Optical follow-up of 4C+28.07

ATel #3672; R. Nesci, S. Sclavi (University La Sapienza, Roma, Italy)
on 7 Oct 2011; 08:07 UT
Credential Certification: Roberto Nesci (roberto.nesci@uniroma1.it)

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Prompted by the ATel #3670 we observed the blazar 4C +27.08 with the TACOR telescope of the Department of Physics at La Sapienza University on 2011-10-06 UT 21:30, under a veiled sky. An Apogee U2 CCD camera was used with a standard R (Cousins) filter. About 80 images of 30s exposure each were taken, in sequences of 20 images with slightly different sky pointing, to ensure that possible hot pixels do not fall always on the same star. Individual images were than dark subtracted and flat fielded. A sequence of 8 nearby stars were selected from the GSC2.3 catalogue, using the F magnitudes as a proxy for the R filter, ranging from mag 11.86 to 15.87. A linear fit between instrumental and nominal magnitudes gave very good results (slope 0.99, rms 0.07 mag). The source was detected at R=16.5 +-0.2, which is brighter than the value 16.99 reported in the same GSC2.3 catalogue (based on POSS II plate), and definitely brighter than the value (about 20) derived from the POSS I digitized plate. Further follow-up will be made if weather conditions will allow.