A new gamma-ray flaring episode of the FSRQ S4 0954+65
ATel #14426; Giacomo Principe (University of Trieste and INFN - Trieste, INAF - Istituto di Radioastronomia, Bologna) on behalf of the Fermi-LAT Collaboration
on 28 Feb 2021; 18:53 UT
Credential Certification: Giacomo Principe (giacomo.principe@inaf.it)
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed a new flaring episode from a source positionally consistent with the FSRQ S4 0954+65 (RA: 149.696855, Dec: +65.565227, J2000, Johnston et al., 1995, AJ, 110, 880) at z = 0.368 (Wills et al., 1992, ApJ, 398, 454).
Preliminary analysis indicates that this source was in a flaring state on 2021 February 27, with a daily averaged gamma-ray flux (E>100MeV) of (0.7+/-0.2) X 10^-6 photons cm^-2 s^-1 (uncertainties are statistical only), and a peak 6-hr flux of (1.1+/-0.3) X 10^-6 photons cm^-2 s^-1 from 12:00-18:00 UTC. The former corresponds to a flux increase of a factor of 15 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). This is the second flaring episode of this source, with flux values similar to those reported on 2014 November 17 (ATel #6709). The corresponding daily photon index is 2.1+/-0.2, and is compatible with the 4FGL value.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source has been 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 (https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/S4_0954p65). We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Felicia Krauss (felicia.krauss@psu.edu ).
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.
