TITLE:   GCN CIRCULAR
NUMBER:  33350
SUBJECT: Fermi-LAT gamma-ray observations of IceCube-230217A 
DATE:    23/02/19 13:38:53 GMT
FROM:    Sara Buson at GSFC/Fermi  <sara.buson@gmail.com>

S. Buson (Univ. of Wuerzburg), S. Garrappa (Ruhr-Universitaet Bochum) and J. Sinapius (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the IC230217A high-energy neutrino event (GCN 33337) 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 2023-02-17 at 20:49:43.4 UT (T0) with J2000 position RA = 124.54 (+1.67, -3.27) deg, Decl. = +20.74 (+2.14, -2.46) deg (90% PSF containment). Three cataloged gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are located within the 90% IC230217A localization region. These are the BL Lac object 4FGL J0816.9+2050 (a.k.a. 3FHL J0816.9+2050, 5BZB J0816+205), the blazar 4FGL J0817.1+1955 (a.k.a. CRATES J081705+1958) and the BL Lac object 4FGL J0823.3+2224 (a.k.a. OJ 233). Based on a preliminary analysis of the LAT data, these objects are not significantly detected (> 5 sigma) over the timescales of 1-day and 1-month prior to T0.

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 IC230217A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC230217A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 4.5e-10 ph cm^-2 s^-1 for ~14-years (2008-08-04 to 2023-02-17 UTC), and < 1.9e-8 (<7.8e-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.