Fermi-LAT detection of a new gamma-ray source associated with the FSRQ S3 2152+22
ATel #14279; R. Angioni (SSDC/INFN), C. C. Cheung (NRL), I. Mereu (INFN Perugia) and D. Kocevski (MSFC/NASA) on behalf of the Fermi Large Area Telescope Collaboration
on 18 Dec 2020; 17:33 UT
Credential Certification: Roberto Angioni (r.angioni90@gmail.com)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed gamma-ray emission from a source positionally consistent with the flat-spectrum radio quasar S3 2152+22, a.k.a. CRATES J2155+2250, with coordinates R.A. = 328.776910 deg, Decl. = 22.839523 deg (J2000; Beasley et al. 2002, ApJS, 141, 13), and redshift z=1.350 (Maslennikov et al. 2010, Ap, 53, 147), a known VLBI source. This source is not in any published LAT catalog and was not detected by AGILE or EGRET.
Preliminary analysis indicates that this source was significantly detected (>5 sigma) in a high gamma-ray state in the week 30 November - 7 December 2020, with a weekly averaged gamma-ray flux (E>100MeV) of (1.7+/-0.5) X 10^-7 photons cm^-2 s^-1 and a single power-law photon index of 2.6+/-0.3 (statistical uncertainties only). The gamma-ray source is still marginally detected (>3 sigma) in the week 7-14 December 2020. The transient was identified using a method implemented within the Fermi-LAT Collaboration known as "Fermi All-sky Variability Analysis" that searches the sky for high-energy transients on weekly time scales (Ackermann et al. 2013, ApJ, 771, 57).
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Roberto Angioni (roberto.angioni@ssdc.asi.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.
