Constraints on Populations of Neutrino Sources from Searches in the Directions of IceCube Neutrino Alerts

Abstract

Beginning in 2016, the IceCube Neutrino Observatory has sent out alerts in real time containing the information of high-energy (E ≳ 100 TeV) neutrino candidate events with moderate to high (≳30%) probability of astrophysical origin. In this work, we use a recent catalog of such alert events, which, in addition to events announced in real time, includes events that were identified retroactively and covers the time period of 2011–2020. We also search for additional, lower-energy neutrinos from the arrival directions of these IceCube alerts. We show how performing such an analysis can constrain the contribution of rare populations of cosmic neutrino sources to the diffuse astrophysical neutrino flux. After searching for neutrino emission coincident with these alert events on various timescales, we find no significant evidence of either minute-scale or day-scale transient neutrino emission or of steady neutrino emission in the direction of these alert events. This study also shows how numerous a population of neutrino sources has to be to account for the complete astrophysical neutrino flux. Assuming that sources have the same luminosity, an E −2.5 neutrino spectrum, and number densities that follow star formation rates, the population of sources has to be more numerous than 7 × 10−9 Mpc−3. This number changes to 3 × 10−7 Mpc−3 if number densities instead have no cosmic evolution.

Search for Continuous and Transient Neutrino Emission Associated with IceCube’s Highest-energy Tracks: An 11 yr Analysis

“…In these cases, different source populations or states produce different neutrino spectra compared to one continuous power law. Another possible scenario including a source population emitting single power laws is described in Abbasi et al (2023b). Our result agrees with the high-density scenario presented in Section 6 of Abbasi et al (2023b).…”

“…Another possible scenario including a source population emitting single power laws is described in Abbasi et al (2023b). Our result agrees with the high-density scenario presented in Section 6 of Abbasi et al (2023b). There, a highdensity source population with low individual fluxes (with an E −2.5 energy spectrum) is the origin of alert events.…”

“…In such a scenario, atmospheric background noise would dominate the lower-energy range, while the higherenergy range would yield single high-energy events. It could also be caused by a high-density source population as investigated in Abbasi et al (2023b), where high-energy events are the result of fluctuations from a large population of sources with individually weak fluxes. In this case, the lower-energy flux would still be too low to be detected.…”

On the “Loose” Constraint from IceCube Neutrino Nondetection of GRB 230307A

“…Note that the neutrino emission could occur during the prompt phase of GRB as well as the (choked) jetʼs propagation within the macronova/kilonova ejecta or a massive progenitor envelope (e.g., Mészáros & Waxman 2001;Murase & Ioka 2013;Senno et al 2016;Kimura et al 2018), as a precursor for GRBs. However, until now, no evident correlation between neutrino events and observed GRBs has been observed (e.g., Aartsen et al 2017;Abbasi et al 2023a).…”

Searches for Neutrinos in the Direction of Radio-bright Blazars with the ANTARES Telescope

“…However, their origins are still not fully determined. Observational evidence exists for a wide range of neutrino sources, including individual active galaxies (Aartsen et al 2018a(Aartsen et al , 2018bAbbasi et al 2022a), large samples of blazars (Giommi et al 2020;Plavin et al 2020Plavin et al , 2021Plavin et al , 2023Buson et al 2022Buson et al , 2023Kun et al 2022;Abbasi et al 2023a), and the Milky Way (Albert et al 2017a(Albert et al , 2018a(Albert et al , 2023Neronov & Semikoz 2016;Aartsen et al 2019;Kovalev et al 2022;Abbasi et al 2023b).…”