Fermi LAT detection of a GeV gamma-ray flare from the FSRQ TXS 0358+210
ATel #13354; Stefano Ciprini (1. INFN Roma Tor Vergata; 2. ASI Space Science Data Center; Italy), on behalf of the Fermi Large Area Telescope Collaboration
on 17 Dec 2019; 11:37 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@ssdc.asi.it)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Black Hole, Blazar, Quasar
Referred to by ATel #: 16085
The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray emission from a source positionally consistent with the flat spectrum radio quasar object TXS 0358+210 (also known as MG2 J040146+2110, GB6 J0401+2110 and 4FGL J0401.7+2112, Fermi-LAT Coll. 2019arXiv190210045T) with radio coordinates (J2000) R.A.: 60.43819 deg, Dec.: 21.17461 deg (Beasley et al. 2002, ApJS 141, 13). TXS 0358+210 has a redshift z=0.834 (Sowards-Emmerd et al. 2005, ApJ 626, 95).
Preliminary analysis indicates that on 2019 December 15, TXS 0358+210 was in a high state with a daily averaged gamma-ray flux (E>100 MeV) of (0.4+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), about 25 times greater than its eight-year average flux reported in the fourth Fermi-LAT source catalog (4FGL). The corresponding photon spectral index (E>100 MeV) of 1.9+/-0.2 (statistical uncertainty only) is smaller than the 4FGL catalog value of 2.43+/-0.05.
This is the first time that the Fermi-LAT Collaboration is announcing a gamma-ray flare on daily timescale from TXS 0358+210 and it has not been reported by AGILE so far. Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of the TXS 0358+210 blazar will continue. In consideration of the ongoing activity of this source, we encourage multiwavelength observations. For this source the Fermi LAT contact person is S. Ciprini (stefano.ciprinissdc.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.
