TITLE: GCN CIRCULAR NUMBER: 39251 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-250207A DATE: 25/02/09 14:45:10 GMT FROM: Simone Garrappa at Weizmann Institute of Science <simone.garrappa@weizmann.ac.il> S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg), C. Bartolini (INFN Bari), S. Buson (DESY, Univ. of Wuerzburg) and P. M. Veres (Ruhr University Bochum) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250207A neutrino event (GCN 39203) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-02-07 02:07:55.27 UTC (T0) with J2000 position RA = 132.93 (+2.05, -1.89) deg, Decl. = 20.66 (+1.28, -1.40) deg 90% PSF containment. Two cataloged gamma-ray sources are found within the 90% IC250207A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). These are 4FGL J0854.8+2006 (associated with the FSRQ OJ 287) and 4FGL J0856.8+2056 (associated with the FSRQ TXS 0853+211) at 0.9 deg and 1.2 deg from the best-fit neutrino position, respectively. Based on a preliminary analysis of the LAT data over the timescales of 1-day and 1-month before T0, these objects are not significantly detected at gamma-rays. We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250207A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is <2.4e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <6.9e-09(<5.6e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is S. Garrappa (simone.garrappa at weizmann.ac.il). 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/39251. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...