Fermi LAT detection of a GeV flare from the FSRQ TXS 0025+197
ATel #13032; S. Buson (Univ. of Wuerzburg / UMBC) on behalf of the Fermi-LAT Collaboration
on 15 Aug 2019; 20:22 UT
Credential Certification: Sara Buson (sara.buson@gmail.com)
Subjects: Gamma Ray, Request for Observations, AGN, Blazar
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed an increasing gamma-ray flux from a source positionally coincident with the flat spectrum radio quasar TXS 0025+197 (Douglas et al. 1996 AJ, 111, 1945), at RA: 00h 28m 29.8s, Dec. +20° 00' 27'' (J2000, Beasley et al. 2002 ApJS, 141, 13). TXS 0025+197, also known as SDSS J002829.81+200026.7, has a redshift of 1.5517+/-0.0004 (Alam et al. 2015, ApJS, 219, 12).
Preliminary analysis indicates that the source was in a high state on August 14, 2019, reaching a peak daily gamma-ray flux (E>100 MeV) of (1.0 +/- 0.2) x 10^-6 ph/cm^2/s (statistical uncertainty only). This represents an increase by a factor of about 100 over the average flux reported in the fourth Fermi-LAT catalog (4FGL J0028.4+2001, The Fermi-LAT collaboration, arXiv:1902.10045). The observed flare follows an enhanced gamma-ray state observed over the past days, and is characterized by a hard spectrum, with average photon index of 2.0 +/- 0.1, significantly harder than the 4FGL average index of 2.43 +/- 0.07. Previous bright gamma-ray activity from this object was reported in October 2018 (ATel #12084), and was accompanied by an optical high state (ATel #12082).
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. Buson (sara.buson at gmail.com) and R. Angioni (angioni at mpifr-bonn.mpg.de).
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.
