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Fermi-LAT detection of a new gamma-ray source associated with the high-redshift FSRQ TXS 0552+398

ATel #11137; R. Angioni (MPIfR-Bonn), C. C. Cheung (NRL) on behalf of the Fermi-LAT collaboration
on 7 Jan 2018; 06:39 UT
Credential Certification: Sara Buson (sara.buson@gmail.com)

Subjects: Gamma Ray, AGN, Blazar

The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray emission from a source positionally consistent with the Flat-Spectrum Radio Quasar (FSRQ) TXS 0552+398, also known as B2 0552+39A, with coordinates R.A. = 88.8783567 deg, Decl. = 39.8136569 deg (J2000; Jonhston et al. 1995 AJ, 110, 880), at redshift of z=2.635 (Wills & Wills 1976 ApJS, 31, 143). This source is not in any published LAT catalog and was not detected by AGILE or EGRET.

Preliminary analysis indicates that this source went into a high-flux state on 5 January 2018, with a daily averaged gamma-ray flux (E>100MeV) of (1.3+/-0.2) X 10^-6 photons cm^-2 s^-1 and a single power-law photon index of 1.98+/-0.12 (statistical uncertainty only).

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. This source is being added to the "LAT Monitored Sources" and consequently a preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT will be publicly available (http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/). We encourage further multifrequency observations of this source. The Fermi-LAT contact person for this source is 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.