Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ GB6 J0342+3858
ATel #15900; Denis Bernard (LLR, Ecole Polytechnique & CNRS / IN2P3), Janeth Valverde (UMBC / NASA GSFC), on behalf of the Fermi Large Area Telescope Collaboration
on 13 Feb 2023; 13:01 UT
Credential Certification: Denis Bernard (Denis.bernard@in2p3.fr)
Subjects: >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 GB6 J0342+3858 (also known as 4FGL J0342.2+3858), with coordinates R.A. = 55.567788 deg, Decl. = 38.985075 deg (J2000; Jackson, N., et al. 2007, MNRAS, 376, 371), and redshift z=0.945 (Makarov, V. V., et al. 2019, ApJ, 873, 132).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 2023 February 11 from 12:00 - 18:00 UTC, with an averaged gamma-ray flux (E>100MeV) of (0.6+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 100 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL-DR3, Abdollahi, S., et al. for the Fermi-LAT collaboration 2022, ApJS, 260, 53). This is the highest LAT daily flux ever observed for this source. The corresponding photon index is 2.01+/-0.19, and is smaller than the 4FGL-DR3 value of 2.26+/-0.11.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. Preliminary Fermi-LAT light curves 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_J0342.2+3858. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Denis Bernard (denis.bernard@in2p3.fr).
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.
