Fermi-LAT detection of renewed gamma-ray activity from the FSRQ S5 0633+73
ATel #16868; Chiara Bartolini (University of Trento & INFN Bari) on behalf of the Fermi Large Area Telescope Collaboration
on 20 Oct 2024; 07:53 UT
Credential Certification: Chiara Bartolini (chiara.bartolini-1@unitn.it)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar
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 S5 0633+73, also known as 4FGL J0638.6+7320 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 99.841505 deg, Decl. = 73.416122 deg (J2000; Xu et al., 2019 ApJ, 242, 5), and redshift z=1.85 (Henstock et al., 1997 ApJ, 290, 380).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on October 17, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (9.6 +/- 1.6) X 10^-7 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 75 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 2.7 +/- 0.2 and is consistent with than the 4FGL value of 2.8 +/- 0.1. The source flux remained high state on October 18, 2024.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for S5 0633+73 can be accessed via the Fermi-LAT Light Curve Repository at
