Optical follow-up of 1FGL J0211.2+1049

ATel #3127; R. Nesci (University La Sapienza, Roma Italy)
on 27 Jan 2011; 23:07 UT
Credential Certification: Roberto Nesci (roberto.nesci@uniroma1.it)

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Prompted by Atel #3120 of a strong Gamma-ray flare of the BL Lac object CGRaBS J0211+1051, we observed it on January 27.87 2011 with the 23 cm telescope on top the Department of Physics of La Sapienza University with an R_C filter and an Apogee U2 CCD camera. Eight comparison stars were taken from the GSC2.3 catalogue to define the source magnitude. The source appeared at R_C=13.37, definitely brighter that the historical GSC2.3 value of 15.11, based on the POSS I (year 1950) red plate. Another historical value (year 1971) can be derived from the Digitized First Byurakan Survey (DFBS) at R= 14.7, which is R=15.1 converted onto the GSC2.3 magnitude scale using the same comparison sequence. We have therefore an indication that the strong Gamma-ray flare of January 23 had an optical counterpart.