Swift XRT/UVOT follow-up of blazar 4C+14.23 after a gamma-ray flare

ATel #2253; Y. T. Tanaka (ISAS/JAXA), D. Donato (NASA GSFC), S. Cutini (ASDC), D. Gasparrini (ASDC), C. C. Cheung (NRL/NRC), on behalf of the Fermi-LAT collaboration
on 22 Oct 2009; 20:28 UT
Credential Certification: Teddy Cheung (ccheung@milkyway.gsfc.nasa.gov)

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Following the Fermi-LAT detection of a GeV flare from the z=1.038 blazar 4C+14.23 on Oct 13th (ATEL #2243), two 4 ksec Swift observations were obtained -- on Oct 16th (XRT in WT mode) and 18th (XRT in PC mode). These observations confirm that the blazar has brightened in the X-ray and optical bands following the GeV flare.

The blazar is well detected in each XRT observation. Combining the 2 XRT exposures, the data are well fit by a power law with a photon index, Gamma=1.51 +/- 0.35 and an average 0.3-10 keV flux = 1.17 (+0.20/-0.24)e-12 erg/cm2/s (unabsorbed assuming Galactic NH = 7.6e20 cm-2). There is no significant X-ray variability detected between the 2 day span of the observations. This flux is ~5x larger than that observed in a previous shorter (0.94 ksec) Swift exposure obtained on Sep 1st (assuming the same photon index determined from the new Oct data).

The blazar is well detected with the UVOT at both epochs. On Oct 16th, the observed V- and W1-band magnitudes were 17.53 +/- 0.09 and 17.53 +/- 0.05, respectively (extinction corrections of A_V=0.29 and A_W1=0.87 are not applied). Relative to the Sep 1 observation, where only a W1-band image was obtained, the source has brightened (optical magnitude changed by -0.31 +/- 0.07 mag). This confirms the optical flaring detected by the KANATA telescope (ATEL #2246). From the Oct 18th observation, we find marginal evidence for fading between the two days in the V-band (delta_V = 0.23 +/- 0.13 mag), but no significant variability is observed in the W1-band (delta_W1 = 0.03 +/- 0.07).

In consideration of the recent activity of this source we encourage further multiwavelength observations. For this source the Fermi LAT contact persons are Yasuyuki T. Tanaka (tanaka@astro.isas.jaxa.jp), Hiromitsu Takahashi (hirotaka@hep01.hepl.hiroshima-u.ac.jp) and Stephen E. Healey (sehealey@stanford.edu).

We thank the Swift team for their rapid scheduling of these observations.