TITLE: GCN CIRCULAR NUMBER: 45002 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-260610A DATE: 26/06/19 14:05:43 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo@gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC260610A neutrino event (GCN 44899) 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 26-06-10 at 20:02:41.03 UTC (T0) with J2000 position RA = 309.20 (+2.04, -2.06) deg, Decl. = 37.22 (+0.96/-0.93) deg 90% PSF containment. Two cataloged >100 MeV gamma-ray source are located within the 90% IC260610A localization error, at a distance of roughly 0.77 and 1.45 deg (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). These are the objects: 4FGL J2035.0+3632 associated with PSR J2034+3632. Based on a preliminary analysis of the LAT data over the timescale of 1-day and 1-month, this object is not significantly detected at gamma-rays. 4FGL J2030.0+3641 associated with PSR J2030+3641. Based on a preliminary analysis of the LAT data over the timescale of 1-day, this object is not significantly detected at gamma-rays. On a 1-month integration timescale prior to T0, it is detected significantly but the flux is in agreement with the average flux of the source reported in 4FGL-DR4. We conclude that the source is not in high state. 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 IC260610A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC260610A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 2.7e-9 ph cm^-2 s^-1 for ~18-years (2008-08-04 / T0), <1.2e-08 (<2.6e-07) 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 Leonard Pfeiffer (leonard.pfeiffer at uni-wuerzburg.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. View this GCN Circular online at https://gcn.nasa.gov/circulars/45002. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...