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ASAS-SN optical light-curve of blazar TXS 0506+056, located inside the IceCube-170922A error region, shows increased optical activity

ATel #10794; A. Franckowiak (DESY), K. Z. Stanek, C. S. Kochanek, T. A. Thompson (OSU), T. W.-S. Holoien, B. J. Shappee (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), Subo Dong (KIAA-PKU)
on 28 Sep 2017; 18:00 UT
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

Subjects: Optical, Blazar

Referred to by ATel #: 10799, 10817, 10830, 10831, 10838, 10840, 10844, 10861

Archival ASAS-SN (Shappee et al. 2014) data show an increased optical activity of the blazar TXS 0506+056, which is located inside the error region of the high-energy neutrino candidate IceCube-170922A, and was found to be in a flaring state by Fermi-LAT (ATel #10791), and it was also observed by Swift 10792).

Using ASAS-SN Sky Patrol public all-sky light curve interface (Kochanek et al. 2017), we retrieved 200-day light curve of TXS 0506+056, showing a rise of ~0.5 mag in V-band over the last 50 days. Proximity to the Sun prevented observations between April and July 2017. In earlier observations the source was at a low state with V-band magnitude of ~14.7. V-band magnitudes are calculated in real-time using aperture photometry, with zero-points calibrated using the APASS catalog. ASAS-SN images have 8" pixels (~15" FWHM PSF,) so blending/crowding might be significant in some cases (but most likely not very significant in this case).

We also retrieved the entire ASAS-SN light curve of TXS 0506+056, starting in October 2012, and while it shows significant variability, the recent data are the brightest this object has been in several years.

We thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, and the Chinese Academy of Sciences South America Center for Astronomy (CASSACA).