Unprecedented optical state of the flaring blazar B2 1420+32

ATel #12886; 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 25 Jun 2019; 18:17 UT
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Credential Certification: Giacomo Bonnoli (giacomo.bonnoli@unisi.it)

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We observed last night 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, in the context of our monitoring of potential TeV blazars in support of the MAGIC Collaboration.

B2 1420+32 was already observed in active state at infrared wavelengths two weeks ago (see ATel #12866). 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 and at high elevation above the horizon. After dark current subtraction and flat field correction the images for each night 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 recent 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)


Quoted uncertainty is statistical only. To the best of our knowledge the bright magnitude in the R band measured last night, corresponding to a flux density around 1.0e-11 erg cm^-2 s^-1 at the 0.64 um effective wavelength of the filter, is unprecedented for this source (see also ATel #11110,#12201,#12379 for previous flaring episodes in the optical-IR). If compared to the value R=19.11 (Healey et al., 2008, ApJSS, 175, 97) reported in SIMBAD http://simbad.u-strasbg.fr/simbad/ it implies an enhancement in the observed flux of more than 30 times at these wavelengths. 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