Fermi-LAT detection of a new gamma-ray transient, Fermi J0207.4+6720
ATel #17732; P. Monti-Guarnieri (University of Trieste and INFN Trieste), C. C. Cheung (NRL), and P. Benke (GFZ, MPIfR), on behalf of the Fermi Large Area Telescope Collaboration
on 30 Mar 2026; 16:13 UT
Credential Certification: Giovanni La Mura (giovanni.lamura@inaf.it)
Subjects: Gamma Ray, >GeV, Transient
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 with coordinates R.A. = 31.85 deg, Dec. = +67.34 deg (J2000) and 95% error radius 0.05 deg, located close to the Galactic plane (l, b = 130.17 deg, 5.56 deg). This source is not in any published LAT catalog and was not detected by AGILE or EGRET. The error circle includes the radio source GB6 J0207+6719, with coordinates R.A. = 31.78459 deg, Dec. = +67.32104 deg (Mainzer et al. 2011, ApJ, 731, 53) and unknown redshift.
Preliminary analysis indicates that this source was significantly detected (>5 sigma) between February 1, 2026 and March 26, 2026, with an averaged gamma-ray flux (E>100MeV) of (0.11+/-0.02) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only) and a single power-law photon index of 2.15+/-0.08. The greatest daily-averaged flux of this source (E>100MeV) was (0.5+/-0.2) X 10^-6 photons cm^-2 s^-1, on March 23, 2026. The transient was initially identified through the "Fermi All-sky Variability Analysis" (https://fermi.gsfc.nasa.gov/ssc/data/access/lat/FAVA/SourceReport.php?week=916&flare=33) that searches the sky for high-energy transients on weekly time scales (Ackermann et al. 2013, ApJ, 771, 57).
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 P. 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.
