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Optical brightening of the flaring blazar TXS 0025+197

ATel #13038; 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 17 Aug 2019; 16:41 UT
Credential Certification: Giacomo Bonnoli (giacomo.bonnoli@unisi.it)

Subjects: Optical, AGN, Blazar

Referred to by ATel #: 13045, 13370, 13910

In the last two nighs we observed 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. Our interest was triggered by ATel #13032 reporting a flare in gamma rays detected by the Large Area Telescope onboard the Fermi satellite.
Our observations consist of 12 x 300 s exposures in the Johnson-Cousins R filter, taken in 2x2 binning with clear sky during full moon. 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 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)


Quoted uncertainty is statistical only. A reference magnitude R~19.9 can be derived, with some caveats, from r and g magnitudes reported in SIMBAD http://simbad.u-strasbg.fr/simbad/ and taken from SDSS DR12 (see Paris et al., A&A, 597A, 79-79, 2012) by means of a conversion formula among the two photometric systems obtained by Lupton (2005). Assuming this reference, the current enhancement factor for the optical flux is of the order of 20. 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