Fermi-LAT detection of a new gamma-ray source associated with the FSRQ TXS 1041+536

ATel #17293; C. Bartolini (University of Trento & INFN Bari), G. La Mura (INAF - Astronomical Observatory of Cagliari), on behalf of the Fermi Large Area Telescope Collaboration
on 19 Jul 2025; 20:36 UT
Credential Certification: Giovanni La Mura (giovanni.lamura@inaf.it)

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The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed gamma-ray emission from a source positionally consistent with the flat-spectrum radio quasar TXS 1041+536, with coordinates R.A. = 161.04447 deg, Dec. = +53.37237 deg (J2000; Xu et al. 2019, ApJS, 242, 5), and redshift z = 1.903 (Albareti et al. 2017, ApJS, 233, 25). This source is not in any published LAT catalog and was not detected by AGILE or EGRET.

Preliminary analysis indicates that this source was significantly detected (>5 sigma) in a high gamma-ray state on July 18, 2025, with a daily averaged gamma-ray flux (E>100MeV) of (0.6+/-0.1) X 10^-6 photons cm^-2 s^-1 and a single power-law photon index of 2.1+/-0.2 (statistical uncertainties only).

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Chiara Bartolini (Chiara.Bartolini@ba.infn.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.