TITLE: GCN CIRCULAR NUMBER: 34298 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-230727A DATE: 23/07/30 20:23:26 GMT FROM: Simone Garrappa at DESY simone.garrappa@desy.de

S. Garrappa (Weizmann Institute of Science), C. Bartolini (INFN Bari),  S. Buson (Uni Wuerzburg) and J. Sinapius (DESY) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the IC230727A  high-energy neutrino event (GCN 34276) 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 2023-07-27 at 16:05:39.63 UT (T0) with J2000 position RA =  33.66 (+1.16, -0.77) deg, Decl. = 7.63 (+0.70, -0.64) deg (90% PSF containment). There are no Fermi 4FGL-DR4 cataloged  gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53; Ballet et al. 2023, arXiv:2307.12546) sources in the 90% IC230727A uncertainty localization region.

We searched for intermediate (days to years) timescale emission from a new gamma-ray source. Preliminary analysis indicates no significant (> 5 sigma) new excess emission (> 100 MeV) at the IC230727A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC230727A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.2e-10 ph cm^-2 s^-1 for ~15-years (2008-08-04 to 2023-07-27 UTC), and < 4.1e-9 (< 6.0e-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 region will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa at weizmann.ac.il), C. Bartolini (chiara.bartolini at ba.infn.it), S. Buson (sara.buson at uni-wuerzburg.de) and J. Sinapius (jonas.sinapius at desy.de).

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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