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Fermi-LAT detection of the new gamma-ray source Fermi J1511+0550, positionally consistent with the high-energy neutrino IC191119A

ATel #13306; S. Garrappa (DESY Zeuthen) and S. Buson (Univ. Wuerzburg) on behalf of the Fermi Large Area Telescope Collaboration
on 22 Nov 2019; 09:05 UT
Credential Certification: Sara Buson (sara.buson@gmail.com)

Subjects: Gamma Ray, Neutrinos, Request for Observations, AGN, Blazar

We report an update on the analysis of the region of the high-energy IC191119A neutrino event (GCN #26258) 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 2019-11-19 01:01:29.38 UT (T0) with J2000 position RA = 230.10 (+4.76, -6.48) deg, Decl. = 3.17 (+3.36, -2.09) deg 90% PSF containment.

A preliminary analysis of the LAT data reported in GCN#26261 indicated no significant (>5sigma) new excess emission (0.1 - 800 GeV) consistent with the IC191119A best-fit position in a time interval of ~11.3-years (2008-08-04 / 2019-11-19). Performing a further investigation of the region with gamma-ray observations integrated over the full ~11.3 years a new, significant (>5sigma) excess of gamma rays is detected 3.5 deg offset from the best-fit IC191119A position and within the 90% confidence localization of the direction of the neutrino.

Assuming a power-law spectrum, the best-fit localization of this new source, Fermi J1511+0550, is (J2000) RA: 277.77, Dec: 5.84 (9.3 arcmin 99% containment, 4.7 arcmin 68% containment). The gamma-ray best-fit power-law spectral parameters are flux = (7.4 +/- 3.5)e-10 ph cm^-2 s^-1 and index = 1.84 +/- 0.14. In a preliminary analysis integrating one-day and one-month gamma-ray data prior to T0, Fermi J1511+0550 is not significantly detected in the LAT data.

The blazar candidate NVSS J151100+054916 (D'Abrusco et al. 2019, ApJ, 242, 1) is located 1.6 arcmin away from the best-fit position of Fermi J1511+0550. D'Abrusco et al. suggest a BL Lac nature for this source. We encourage multiwavelength observations of this new gamma-ray source.

Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source and of the neutrino region will continue. For this source 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.