The gamma-ray flaring blazar TXS 0025+197 observed below R=16 in optical

ATel #13910; Alessandro Marchini (Astronomical Observatory, Department of Physical Sciences, Earth and Environment (DSFTA), University of Siena - Italy), Giacomo Bonnoli, Lorenzo Bellizzi, Stefano Menchiari, Vincenzo Millucci, Riccardo Paoletti, Leonardo Stiaccini, Stefano Truzzi, Sofia Ventura, Carolin Wunderlich (DSFTA, University of Siena - Italy), Massimo Conti, Massimo Damiani, Claudio Vallerani (Astronomical Observatory, University of Siena - Italy).
on 31 Jul 2020; 11:55 UT
Credential Certification: Giacomo Bonnoli (giacomo.bonnoli@unisi.it)

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We observed on July the 30th the Flat Spectrum Radio Quasar TXS 0025+197 (RA: 00 27 29.8 Dec: +20 00 27 J2000.0) at redshift z=1.55 (Alam et al., 2015, ApJS, 219, 12) from the Astronomical Observatory of the University of Siena. We had already visited this source (see ATels #13038,#13370) in the framework of our program dedicated to blazars that, being either established or potential emitters of very high energy (VHE, E > 30 GeV) gamma rays, are potential targets for the MAGIC Telescopes. Our observation was triggered by recent ATel #13860 posted on 2020 July, the 10th, by Isabella Mereu on behalf of the Fermi Large Area Telescope Collaboration, reporting renewed gamma-ray activity from this blazar. Our observations consist of 9 x 300 s exposures in the Johnson-Cousins R, taken in 2x2 binning with clear sky in dark conditions. 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 (including also the ones already reported in our previous ATels #13038,#13370) are reported in the following table:

Civil Date (UT) Rmag(dRmag)
2019 Aug 16.11 17.06(0.03)
2019 Aug 17.04 16.76(0.03)
2019 Aug 19.13 16.78(0.04)
2019 Nov 30.73 16.25(0.02)
2019 Dec 10.72 17.05(0.06)
2019 Dec 21.72 16.86(0.05)
2019 Dec 23.74 16.73(0.02)

2020 Jul 30.10 15.98(0.02)


Quoted uncertainty is statistical only. The magnitude R=15.98(0.02) measured duting last visit is unprecedented in our sampling, and around 35 times brighter than the reference value R=19.9 derived from the SIMBAD Astronomical Database publicly available at http://simbad.u-strasbg.fr/simbad (see our ATel #13038 for details). 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 our 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