The flaring blazar B2 1420+32 below R=14

ATel #12914; Alessandro Marchini (Astronomical Observatory, Department of Physical Sciences, Earth and Environment (DSFTA), University of Siena - Italy), Giacomo Bonnoli, Lorenzo Bellizzi, Vincenzo Millucci, Riccardo Paoletti, Leonardo Stiaccini, Stefano Truzzi, Sofia Ventura (DSFTA, University of Siena - Italy), Massimo Conti, Claudio Vallerani (Astronomical Observatory, University of Siena - Italy).
on 9 Jul 2019; 10:26 UT
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Credential Certification: Giacomo Bonnoli (giacomo.bonnoli@unisi.it)

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We continued monitoring the Flat Spectrum Radio Quasar B2 1420+32 (RA: 14 22 30.38 Dec: +32 23 10.44 J2000.0) at redshift z=0.682 (Hewett & Wild, 2010, MNRAS, 405, 2302) from the Astronomical Observatory of the University of Siena, after our ATel #12886 reporting its unprecedented optical state (see also ATel #12887).
Our observations consist of 3 x 300 s exposures in the Johnson-Cousins R filter, taken in 2x2 binning under good observing conditions with clear sky. After dark current subtraction and flat field correction the images for each visit were averaged and aperture photometry was performed on the average frame by means of the MaximDL software package. Reference and check stars in the field of view were selected from the APASS9 (Henden et al., 2016) catalogue. The reference R magnitudes were derived from those reported in the same APASS9 catalogue after conversion between the two different photometric systems, following a formula taken from Munari U., "Classical and Recurrent Novae", JAAVSO, 40 (2012). The results of our observations of this source are gathered in the following table:

Civil Date (UT) Rmag(dRmag)
2019 Feb 15.21 17.12(0.09)
2019 Jun 24.91 15.30(0.02)
2019 Jun 25.88 14.49(0.03)
2019 Jun 26.86 15.42(0.08)
2019 Jun 27.85 15.32(0.03)
2019 Jun 29.88 15.17(0.03)
2019 Jun 30.84 15.23(0.04)
2019 Jul 01.02 15.25(0.03)
2019 Jul 01.86 14.48(0.03)
2019 Jul 02.02 14.21(0.03)
2019 Jul 02.85 14.56(0.03)
2019 Jul 03.02 14.43(0.03)
2019 Jul 03.88 14.49(0.03)
2019 Jul 08.83 13.70(0.03)


Quoted uncertainty is statistical only. If compared to the value R=19.11 (Healey et al., 2008, ApJSS, 175, 97) reported in SIMBAD http://simbad.u-strasbg.fr/simbad/ the R=13.7 measurement from last night implies an enhancement in the observed flux of a factor greater than 100. This traslates into an intrinsic flux density around 4.8e-11 erg cm^-2 s^-1 at the 0.64 um effective wavelength of the filter. We will continue monitoring the source in the following nights. Multi-wavelength follow-up is encouraged.

Any enquiry on these observations can be addressed either to Alessandro Marchini (alessandro.marchini@unisi.it) or to Giacomo Bonnoli (giacomo.bonnoli@unisi.it).

We acknowledge excellent scientific cooperation with, and valuable support from, the WEBT Collaboration, the Tuorla Observatory and the MAGIC Collaboration.
A brief description of the instrumental setup is available at the official webpage of the Astronomical Observatory of the University of Siena (see link below).

Astronomical Observatory of the University of Siena - Official Webpage