Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ S4 1726+45
ATel #14144; R. Angioni (SSDC/INFN)
on 3 Nov 2020; 22:52 UT
Credential Certification: Roberto Angioni (r.angioni90@gmail.com)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
Referred to by ATel #: 14162
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 (FSRQ) S4 1726+45, also known as 4FGL J1727.4+4530 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 261.865212 deg, Decl. = +45.511036 deg (J2000; Johnston et al. 1995, AJ, 110, 880), and redshift z=0.717 (Henstock et al. 1997 MNRAS, 290, 380).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 2 November 2020, with a daily averaged gamma-ray flux (E>100MeV) of (1.0+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). The latter corresponds to a flux increase of a factor of about 20 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). This is the highest LAT daily flux ever observed for this source. The corresponding photon index is 2.6+/-0.2, and is consistent the 4FGL value of 2.48+/-0.02 within the uncertainties.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is being added to the "LAT Monitored Sources" and consequently, a preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT will be publicly available (http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/). We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Roberto Angioni (roberto.angioni@ssdc.asi.it).
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.
