Fermi LAT detection of a GeV gamma-ray flare from FSRQ B2 1015+35B (OL 326)
ATel #16812; Fausto Casaburo (INFN Roma Tor Vergata & SSDC ASI), Stefano Ciprini (INFN Roma Tor Vergata & SSDC ASI), Federica Giacchino (INFN Roma Tor Vergata & SSDC ASI) and Dario Gasparrini (INFN Roma Tor Vergata & SSDC ASI), on behalf of the Fermi Large Area Telescope Collaboration.
on 12 Sep 2024; 10:47 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@ssdc.asi.it)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
Referred to by ATel #: 16814
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 (FSRQ) B2 1015+35B, also known as OL 326, S4 1015+35, and 4FGL J1018.4+3540 in the 14-year fourth Fermi-LAT catalog Data Release 4 (4FGL-DR4; Ballet et al. 2024, arXiv:2307.12546), with celestial coordinates (J2000) R.A.=154.54578 deg, Dec=35.71096 deg (Truebenbach & Darling 2017, ApJS, 233, 3) and redshift z=1.23 (SSDS, Data Release 13).
Preliminary analysis indicates that B2 1015+35B was in an elevated gamma-ray emission state on September 3 and 4, 2024, reaching daily averaged gamma-ray flux (E>100MeV) of (0.9+/-0.2) x 10^-6 photons cm^-2 s^-1 (statistical uncertainties only) on both days. This value is approximately 70 times higher than the 4FGL-DR4 flux of 1.28 x 10^-8 photons cm^-2 s^-1. The corresponding photon spectral index is 2.3+/-0.2 for both days. This value is marginally consistent with the 4FGL value of the 4FGL-DR4 value of 2.54+/-0.05. This is the first time that the Fermi-LAT collaboration has reported enhanced gamma-ray activity from the blazar B2 1015+35B.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of B2 1015+35B will continue. We encourage multifrequency observations of this gamma-ray blazar. For this source, the Fermi-LAT contact people are Fausto Casaburo (fausto.casaburo[at]roma2.infn.it), and Federica Giacchino (federica.giacchino[at]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.
