Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PMN J1903-6749
ATel #15362; G. La Mura (LIP, Portugal), on behalf of the Fermi Large Area Telescope Collaboration
on 4 May 2022; 18:43 UT
Credential Certification: Giovanni La Mura (glamura@lip.pt)
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 PMN J1903-6749, also known as 4FGL J1902.9-6748 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 285.75512 deg, Decl. = -67.82556 deg (J2000; Healey et al. 2008, ApJS, 175, 97), and redshift z = 0.254 (Massaro et al. 2015, ApJS, 217, 2).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on May 3, 2022, with a daily averaged gamma-ray flux (E>100MeV) of (0.9+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 30 relative to the average flux reported in the second data release of the fourth Fermi-LAT catalog (4FGL-DR2). This is the highest LAT daily flux ever observed for this source. The corresponding photon index is 2.07+/-0.15, and is smaller than the 4FGL value of 2.44+/-0.03, as opposed to what has been previously observed (see ATel #13767). The spectral hardening is further confirmed by the detection of a high-energy photon, with E = 15 GeV, which has an estimated probability p = 0.99989 of being associated with the source and was observed at 22:44:08 UT of May 3, 2022.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. The light curve of this source can be consulted through the Fermi-LAT Light Curve Repository (LCR) at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1902.9-6748. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Giovanni La Mura (glamura@lip.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.
