GCN Circular 32016
Subject
Fermi-LAT Gamma-ray Observations of IceCube-220509A
Event
Date
2022-05-10T22:07:22Z (4 years ago)
From
Sara Buson at GSFC/Fermi <sara.buson@gmail.com>
S. Buson (Univ. of Wuerzburg) and S. Garrappa (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy IC220509A neutrino event (GCN 32013) 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 2022-05-09 at 18:19:04.12 UT (T0) with J2000 position RA = 334.25 (+2.01, -1.44) deg, Decl. = 5.38 (+1.63, -1.65) deg (90% PSF containment). Three cataloged gamma-ray (>100 MeV) sources are located within the 90% IC220509A localization region (4FGL-DR3; arXiv:2201.11184; The Fermi-LAT collaboration 2020, ApJS, 247, 33). These are :
4FGL J2215.4+0544, associated with the blazar of uncertain type NVSS J221513+054454 (Condon et al. 1998, AJ, 115, 1693);
4FGL J2212.8+0647, associated with the flat-spectrum radio source TXS 2210+065 (Healey et al. 2007, ApJS, 171, 61);
4FGL J2224.5+0353, associated with the high-synchrotron peaked object 1RXS J222426.5+035445 (Jackson et al. 2007, MNRAS, 376, 371).
Based on a preliminary analysis of the LAT data over the timescales of 1-day and 1-month prior to T0, these objects are not significantly detected (> 5 sigma). 4FGL J2212.8+0647 displays gamma-ray activity at the ~3 sigma level during the 1-month time interval prior to T0. This is consistent with the detection of sporadic gamma-ray activity on monthly timescales from this object, as observed in a preliminary 1-month binned LAT light curve.
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 IC220509A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC220509A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 2.4e-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 to 2022-05-09 UTC), and < 5.3e-9 (< 3.5e-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 source will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa at desy.de <http://desy.de/>) and S. Buson (sara.buson at uni-wuerzburg.de <http://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.