Fermi-LAT detection of a new gamma-ray source Fermi J0346.0+5405, likely associated with a radio-loud AGN

ATel #17679; S. Rani (Michigan Technological University), T. Lewis (Michigan Technological University), C. C. Teddy Cheung (NRL), S. Buson (DESY Berlin, University of Würzburg), on behalf of the Fermi Large Area Telescope Collaboration
on 12 Feb 2026; 19:08 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 detected gamma-ray emission from a previously unreported low-latitude source, designated Fermi J0346.0+5405, with best-fit coordinates R.A. = 56.52 deg, Dec. = 54.09 deg (J2000), and a 95% confidence error radius of 0.14 deg.

Preliminary analysis indicates that this source was significantly detected on February 10, 2026, with a daily averaged gamma-ray flux (E > 100 MeV) of (2.5 +/- 1.2) e-7 photons cm^-2 s^-1 (statistical uncertainty only). The corresponding photon index of 1.7 +/- 0.2 indicates a hard spectrum, and the signal is present in three energy bins, including a 16 GeV photon associated with the source with high probability (p = 0.99). The detection significance for this interval is TS = 33.

A search for counterparts within the LAT localization region reveals two compact radio sources, including GB6 B0342+5351, whose broad-band SED is consistent with a blazar, and the VLBI source ICRF J034634.5+540059, both lying inside the 95% positional uncertainty circle of the LAT detection. No plausible Galactic counterpart is found. The positional correspondence suggests that Fermi J0346.0+5405 is a new gamma-ray source, likely associated with a radio-loud AGN.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. Multiwavelength observations during the ongoing activity of this source are strongly encouraged. The Fermi LAT contact person is C. C. Teddy Cheung (chi.c.cheung2.civ@us.navy.mil).

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.