Fermi-LAT detection of renewed gamma-ray activity from the FSRQ OP 313
ATel #16497; Chiara Bartolini (University of Trento & INFN Bari) on behalf of the Fermi Large Area Telescope Collaboration
on 1 Mar 2024; 11:26 UT
Credential Certification: Janeth Valverde (valverde@llr.in2p3.fr)
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 enhanced gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar (FSRQ) OP 313 (B2 1308+32), also known as 4FGL J1310.5+3221 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 197.619432 deg, Decl. = +32.345495 deg (J2000; Johnston et al. 1995, AJ, 110, 880), and redshift z=0.997 (Schneider et al. 2010, AJ, 139, 2360).
Preliminary analysis indicates that this source was in an elevated and hard gamma-ray emission state during the past week with a maximum on February 27, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (3.1+/-0.4) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 60 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 1.8+/-0.1, indicating a significantly harder spectrum than the 4FGL photon index of 2.34+/-0.02. The last time that the Fermi-LAT Collaboration announced flaring gamma-ray activity from OP 313 was December 1, 2023 (Atel #16356).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of these sources will continue. A preliminary light curve for OP 313 can be accessed via the Fermi-LAT Light-Curve Repository at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1310.5+3221. We encourage multifrequency observations of this source. For OP 313, the Fermi-LAT contact person is Sara Buson (sara.buson at uni-wuerzburg.de).
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.
