Fermi-LAT detection of a new gamma-ray source, Fermi J1443+7152

ATel #17773; C. C. Cheung (NRL), J. Valverde (Marquette University), on behalf of the Fermi Large Area Telescope Collaboration
on 5 May 2026; 00:50 UT
Credential Certification: Teddy Cheung (Teddy.Cheung@nrl.navy.mil)

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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 with coordinates R.A. = 220.89 deg., Dec. = +71.87 deg. (J2000) and 95% error radius 0.10 deg. This source is not in any published LAT catalog and was not detected by AGILE or EGRET. The gamma-ray source has no obvious counterpart at other wavelengths, although we note an optical transient consistent with the LAT localization, AT 2026jcu (MASTER OT J144431.58+715525.9) was detected on April 9, 2026 (https://www.wis-tns.org/object/2026jcu).

Preliminary analysis indicates that this source was first significantly detected (>5 sigma) between April 20-27, 2026, with a 1-week averaged gamma-ray flux (E>100MeV) of (1.4+/-0.3) X 10^-7 photons cm^-2 s^-1 (statistical uncertainty only) and a single power-law photon index of 2.2+/-0.2. The source was identified through the "Fermi All-sky Variability Analysis" (FAVA; https://fermi.gsfc.nasa.gov/ssc/data/access/lat/FAVA/SourceReport.php?week=925&flare=9) that searches the sky for high-energy transients on weekly time scales (Ackermann et al. 2013, ApJ, 771, 57). Inspection of the FAVA database indicates the source was present at lower significances for several 1-week intervals beginning on March 9, 2026. Summing eight weeks of data from March 9.0 - May 4.0, 2026, gives a best-fit localization quoted above, with an averaged gamma-ray flux (E>100MeV) of (5.9+/-0.8) X 10^-8 photons cm^-2 s^-1 (statistical uncertainty only) and a single power-law photon index of 2.3+/-0.1.

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 C.C. Cheung (Teddy.Cheung@nrl.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.