Optical flare observed in the flaring gamma-ray QSO TXS 0646-176
ATel #12293; Tapio Pursimo (NOT), Anlaug A. Djupvik (NOT), and Roopesh Ojha (NASA/GSFC/UMBC)
on 14 Dec 2018; 01:08 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)
Subjects: Optical, Gamma Ray, >GeV, Blazar, Quasar
We report optical photometry of the QSO TXS 0646-176, obtained with the 2.56m Nordic Optical Telescope in La Palma, to look for any enhanced optical activity associated with a recent flare in the daily averaged gamma-ray flux (ATel#12252).
These NOT observations were made using the ALFOSC (Alhambra Faint Object Spectrograph and Camera) instrument at the epoch 2018-12-09T01:24. Standard IRAF data reduction (de-biasing + flat field correction with twilight flats) was carried out and differential photometry was performed. The brightness was calibrated against 54
SDSS field stars near the target. The std-dev of the zero point was 0.04 mag.
We find that TXS 0646-176 had an SDSS r-magnitude = 17.45+/-0.04 (AB-system). This result suggests that there is significant enhancement in its optical magnitude. For example, an historic value of this object's r-magnitude from PanSTARRS at mean epoch 09-31-2013 is 19.0835 (Chambers et al. 2016, arXiv:1612.05560). It has reported SDSS magnitudes of 18.82 and 18.58 in DR8 (Aihara et al. 2011, ApJS, 193, 29) and 18.84 in DR7 (Abazajian et al. 2009, ApJS, 182, 543). The source has GSC2.3 F (Rmag ) of 19.1.
We encourage further multi-wavelength coverage. We will continue to monitor this source and report future developments using this and other platforms.
