NIR follow-up of PKS 0208-512

ATel #3421; R. Nesci (Univ. La Sapienza), M. Kadler (Dr. Remeis Sternwarte), R. Ojha (US Naval Obs.), T. Pursimo (NOT, La Palma), G. Tosti (Univ. Perugia), J. Blanchard and J. Lovell (Univ. Tasmania).
on 10 Jun 2011; 09:33 UT
Credential Certification: Roberto Nesci (roberto.nesci@uniroma1.it)

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The source PKS 0208-512 is being monitored by the TANAMI project (http://pulsar.sternwarte.uni-erlangen.de/tanami/) in NIR with the REM telescope (http://www.rem.inaf.it). The source underwent a Gamma Ray flare detected by Fermi-LAT on May 11, 2011 (JD 55690, Atel #3338) when the source was not observable from the ground. We recorded J=15.68 (+/-0.14) on JD 55660 (one month before the Gamma-ray flare) using a sequence of 10 comparison stars taken from the 2MASS for differential photometry: this value is in agreement with the SMARTS data (http://www.astro.yale.edu/smarts/glast/index.html). We observed the source quite brighter, at J=14.81 (+/-0.08) on JD 55716 (26 days after the gamma-ray flare): magnitudes in the other NIR bands were H=14.02 ±0.14 and K=13.28 ±0.20, giving colors similar to those reported in the 2MASS point source catalogue (Cutri et al. 2003) and typical of a BL Lac object. It is therefore likely that the Gamma-ray flare had an optical counterpart, as e.g. in the case of CGRaBS J0211+1051 (ATel #3127). Radio monitoring at a frequency of 6.7 GHz with the Ceduna radio telescope in South Australia shows no evidence for any activity up to now (http://www-ra.phys.utas.edu.au/~jayb/ced/agn/B0208-512.png). Further observations are encouraged.