TITLE: GCN CIRCULAR NUMBER: 39048 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-250101A DATE: 25/01/27 17:49:14 GMT FROM: chiara.bartolini-1@unitn.it
C. Bartolini (Università di Trento & INFN Bari), S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and J. Sinapius (DESY) 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 IC250101A neutrino event (GCN 38770) 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 2025-01-01 21:13:17.730 UTC (T0) with J2000 position RA = 318.96 (+0.64, -0.63) deg, Decl. = -0.93 (+0.49, -0.44) deg 90% PSF containment. One cataloged >100 MeV gamma-ray source is located within the 90% IC-250101A localization error, at a distance of roughly 0.3 deg (Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). This is the object 4FGL J2115.9-0113. Based on a preliminary analysis of the LAT data over the timescale of one month prior T0, this object is 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 IC250101A 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 <2.0e-09 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <1.1e-09 ph cm^-2 s^-1 for a 1-month 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 C. Bartolini (chiara.bartolini at ba.infn.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.
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