Infrared counterparts of the two X-ray sources in the error circle of 2FGL J1551.9+0855

ATel #4555; F. Massaro (Stanford University), P. S. Cowperthwaite (University of Maryland), A. Paggi (SAO), R. D'Abrusco (SAO)
on 8 Nov 2012; 03:38 UT
Credential Certification: Francesco Massaro (francesco_mss@yahoo.it)

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Following the SWIFT detection of two X-ray sources located within the error circle of the Fermi/LAT source 2FGL J1551.9+0855 (ATEL #4551), we searched in the Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010 AJ, 140, 1868) catalog at the position of the Fermi source for a gamma-ray blazar candidate using the association method outlined in Massaro, F. et al. (2012 ApJ, 752, 61) and Massaro et al. (2012 ApJ, 750, 138). Our association procedure is based on infrared color analyses using WISE data.

Our search found a single source with IR colors typical of gamma-ray blazars within the Fermi positional uncertainty at 95% level of confidence. The source is WISE J155203.26+085047.4 and its coordinates are:
R.A.(J2000) = 15h52m03.26s
Dec. (J2000) = 08d50m47.5s.

According to the WISE All-sky catalog (available at http://wise2.ipac.caltech.edu/docs/release/allsky/ ), WISE J155203.26+085047.4 is detected in all four energy bands with the following magnitudes:
m(3.4 micron) = 12.270 +/- 0.024
m(4.6 micron) = 11.300 +/- 0.022
m(12 micron) = 8.597 +/- 0.023
m(22 micron) = 6.406 +/- 0.054

The WISE gamma-ray blazar candidate (WISE J155203.26+085047.4) is positionally consistent (0.17 arcsec offset) with the VLBA radio position of the BZBJ1552+0850 (R.A. (J2000): 15h52m03.2616s, Dec. (J2000): +08d50m47.335s, Kovalev Y.Y. et al. AJ, 133, 1236), as indicated in the Second Fermi LAT catalog (Nolan, P. L. 2012 ApJS, 199, 31). The IR position of WISE J155203.26+085047.4 is also consistent with the X-ray one (6.89 arcsec offset) reported in the ATEL #4551.

The second X-ray source described in (ATEL #4551): LSBC F727-V01 has also a counterpart in the WISE All-sky catalog: WISE J155140.54+085226.1 (R.A. (J2000): 15h 51m 40.55s, Dec. (J2000): 08d52m26.2s), consistent (0.44 arcsec offset) with the optical SDSS position (R.A. (J2000): 15h51m40.518s, Dec. (J2000): 08d52m26.15s). WISE J155140.54+085226.1 is detected in all four WISE bands with the following magnitudes:
m(3.4 micron) = 13.021 +/- 0.026
m(4.6 micron) = 12.757 +/- 0.029
m(12 micron) = 10.748 +/- 0.086
m(22 micron) = 8.723 +/- 0.371

However the IR colors of LSBC F727-V01 in the 3 dimensional parameter space are not consistent with those of the gamma-ray blazars (D'Abrusco, R. et al. 2012 ApJ, 748, 68), thus we conclude that 2FGL J1551.9+0855 is most probably associated to the blazar WISE J155203.26+085047.4 (alias BZBJ1552+0850) in agreement with the association reported in the Second Fermi LAT catalog (Nolan, P. L. 2012 ApJS, 199, 31).

This analysis makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration.

Additional details concerning the association procedure and the infrared colors of gamma-ray emitting blazars can be found also in Massaro, F. et al. (2011 ApJ, 740L, 48) and D'Abrusco, R. et al. (2012 ApJ, 748, 68)