GCN Circular 36230
Subject
Fermi-LAT gamma-ray observations of IceCube-240419A
Date
2024-04-22T16:20:44Z (11 days ago)
From
chiara.bartolini-1@unitn.it
Via
Web form
C. Bartolini (INFN Bari), S. Garrappa (Weizmann Institute of Science), S. Buson (DESY; Univ. of Wuerzburg), L. Pfeiffer (Univ. of Wuerzburg) and J. Sinapius (DESY) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy IC240419A neutrino event (GCN 36196) 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 2024-04-19 at 23:25:41.05 UT (T0) with J2000 position RA = 73.17 (+2.60, -3.74) deg, Decl. = +1.64 (+1.27, -1.09) deg (90% PSF containment). There is one cataloged gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) source located within the 90% IC240419A localization region. This is 4FGL J0502.6+0036, located at 2.69 degrees from the best-fit neutrino position. Based on a preliminary analysis of the LAT data over the timescales of 1-month and 1-day prior to T0, this object is not significantly detected (> 5 sigma).
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 IC240419A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC240419A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 5.98e-10 ph cm^-2 s^-1 for ~15-years (2008-08-04 to 2024-04-19 UTC), and < 1.33e-8 (< 1.24e-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 this observation 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.