Search for GeV and X-Ray Flares Associated with the IceCube Track-like Neutrinos

Abstract

Dozens of high-energy neutrinos have been detected by the IceCube neutrino telescope, but no clear association with any classes of astrophysical sources has been identified so far. Recently, Kadler et al. (2016) report that a PeV cascade-like neutrino event occurs in positional and temporal coincidence with a giant gamma-ray flare of the blazar PKS B1424-418. Since IceCube track-like events have much better angular resolution, we here search for possible shortterm gamma-ray flares that are associated with the IceCube track-like events with Fermi Large Area Telescope (LAT) observations. Among them, three track-like neutrino events occur within the field of view of Fermi-LAT at the time of the detection, so search for the prompt gamma-ray emission associated with neutrinos are possible. Assuming a point source origin and a single power law spectrum for the possible gamma-ray sources associated with neutrinos, a likelihood analysis of 0.2-100 GeV photons observed by Fermi-LAT on the timescales of ∼ 12 hours and one year are performed, and for the three special neutrinos, the analysis are also performed on the timescales of thousand of seconds before and after the neutrino detection. No significant GeV excesses over the background are found and the upper limit fluxes at 95% confidence level are obtained for different timescales. We also search for possible hard X-ray transient sources associated with the IceCube track-like neutrino events, but the search also yields null results. We discuss the implication of the non-detection of gamma-ray flares for the constraints on the neutrino source density.

The γ-Ray Emission of Star-forming Galaxies

“…The lack of anisotropy in the IceCube signal and template analyses show that most ( 86 %) of the IceCube signal is likely of extragalactic origin (Aartsen et al 2017a). Moreover, the absence of neutrino point-like sources and the non-detection of muon neutrino multiplets at > 50 TeV imply that the population responsible for the majority of the IceCube neutrinos is produced by unresolved sources with a local density of ≥ 10 −8 Mpc −3 or ≥ 10 −6 Mpc −3 for evolving and non-evolving populations respectively (Ahlers & Halzen 2014;Murase & Waxman 2016;Peng & Wang 2017). Such populations could be jetted active galactic nuclei (blazars and/or radio galaxies) and star-forming galaxies.…”

Neutrinos and Ultra-high-energy Cosmic-ray Nuclei from Blazars

“…[9] has limited the fraction of this contribution to the neutrino flux from blazars to 7-27%, after a study on the spatial correlation between the directions of the IceCube neutrinos and the positions of the sampled blazars from the Fermi 2LAC catalog [10]. Correlation studies between IceCube neutrinos and GeV and X-ray flares from point sources, including blazars, have been performed as well, but no statistically significant re-sult has been found [11], except from some hints [12][13][14]. A few significant GeV blazar flares, such as 3C279 and PKS B1424-418, have been found inconsistent to be of purely protonic origin from theoretical modelings [15,16].…”

Search for Gamma-ray Emission from Accretion Flares of Tidal Disruption Events Possibly Associated with the IceCube Neutrinos

“…The IceCube telescope has detected TeV-PeV neutrinos for the first time [1,2], which opens a unique window to explore the high-energy universe. While it is known that many of the neutrinos are of astrophysical origin, as indicated by the isotropic distribution, the nature of the incontrovertible sources is unknown despite numerous crosscorrelation analyses between the IceCube point-source data and multi-wavelength catalogues (e.g., [3][4][5][6]), as well as rapid follow-up observations utilizing the real-time alert framework [7]. Thus far, a few candidates are of special interest: PKS B1424-418, NGC 1068 and GB6 J1542+6129 [8][9][10].…”