Updating the identification/classification of the INTEGRAL sources IGR J04288-67022 and Swift J0826.2-7033
ATel #10412; 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; 09:20 UT
Credential Certification: Angela Malizia (firstname.lastname@example.org)
Subjects: X-ray, Gamma Ray
We update the identification/classification of 2 unidentified soft gamma ray sources, namely IGR J04288-6702 and Swift J0826.2-7033,
listed in the latest INTEGRAL/IBIS deep extragalactic survey reported by Mereminskiy et al. (2016, MNRAS 459,140).
Swift-XRT pointings performed in the direction of this source indicate the presence of viable X-ray counterparts compatible with the
IBIS positional uncertainty. Although within the 90% IBIS error circle (4.2 arcmin) there is no X-ray detection, within the 99% one (5.94 arcmin) or at its border, there are 2 X-ray sources which are both visible also above 5 keV:
Source A is located at RA(J2000)= 04 27 49.15 and Dec (J2000)=-67 04 38.85 (3.99 arsec 90% error in position, 10 sigma detection
over 0.3-10 keV band, 6 sigma detection over 5-10 keV band).
Source B is located at RA(J2000)= 04 29 47.48 and Dec (J2000)=-67 03 18.87 (3.65 arsec 90% error in position, 20 sigma detection
over 0.3-10 keV band, 4.6 sigma detection over 5-10 keV band).
Both sources were discussed by Grebenev et al. (2013, MNRAS 428, 50) but disregarded as possible associations due to the fact that they are
outside the 90% IBIS positional uncertainty; however no other X ray sources are present in the XRT image.
Source A is a new gamma-ray loud, eclipsing low-mass X-ray binary seen by Fermi as 3FGL J0427.9-6704 (Strader et al. 2016, Ap.J 831, 89);
its XRT spectrum can be described by an absorbed power law
(photon index fixed at 1.7 and column density of 4.5 x 1022 at cm-2) with a 2-10 keV flux of
1.2 x 10-12 erg cm-2 s-1.
Source B is instead a new AGN at z=0.065 recently classified as a Seyfert 1.5 by Parisi et al. (2014, A&A 561, 67); its XRT spectrum is well fitted
by a simple power law with photon index 1.69 +/- 0.12, no intrinsic absorption and a 2-10 keV flux of 1.5 x 10-12 erg cm-2
Given their similar X-ray spectra, they can both contribute to the high energy emission although source A being closer to the IBIS
source location and also detected at GeV energies is probably a more likely association than source B.
We note that the X-ray counterpart of this source (1SXPS J082623.1-703143) is a non-magnetic CV at 90 pc distance (Parisi et al. 2013, A&A 545, A101)