Fermi-LAT detection of renewed gamma-ray activity from the FSRQ TXS 0025+197
ATel #13860; Isabella Mereu (INFN Perugia) on behalf of the Fermi Large Area Telescope Collaboration
on 10 Jul 2020; 21:35 UT
Credential Certification: Isabella Mereu (mereuisabella@gmail.com)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar
Referred to by ATel #: 13910
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: 7.12424 deg, Dec.: 20.00742 deg (J2000, Beasley et al. 2002 ApJS, 141, 13). TXS 0025+197, also known as 4FGL J0028.4+2001, has a redshift of 1.5517+/-0.0004 (Alam et al. 2015, ApJS, 219, 12).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on July 9, 2020, with the emission of two E > 10 GeV photons (E = 11.8 GeV; time : 2020-07-09 04:12:56.731; E = 13.6 GeV; time : 2020-07-09 18:36:53.725, with association probability > 99%) and with a daily averaged gamma-ray flux (E>100MeV) of (1.0 +/- 0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). The latter corresponds to a flux increase of a factor of 80 relative to the average flux reported in the fourth Fermi-LAT catalog (4FGL, Abdollahi et al. 2020). The corresponding photon index is 1.87 +/- 0.11, and significantly smaller than the 4FGL value of 2.44 +/- 0.07. The peak 6-hour integrated gamma-ray flux (E>100 MeV) of (1.5+/-0.4) X 10^-6 photons cm^-2 s^-1 was reached by TXS 0025+197 in the interval 06:00-12:00 UT, with corresponding photon spectral index of 1.83+/-0.18. Previous bright gamma-ray activity from this object was reported in August 2019 (ATel #13032) and October 2018 (ATel #12084) . This source is one of the "LAT Monitored Sources"(https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/TXS_0025p197).
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@gmail.com) and R. Angioni (r.angioni90@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.
