Swift follow-up of the flaring blazar PKS 0736+01

ATel #6742; F. D'Ammando (Univ. Bologna, INAF-IRA Bologna), M. Orienti (INAF-IRA Bologna) on behalf of the Fermi Large Area Telescope Collaboration
on 24 Nov 2014; 09:00 UT
Credential Certification: Filippo D'Ammando (filippo.dammando@fisica.unipg.it)

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Following the gamma-ray flare of the flat spectrum radio quasar PKS 0736+01 detected by Fermi LAT on 2014 November 20 (ATel #6731), a Swift target of opportunity observation was performed on November 21.

Swift/XRT data were taken in Photon Counting mode for a net exposure of about 4.4 ksec. The X-ray spectrum (0.3-10 keV) observed in 2014 November 21 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 = 7.8 x 10^20 cm^-2, Kalberla et al. 2005, A&A, 440, 775) and a photon index of 1.37+/-0.16. The corresponding observed 0.3-10 keV flux is (8.2+/-0.6) x10^-12 erg cm^-2 s^-1. This flux is about a factor of two higher than that observed by Swift/XRT on 2009 October 22, (4.2+/-0.4) x10^-12 erg cm^-2 s^-1, with a photon index of 1.66+/-0.15.

Simultaneous Swift/UVOT observations in 2014 November 21 found PKS 0736+01 about 1.3 mag brighter in V-band, 0.9 mag in U-band, and 0.5 mag in W2-band compared to the UVOT observations performed on 2009 October 22. The measured magnitudes are:

Band	2014-11-21	2009-10-22
V	15.29+/-0.06	16.56+/-0.09
B	15.86+/-0.06	17.01+/-0.07
U	15.18+/-0.06	16.09+/-0.07
W1	15.51+/-0.07	16.17+/-0.08
M2	15.76+/-0.06	16.37+/-0.08
W2	15.75+/-0.07	16.22+/-0.07

In consideration of the ongoing activity of this source, confirmed also by the Swift observations, we encourage further multiwavelength observations. For this source the Fermi LAT contact person is F. D'Ammando (dammando@ira.inaf.it).

We would like to thank the Swift Team for making these observations possible, in particular D. Malesani as the Swift Observatory Duty Scientist.