Fermi-LAT detection of a possible gamma-ray flaring from the flat spectrum radio source B2 2125+35
ATel #16590; Federica Giacchino (INFN Roma2 & SSDC), Isabella Mereu (INFN Perugia ), on behalf of Fermi Large Area Telescope Collaboration
on 16 Apr 2024; 18:58 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 for the first time from a source positionally consistent with the flat spectrum radio source B2 2125+35, also known as 4FGL J2127.7+3612 in the fourth Fermi catalog (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with radio coordinates (J2000.0) R.A: 321.92922 deg, Dec.: +36.218278 deg (Healey S. et al. 2007, ApJS,171,61H). The radio source is a likely blazar with an unknown redshift.
Preliminary analysis indicates that on 2024 April 14, B2 2125+35 was in a high state with a daily average gamma-ray flux (E>100MeV) of (0.7 +/- 0.2) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 115 times greater than the average flux reported in the 4FGL catalog. The measured photon index is 2.29 +/- 0.22, consistent within uncertainties with the 4FGL value of 1.99 +/- 0.04.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of these sources will continue. In consideration of the ongoing activity of this source we strongly encourage multi wavelength observations. The gamma-ray flat spectrum radio source B2 2125+35 light curve repository is in https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J2127.7+3612 For these sources 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.
