[vsnet-grb-info 27892] Fermi-LAT Gamma-ray Observations of IceCube-210510A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29995
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-210510A
DATE:    21/05/11 21:23:18 GMT
FROM:    Simone Garrappa at DESY  <simone.garrappa at desy.de>

S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and C. C. 
Cheung (Naval Research Laboratory) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC210510A neutrino event (GCN 29976) 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 2021-05-10 at 04:50:10.73 
UT (T0) with J2000 position RA = 268.42 (+1.47, -1.60) deg, Decl. = 3.81 
(+0.68, -0.64) deg (90% PSF containment). One cataloged >100 MeV 
gamma-ray source is located within the 90% IC210510A localization 
region. This is 4FGL J1747.6+0324 (4FGL-DR2, The Fermi-LAT collaboration 
2020, ApJS, 247, 33), of unknown association. Based on a preliminary 
analysis of the LAT data over the timescales of 1-day and 1-month 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 IC210510A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC210510A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 6.3e-10 ph cm^-2 s^-1 for 
~12-years (2008-08-04 to 2021-05-10 UTC), and < 6.1e-9 (< 1.8e-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 source will continue. For these observations the 
Fermi-LAT contact persons are S. Garrappa (simone.garrappa 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.