Swift follow-up confirms the high flaring state of the blazar PMN J2345-1555

ATel #2986; S. Kaufmann (LSW Heidelberg) on behalf of the ATOM Team, F. D'Ammando (INAF-IASF Palermo) on behalf of the Fermi LAT Collaboration, and J. Gelbord (PSU)
on 30 Oct 2010; 18:49 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Stefan J. Wagner (swagner@lsw.uni-heidelberg.de)

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Following the detection on 24 October 2010 of simultaneous optical and gamma-ray flares from the intermediate redshift (z=0.621) flat spectrum radio quasar PMN J2345-1555 by ATOM and Fermi LAT (ATel #2972), Swift target of opportunity observations have been performed on 27/28 October. Swift/XRT data were taken in Photon Counting mode for a total exposure of 9.7 ks. 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 = 1.74 x10^20 cm^-2, Kalberla et al. 2005) and a photon index of 1.8+/-0.2, indicating that the X-ray emission is dominated by the inverse Compton emission. The corresponding unabsorbed 0.3-10 keV flux is (1.4+/-0.2) x10^-12 erg cm^-2 s^-1. The flux observed is a factor of about 3 higher than that previously observed by XRT on 10 January 2009, (0.5+/-0.1) x10^-12 erg cm^-2 s^-1. Simultaneous Swift/UVOT data collected in the UVW2 filter show that the UV flux increased rapidly throughout this observation, brightening by 1 mag over a 24 hour period up to a maximum of 14.4 mag. This peak is about 3.4 mag brighter than during the UVOT observations performed on 10 January 2009. A similar behaviour could be detected in ATOM R-band observations performed on 28 October, with an increase by about 0.7mag during the same time scale. This Swift follow-up confirms that the blazar has brightened in the X-ray and UV bands following the optical and GeV flare. A brightening of the source also in NIR was reported by Carrasco et al.(ATel #2977). In consideration of the ongoing activity of this source, we encourage further multiwavelength observations. We thank the Swift team for their rapid scheduling of these observations.