Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PMN J0721+0406
ATel #16893; Adithiya Dinesh (Universidad Complutense de Madrid), on behalf of the Fermi Large Area Telescope Collaboration
on 3 Nov 2024; 16:09 UT
Credential Certification: Giovanni La Mura (glamura@lip.pt)
Subjects: Gamma Ray, 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 enhanced gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar PMN J0721+0406, also known as 4FGL J0721.3+0405 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 110.34962 deg, Decl. = +4.11228 deg (J2000; Hunt et al. 2021, AJ, 162, 121H), and redshift z=0.665 (Shaw et al. 2012, ApJ, 748, 49).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on November 1, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (0.5+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 20 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 2.18+/-0.21, indicating a significantly harder spectrum than the 4FGL value of 2.57+/-0.04.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for PMN J0721+0406 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_J0721.3+0405. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Adithiya Dinesh (adinesh@ucm.es).
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.
