Fermi LAT detection of a GeV flare from FSRQ B2 1633+38 (4C +38.41)
ATel #12027; F. Longo (University and INFN, Trieste) on behalf of the Fermi Large Area Telescope Collaboration
on 10 Sep 2018; 19:43 UT
Credential Certification: Francesco Longo (francesco.longo@ts.infn.it)
Subjects: Gamma Ray, >GeV, Transient
The Large Area Telescope (LAT), onboard the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flux from a source positionally coincident with 4C +38.41 (RA: 16h 35m 15.493s, Dec. +38d 08m 04.50s (J2000); Johnston et al. 1995, AJ, 110, 880). This is a flat spectrum radio quasar also known as B2 1633+38, OS 356 and 3EG J1635+3813, with a redshift of 1.814 (Adelman-McCarthy et al. 2008, ApJS, 175, 297).
Preliminary analysis indicates that the source on September 9, 2018 was in a high state with a gamma-ray flux (E>100 MeV) of (2.6 +/- 0.5) x 10^-6 photons/cm^2/s (statistical uncertainty only). During September 9, 2018, the flux has increased by a factor of 9 over the average flux reported in the third Fermi-LAT catalog (3FGL J1635.2+3809, Acero et al. 2015, ApJS, 218, 23).
The source was in an active state during this day as reported by WEBT/GASP (Larionov et al. ATel #12025) and AGILE (Cardillo et al. Atel #12026). A flare from this source was reported previously by AGILE (Piano et al. Atel #12005).
The source is included in the list of publicly monitored sources: its preliminary light curve can be found here: https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/1633p382
Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. In consideration of the ongoing activity of this source we strongly encourage multiwavelength observations.
The Fermi LAT contact persons are S. Ciprini (stefano.ciprini at ssdc.asi.it) and S. Buson (sara.buson at 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.
