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Optical follow-up of B2 1308+32

ATel #6072; R. Nesci (INAF/IAPS, Roma), A. Caravano, L. Villani (Oss. Cittadino, Foligno)
on 15 Apr 2014; 22:42 UT
Credential Certification: Roberto Nesci (Roberto.Nesci@iaps.inaf.it)

Subjects: Optical, AGN, Blazar

Following the indication of enhanced Gamma-ray luminosity of the QSO B2 1308+32 (ATel #6068) we performed optical photometry of the source with the 30 cm telescope of the Foligno Observatory and a Canon 350D camera on 2014 April 15.90. The instrumental response of the camera is peaked in the Johnson V band. Twenty three comparison stars were taken from the UCAC 4 catalog, ranging from V=12.5 to 16.6. A linear fit of our instrumental vs catalog magnitudes has an rms deviation of 0.07 mag. The QSO was barely detectable in our images, at V=17.3 +/-0.4 mag. In the past this source has been detected at very different flux levels: our photometry of the Palomar QuickV survey plate (1983) gives V=15.8 in the UCAC 4 scale; literature data range from V=14.8 (O'Dell et al. 1978, ApJS 38, 267) and V=19.7 (Ojha et al. 2009, AJ 138, 845), with the source being generally at low flux levels. Our value must therefore be considered as an intermediate flux level. The Gamma-ray flux increase of a factor 13 w.r.t. the average level of the past 3 years, reported by Buson et at. in ATel #6068, does not seem therefore to have a comparable (3 magnitudes) flux increase in the optical band. Further optical follow-up is encouraged.