GCN Circular 33791
Subject
Fermi-LAT gamma-ray observations of IceCube-230511A
Date
2023-05-13T11:30:15Z (a year ago)
From
Simone Garrappa at DESY <simone.garrappa@desy.de>
S. Garrappa (Ruhr-Universitaet Bochum), S. Buson (Univ. of Wuerzburg) and J. Sinapius (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the IC230511A high-energy neutrino event (GCN 33773) 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 2023-05-11 at 18:03:50.10 UT (T0) with J2000 position RA = 17.05 (+3.57, -3.40) deg, Decl. = +37.08 (+3.16, -3.69) deg (90% PSF containment). Two cataloged gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are located within the 90% IC230511A localization region. These are 4FGL J0105.1+3929, associated with the BL Lac object GB6 J0105+3928 at z = 0.44 (Shaw et al. 2013, ApJ 764 135S), and the unassociated object 4FGL J0112.0+3442. Based on a preliminary analysis of the LAT data over a month and day timescale prior T0, these objects are not significantly detected at gamma rays.
We searched for intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (> 5 sigma) new excess emission (> 100 MeV) at the IC230511A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC230511A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.2e-10 ph cm^-2 s^-1 for ~14-years (2008-08-04 to 2023-05-11 UTC), and < 1.9e-8 (< 3.0e-7) 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 ruhr-uni-bochum.de), J. Sinapius (jonas.sinapius at desy.de) and S. Buson (sara.buson 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.