Fermi-LAT detection of renewed gamma-ray activity from the FSRQ 4C +27.50
ATel #15746; G. La Mura (LIP, Portugal), on behalf of the Fermi Large Area Telescope Collaboration
on 6 Nov 2022; 22:23 UT
Credential Certification: Giovanni La Mura (glamura@lip.pt)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed renewed activity from a source positionally consistent with the FSRQ 4C +27.50, also known as 4FGL J2321.9+2734 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 350.49943 deg, Decl. = +27.54623 deg (J2000; Johnston et al. 1995, AJ, 110, 880), and redshift z = 1.253 (Stickel & Kuehr 1992, A&A, 264, 68).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on November 5, 2022, with a daily averaged gamma-ray flux (E>100MeV) of (2.1+/-0.3) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of more than 150 with respect to the average value reported in the third release of the Fourth Fermi-LAT source catalogue (4FGL-DR3, Abdollahi et al. 2022, ApJS, 260, 53). The corresponding photon index is 2.22+/-0.11, and is consistent with the catalogue spectral index of 2.22+/-0.04, similarly to what has been previously observed (ATel #15549). To date, this is the highest gamma-ray flux observed from this source by LAT on a daily time-scale.
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 list of LAT daily monitored sources. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Giovanni La Mura (glamura AT lip DOT pt).
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.
