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Swift follow-up confirms the high activity state of CGRaBS J1848+3219

ATEL # 2963; F. D'Ammando (INAF-IASF Palermo), K. V. Sokolovsky (MPIfR/ASC Lebedev) on behalf of the Fermi Large Area Telescope Collaboration and J. Gelbord (PSU)
on 21 Oct 2010; 15:59 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Filippo D'Ammando (

Subjects: Optical, Ultra-Violet, X-ray, Gamma Ray, >GeV, Request for Observations, AGN, Quasars

Following the gamma-ray flare of CGRaBS J1848+3219 (also known as B2 1846+32A and 1FGL J1848.5+3224; Abdo et al. 2010, ApJS 188, 405) detected by Fermi LAT on October 18, 2010 (ATel #2954, Donato et al. 2010) we performed a Swift target of opportunity observation on October 19.

Swift/XRT data were taken in Photon Counting mode for a total exposure of 4.4 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 = 9.45 x10^20 cm^-2, Kalberla et al. 2005) and a photon index of 1.60+/-0.18. The corresponding unabsorbed 0.3-10 keV flux is (4.3+/-0.6) x10^-12 erg cm^-2 s^-1. The flux observed is a factor of 5 higher than that previously observed by XRT on February 20, 2009 (8.6+/-1.2 x10^-13 erg cm^-2 s^-1) with a similar photon index of 1.64+/-0.18.

Simultaneous Swift/UVOT observations found CGRaBS J1848+3219 about 3.2 mag brighter in V-band and 2.7 mag brighter in W2-band compared to the UVOT observations performed on February 20, 2009.

Band 2010-10-19 2009-02-20
V 15.47+/-0.03 18.70+/-0.09
B 15.95+/-0.02 19.21+/-0.05
U 15.30+/-0.02 18.51+/-0.04
W1 15.54+/-0.02 18.41+/-0.04
M2 15.72+/-0.02 18.39+/-0.04
W2 15.85+/-0.03 18.58+/-0.03

In consideration of the ongoing activity of this source, confirmed also by the Swift observations, we strongly encourage further multiwavelength observations. For this source the Fermi LAT contact person is D. Donato (

We thank the Swift Team for their rapid scheduling of this observation.

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