Swift XRT/UVOT follow-up of the gravitationally lensed blazar S3 0218+35 after a gamma-ray flare

ATel #4351; D. Donato (NASA/GSFC), C. C. Cheung (NRC/NRL), S. Ciprini (ASI ASDC & INAF OAR, Rome); on behalf of the Fermi Large Area Telescope Collaboration
on 1 Sep 2012; 20:22 UT
Credential Certification: Teddy Cheung (ccheung@milkyway.gsfc.nasa.gov)

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Following the Fermi-LAT detection of a developing GeV flare in the period 2012 August 22-26 from the gravitationally lensed blazar S3 0218+35 (ATEL #4343), Swift observations were obtained on August 28 and 30 (5 ks exposures). These observations confirm that the blazar is also in a relatively high X-ray state in comparison to previous Swift observations obtained on 2008 December 12 (2.9 ks) and 2010 August 20 (2.3 ks).

The blazar is well detected in each XRT observation with 0.3-10 keV count rates of 0.027 +/- 0.003 (August 28) and 0.029 +/- 0.003 cts/s (August 30) indicating no significant variability between the two days. The count rates are about 50% larger than in the previous XRT observations obtained in 2008 (0.018 +/- 0.003 cts/s) and 2010 (0.019 +/- 0.003 cts/s). Combining the two 2012 August observations, the data are well fit (reduced chi-square = 0.76 for 18 degrees of freedom) by a power law with a photon index, Gamma = 1.25 +/- 0.17, and an observed 0.3-10 keV flux = 1.40 (+/- 0.11) e-12 erg/cm2/s (1.48e-12 erg/cm2/s, unabsorbed) assuming Galactic NH = 5.6e20 cm-2.

In the 2012 August data, the blazar is detected with the UVOT in the V-band with an average magnitude = 19.9 +/- 0.4 with no significant variability observed between the observations spanning two days.

In consideration of the recent activity of this source we encourage further multiwavelength observations. For this source the Fermi LAT contact person is Teddy Cheung (ccheung@milkyway.gsfc.nasa.gov).

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