Fermi LAT detection of a GeV flare from PMN J1303-5540
ATel #16689; S. Wagner (University of Wuerzburg), J. Valverde (UMBC/NASA GSFC), I. Mereu (INFN Perugia); on behalf of the Fermi Large Area Telescope Collaboration
on 5 Jul 2024; 06:28 UT
Credential Certification: Janeth Valverde (valverde@llr.in2p3.fr)
Subjects: Gamma Ray, >GeV, VHE, Request for Observations, AGN, Blazar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flux from a source positionally consistent with blazar PMN J1303-5540, also known as 4FGL J1304.0-5539 in the fourth Fermi-LAT catalog Data Release 4 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 196.164 deg, Decl. = 55.595 deg (J2000, Massardi et al. 2008, MNRAS, 384, 775).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on 2024 July 2, with a daily average gamma-ray flux (E>100MeV) of (1.27 +/- 0.22) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of about a factor of 80 relative to the average flux of 1.6 x 10^-8 photons cm^-2 s^-1 reported in the 4FGL-DR4. This is the highest LAT daily flux ever observed for this source. The corresponding single power law photon spectral index is 2.21 +/- 0.13, which indicates a harder/flatter spectrum than the 4FGL-DR4 value of 2.73 +/- 0.11.
Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is being added to the "LAT Monitored Sources" and consequently, a preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT will be publicly available at http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/. We encourage multiwavelength observations of this source. For this source, the Fermi-LAT contact person is Sarah Wagner (sarah.wagner@uni-wuerzburg.de) and Janeth Valverde (valverde@llr.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.
