Fermi-LAT detection of enhanced gamma-ray activity from blazar S5 1217+71
ATel #16486; Federica Giacchino (INFN Roma Tor Vergata & SSDC) on behalf of the Fermi Large Area Telescope Collaboration
on 26 Feb 2024; 21:11 UT
Credential Certification: Federica Giacchino (federica.giacchino@roma2.infn.it)
Subjects: Gamma Ray, >GeV, AGN, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed gamma-ray flaring activity from a source positionally consistent with the flat spectrum radio quasar S5 1217+71, also known as TXS 1217+713 and 4FGL J1220.1+7105 in the fourth Fermi catalog (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with J2000.0 VLBI coordinates R.A: 185.0438 deg, Dec.: +71.092 deg (Petrov et al. 2005, AJ, 129, 1163). This blazar has redshift z=0.451 (Stickel & Kuehr 1996, A&AS, 115, 1).
Preliminary analysis indicates that on 2024 February 24, S5 1217+71 was in a high state with a daily average gamma-ray flux (E>100MeV) of (0.9 +/- 0.1) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 30 times greater than the average flux reported in the 4FGL catalog. This is the greatest flux that has been detected for this source by the Fermi LAT. The corresponding photon index is 2.06 +/- 0.12, corresponding to a harder spectrum than the 4FGL value of 2.32 +/- 0.02. The Fermi-LAT Collaboration previously announced flaring gamma-ray activity from it on March 13, 2013 (ATel #4885).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of these sources will continue. In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations. For these sources the Fermi LAT contact person is Federica Giacchino (federica.giacchino@roma2.infn.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.
