Swift follow-up of the gamma-ray flaring blazar PKS 0402-362
ATel #3659; F. D'Ammando (INAF-IASF Palermo and CIFS), K. Sokolovsky (ASC Lebedev/SAI MSU) on behalf of the Fermi Large Area Telescope Collaboration and E. Hoversten (PSU)
on 24 Sep 2011; 17:21 UT
Credential Certification: Filippo D'Ammando (filippo.dammando@iasf-roma.inaf.it)
Subjects: Optical, X-ray, AGN, Blazar
Following the gamma-ray flare of the high redshift flat spectrum radio quasar PKS 0402-362 (also known as 1FGL J0403.9-3603, Abdo et al. 2010, ApJS, 188, 405; and 2FGL J0403.9-3604, Abdo et al. 2011, submitted to ApJS, arXiv:1108.1435; z = 1.417, Peterson et al. 1976, ApJ, 207, 5) detected by Fermi LAT on September 20-22, 2011 (ATel #3655), a Swift target of opportunity observation was performed on September 23.
Swift/XRT data were taken in Photon Counting mode for a total exposure of about 3.0 ksec. The X-ray spectrum (0.3-10 keV) can be fit by an absorbed power law model with a HI column density consistent with the Galactic value in the direction of the source (n_H = 6.03 x 10^19 cm^-2, Kalberla et al. 2005, A&A, 440, 775) and a photon index of 1.44+/-0.07. The corresponding observed 0.3-10 keV flux is (1.5+/-0.1) x10^-11 erg cm^-2 s^-1. This flux is a factor of five higher than that observed by Swift/XRT on 2008 January 1, (3.2+/-0.2 x10^-12 erg cm^-2 s^-1, with a photon index of 1.72+/-0.07), but a factor of 2 lower than that observed by Swift/XRT on 2010 February 5 (2.8+/-0.1 x10^-11 erg cm^-2 s^-1, with a photon index of 1.56+/-0.06), soon after the first gamma-ray flare detected by Fermi LAT (ATel #2413).
Swift/UVOT has detected the source at U = 16.51+/-0.07 on September 23, 2011. Previously, the source has been observed by Swift/UVOT in this band on January 1, 2008 at U = 16.75+/-0.06 and February 5, 2010 at U = 15.94+/-0.05, giving an indication of the fact that the ongoing flaring mechanism only marginally influences the optical band. Observations in B and V bands show similar behavior as in U band.
Further multiwavelength observations are encouraged. For this source the Fermi LAT contact person is J. Vandenbroucke (justinv@stanford.edu).
We would like to thank the Swift Team for making these observations possible.
