Fermi LAT detection of a possible gamma-ray flaring from the flat spectrum radio source 87GB 160630.8+495728
ATel #16556; Federica Giacchino (INFN Roma2 & ASI SSDC, Italy), Isabella Mereu (INFN Perugia), C. C. Cheung (NRL) on behalf of the Fermi Large Area Telescope Collaboration
on 23 Mar 2024; 15:38 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 for the first time a gamma-ray flaring activity from a source positionally consistent with flat spectrum radio source 87GB 160630.8+495728, also known as NVSS J160756+494838 or 4FGL J1608.0+4949 in the fourth Fermi catalog (The Fermi-LAT collaboration 2020, ApJS, 247, 33) with VLBI radio coordinates (J2000.0), R.A = 241.98600 deg, Decl. = 49.81089 deg (Petrov et al. 2019, MNRAS, 482, 3023). The radio source is a likely blazar with an unknown redshift.
Preliminary analysis indicates that on 2024 March 21, 87GB 160630.8+495728 was in a never-before detected high flux state with a daily average gamma-ray flux (E>100MeV) of (0.15 +/- 0.07) x 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 75 times greater than the average flux reported in the 4FGL catalog. The corresponding photon index is 2.1 +/- 0.3 and is consistent with the 4FGL value of 2.27+/-0.15 within the uncertainties.
Because Fermi normally 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 strongly encourage multiwavelength observations. The gamma-ray light curve of 87GB 160630.8+495728 may be found in the Fermi LAT Light Curve Repository at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1608.0+4949. 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.
