Fermi-LAT detection of renewed gamma-ray activity from the FSRQ TXS 2013+370
ATel #16327; Adithiya Dinesh, (Universidad Complutense de Madrid) and Denis Bernard (LLR, Ecole Polytechnique & CNRS / IN2P3), on behalf of the Fermi Large Area Telescope Collaboration
on 7 Nov 2023; 20:38 UT
Credential Certification: Denis Bernard (Denis.bernard@in2p3.fr)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
Referred to by ATel #: 16465
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed renewed gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar TXS 2013+370, also known as MG2 J201534+3710 and 4FGL J2015.5+3710 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 303.869708 deg, Decl. = 37.183198 deg (J2000; Fomalont et al. 2003, AJ, 126, 2562), and redshift z=0.859 (Shaw et al. 2013, ApJ, 764, 135).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on November 6, 2023, with a daily averaged gamma-ray flux (E>100MeV) of (1.6 +/- 0.4) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 13 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 2.16 +/- 0.14 and is slightly harder than the 4FGL value of 2.45 +/- 0.02 within the uncertainties. The source is undergoing an increase in flux since November 1, 2023. Enhanced activity of TXS 2013+370 in LAT observations was previously reported in 2020 (ATel 14252).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Adithiya Dinesh (adinesh@ucm.es).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
