Fermi LAT detection of increasing gamma-ray activity from flat spectrum radio quasar PMN J0643+0857
ATel #16429; Federica Giacchino (INFN Roma Tor Vergata & SSDC) on behalf of the Fermi Large Area Telescope Collaboration
on 5 Feb 2024; 06:54 UT
Credential Certification: Federica Giacchino (federica.giacchino@roma2.infn.it)
Subjects: Gamma Ray, >GeV, AGN, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed gamma-ray flaring activity from a source positionally consistent with the flat spectrum radio source PMN J0643+0857, also known as 4FGL J0643.3+0857 (Abdollahi et al. 2022, ApJS, 260, 53), with VLBI coordinates (J2000.0) R.A.: 100.8345 deg., Dec: 8.9525 deg. (L. Petrov et al. 2006 AJ 131, 1872). The source has a redshift z=0.88 (Ajello, M. et al. 2022, ApJS, 263, 24A).
Preliminary dedicated analysis indicates that on February 2, 2024, PMN J0643+0857 reached a daily gamma-ray flux (E>100MeV) of (2.1+/- 0.4) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 40 times greater than the average flux reported in the four Fermi-LAT catalog (4FGL, Abdollahi et al. 2020, ApJS, 247, 33). The corresponding photon index is 2.55+/-0.03, indicating a slightly harder state than the 4FGL-DR3 value of 2.66.
Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source we encourage multiwavelength observations. The flat spectrum radio quasar PMN J0643+0857 is one of the "LAT Monitored Sourcesâ (https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J0643.3+0857). For this source the Fermi LAT contact person is Federica Giacchino (federica.giacchino@roma2.infn.it).
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.
