 28.3 (6.1 arsec 90% error in position, 3 sigma detection over 0.3-10 keV band),
Source B at RA(J2000)= 12 40 57.84, Dec (J2000)=+30 13 13.0 (5.6 arsec 90% error in position, 4 sigma detection over 0.3-10 keV band). None of these two sources is visible above 3 keV but this maybe due to the short XRT exposure.
The 2-10 keV flux is 1.8 x 10^-13 erg cm^-2 s^-1 and 2.3 x 10^-13 erg cm^-2 s^-1 for source A and B respectively, assuming a simple power law with index fixed to 1.7 and only Galactic absorption.
We note that both sources are listed in the catalogue of candidate quasars by Brescia et al. (2015, MNRAS 450, 3893) as well as in the AllWISE catalogue with colours ( W1-W2=0.72 and W2-W3> 2.92 for source A and W1-W2=0.89, W2-W3=1.64 for source B) that are typical of AGN (Mateos et al.2012, MNRAS 426, 3271) suggesting an extragalactic nature for both objects.