[vsnet-grb-info 26321] Fermi-LAT Gamma-ray Observations of IceCube-200911A and detection of a new gamma-ray source, Fermi J0330.1+3743

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28421
SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-200911A and detection of a new gamma-ray source, Fermi J0330.1+3743
DATE:    20/09/14 14:54:51 GMT
FROM:    Simone Garrappa at DESY  <simone.garrappa at desy.de>

S. Garrappa (DESY-Zeuthen) and S. Buson (Univ. of Wuerzburg) on behalf 
of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
neutrino event IC200911A (GCN 28411) 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 2020-09-11 at 14:19:46.23 
UT (T0) with J2000 position RA =51.11 (+4.42 -11.01) deg, Decl. =38.11 
(+2.35 -1.99) deg. The refined contour of the 90% PSF containment region 
is reported in GCN 28411. One cataloged >100 MeV gamma-ray source is 
located within the 90% IC200911A localization region. This is 4FGL 
J0334.3+3920 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), 
associated with the radio galaxy 4C +39.12 at known redshift z = 0.02. 
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 
IC200911A best-fit position. Assuming a power-law spectrum (photon index 
= 2.0 fixed) for a point source at the IceCube best-fit position, the 
 >100 MeV flux upper limit (95% confidence) is < 5.4e-10 ph cm^-2 s^-1 
for ~12-years (2008-08-04 / 2020-09-11 UTC), < 5.6e-9 (< 5.6e-8) ph 
cm^-2 s^-1 for a 1-month (1-day) integration time before T0.

Within the 90% confidence localization of the neutrino, ~1.2 deg offset 
from the best-fit IC200911A position, a >5 sigma excess of gamma rays, 
Fermi J0330.1+3743 was detected in an analysis of the integrated LAT 
data (> 100 MeV) between 2008-08-04 and 2020-09-11. Assuming a power-law 
spectrum, the best-fit localization is (J2000) RA: 52.51, Dec: 37.73 
(0.12 deg 99% containment, 0.06 deg 68% containment), with best-fit 
spectral parameters flux = (3 +/- 1)e-9 ph cm^-2 s^-1 and index = 2.2 
+/- 0.1. In a preliminary analysis of the LAT data over one day and one 
month prior T0, Fermi J0330.1+3743 is not significantly detected in the 
LAT data. All values include the statistical uncertainty only.

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.