Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ 5C 12.291
ATel #14311; C. C. Cheung (NRL), S. Buson (Univ. Wuerzburg), on behalf of the Fermi Large Area Telescope Collaboration
on 11 Jan 2021; 15:02 UT
Credential Certification: Teddy Cheung (Teddy.Cheung@nrl.navy.mil)
Subjects: Gamma Ray, >GeV, Blazar
Referred to by ATel #: 14534
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar 5C 12.291 (a.k.a., MG2 J130822+3546; Benn et al. 1984, MNRAS 209, 683; Langston et al. 1990, ApJS 72, 621), also known as 4FGL J1308.5+3547 (The Fermi-LAT collaboration 2020, ApJS, 247, 33; see also 4FGL-DR2, Ballet et al. 2020, arXiv:2005.11208), with coordinates R.A. = 197.0987879 deg, Decl. = +35.7769900 deg (J2000; Fomalont et al. 2003, AJ 126, 2562), and redshift z=1.055 (Vermeulen et al. 1996, AJ 111, 1013).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 2021 January 8, with a daily averaged gamma-ray flux (E>100MeV) of (6.0+/-1.4) X 10^-7 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 70 relative to the 10-year average flux reported in the 4FGL-DR2. This is the highest LAT daily flux ever observed for this source. The corresponding photon index is 2.1+/-0.2, and is marginally smaller than the 4FGL-DR2 value of 2.37+/-0.05.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. For this source the Fermi LAT contact person is C. C. Cheung (Teddy.Cheung at nrl.navy.mil).
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.
