Confirming the gamma-ray blazar nature of the low energy counterpart QSO PKS1725+123 of 2FGL J1727.9+1220 with WISE

ATel #4206; F. Massaro (Stanford University), A. Paggi (SAO), R. D'Abrusco (SAO)
on 24 Jun 2012; 03:28 UT
Credential Certification: Francesco Massaro (francesco_mss@yahoo.it)

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Following the near infrared NIR brightening of the QSO PKS1725+123 (=BZQJ1728+1215) (ATEL #4201), associated to the gamma-ray source 2FGL J1727.9+1220 in Nolan et al. (2012 ApJS, 199, 31), we searched in the Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010 AJ, 140, 1868) catalog at the VLBI position of the QSO PKS1725+123 (R.A.(J2000): 17h28m07.0512s, Dec.(J2000): +12d15m39.485s) reported in Beasley et al. (2002, ApJS, 141, 13).

We found a candidate infrared counterpart: WISE J172807.05+121539.6, with IR colors typical of gamma-ray blazars. Its coordinates are:
R.A.(J2000) = 17h28m07.05s (262.0293853 deg)
Dec. (J2000) = +12d15m39.65s (+12.2610152 deg).

As reported in the WISE All-sky catalog (available at http://wise2.ipac.caltech.edu/docs/release/allsky/ ), WISE J160437.36+571436.6 is detected in all four energy bands with the following magnitudes:
m(3.4 micron) = 13.665 +/- 0.026
m(4.6 micron) = 12.499 +/- 0.025
m(12 micron) = 9.493 +/- 0.035
m(22 micron) = 6.963 +/- 0.076

The WISE gamma-ray blazar candidate (WISE J172807.05+121539.6) is positionally consistent (0.167 arcsec offset) with the VLBI position reported in Beasley et al. (2002, ApJS, 141, 13).

Then, we searched in the WISE all-sky catalog at the position of the Fermi source 2FGL J1727.9+1220 (R.A.(J2000): 261.982 deg, Dec.(J2000): +12.346238) with a searching radius of 0.144 deg (corresponding to the 95% level of confidence), for a gamma-ray blazar candidate. We used the association procedure outlined in Massaro, F. et al. (2011 ApJ, 740L, 48) and in Massaro, F. et al. (2012 ApJ, 752, 61), based on infrared color analyses using WISE data. We found that according to our method WISE J172807.05+121539.6 is the unique gamma-ray blazar candidate within the searching region out of 964 IR sources present therein. Our association is in agreement with the PKS1725+123 (=BZQJ1728+1215) association reported in Nolan et al. (2012 ApJS, 199, 31) and in Ackermann et al. (2011 ApJ, 743, 171).

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 can be found in D'Abrusco, R. et al. 2012 ApJ, 748, 68; Massaro, F. et al. 2012 ApJ, 750, 138; Massaro, F., et al. 2012 ApJ, 750L, 35.