Fermi-LAT detection of renewed gamma-ray activity from the FSRQ GB6 J0742+5444

ATel #17628; S. Rani (Michigan Technological University), T. Lewis (Michigan Technological University), on behalf of the Fermi Large Area Telescope Collaboration
on 25 Jan 2026; 07:00 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 renewed gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar GB6 J0742+5444, also known as 4FGL 0742.6+5443 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 115.66580 deg, Dec. = 54.74018 deg (J2000, Xu et al. 2019, ApJS, 242, 1), and redshift z = 0.723 (Halpern et al. 2003, AJ, 125, 572).

Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on January 23, 2026, with a daily averaged gamma-ray flux (E>100MeV) of (1.8 +/- 0.2) e-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of more than 50 relative to the average flux reported in the fourth data release of the fourth Fermi-LAT catalog (4FGL-DR4, Ballet et al. 2023, arXiv:2307.12546). The corresponding photon index is 1.8 +/- 0.1, indicating a significantly harder spectrum than the 4FGL-DR4 value of 2.34+/- 0.02. Four high-energy photons with energies 13 GeV, 10 GeV, 19 GeV and 20 GeV are associated with the source with probabilities p > 0.99. This is the highest daily flux so far observed by the LAT from this source. The Fermi-LAT Collaboration has previously reported flaring activity from this source in ATels #17512, #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 this source 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 J0742+5444. 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.