Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ GB6 J0742+5444
ATel #17512; P. Monti-Guarnieri (University of Trieste and INFN Trieste), on behalf of the Fermi Large Area Telescope Collaboration
on 30 Nov 2025; 21:03 UT
Credential Certification: Chiara Bartolini (chiara.bartolini-1@unitn.it)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar
Referred to by ATel #: 17628
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar GB6 J0742+5444, also known as 87GB 073840.5+545138, BZU J0742+5444 and 4FGL J0742.6+5443 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), with coordinates R.A. = 115.66580 deg, Dec. = 54.74018 deg (J2000, Xu et al. 2019, ApJS, 242, 1), and redshift 0.723 (Halpern et al. 2003, AJ, 125, 572).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on November 29, 2025, with a daily averaged gamma-ray flux (E>100MeV) of (0.9 +/- 0.2) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 30 relative to the average flux reported in the fourth release of the fourth Fermi-LAT catalog (4FGL-DR4, Ballet, J. et al. 2023, arXiv:2307.12546). The corresponding photon index is 2.0 +/- 0.1, indicating a significantly harder spectrum than the 4FGL-DR4 value of 2.34 +/- 0.02. The Fermi-LAT Collaboration has previously reported flaring activity from this source in ATels #3445 and #3196.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for GB6 J0742+5444 can be accessed via the Fermi-LAT Light-Curve Repository at 4FGL J0742.6+5443. A preliminary estimation of the daily gamma-ray flux observed by Fermi-LAT is also publicly available on the LAT Monitored Source list at BZU_J0742p5444. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Pietro Monti-Guarnieri (pietro.monti-guarnieri@phd.units.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.
