Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ B2 1846+32B
ATel #16894; Adithiya Dinesh (Universidad Complutense de Madrid), Giovanni La Mura (INAF - O. A. Cagliari), on behalf of the Fermi Large Area Telescope Collaboration
on 4 Nov 2024; 14:44 UT
Credential Certification: Giovanni La Mura (glamura@lip.pt)
Subjects: Gamma Ray, AGN, Blazar, Quasar
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 B2 1846+32B, also known as 4FGL J1848.5+3243 (Ballet et al. 2024, arXiv:2307.12546), with coordinates R.A. = 282.14317 deg, Dec. = +32.73337 deg (J2000; Beasley et al. 2002, ApJS, 141, 13), and redshift z=0.981 (Massaro et al. 2015, ApJS, 217, 2).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on November 2, 2024, with a daily averaged gamma-ray flux (E>100MeV) of (0.5+/-0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 15 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL). The corresponding photon index is 2.11+/-0.22, indicating a significantly harder spectrum than the 4FGL value of 2.49+/-0.03. Previous gamma-ray activity of this source, detected with Fermi-LAT has been reported in ATel #8315.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for B2 1846+32B can be accessed via the Fermi-LAT Light-Curve Repository at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1848.5+3243. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Roopesh Ojha (Roopesh.Ojha@gmail.com)
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.
