Tau neutrinos are unique cosmic messengers, especially at extreme energies. When they undergo a charged-current interaction, the short lifetime of the produced tau gives rise to secondary tau ...neutrinos that carry a significant fraction of the primary neutrino energy. Here we apply this effect, known as tau neutrino regeneration, to extremely high energy neutrinos passing through Earth. We find that for most column depths, with the exception of propagation through the core, Earth-traversing tau neutrinos emerge at (PeV) energies. We use these secondaries to estimate the expected signal from cosmogenic fluxes at IceCube and find a non-negligible contribution to the astrophysical component above 1 PeV . We also constrain the anomalous ANITA observations via the accompanying secondaries expected at IceCube. We calculate that ANITA should see fewer than 10−7 events in the reported direction, regardless of assumed source energy spectrum, ruling out the possibility that these events are astrophysical in origin under Standard Model assumptions.
The discovery of high-energy astrophysical neutrinos by IceCube in 2013 and of gravitational waves by LIGO in 2015 have enabled a new era of multi-messenger astronomy. Gravitational waves (GWs) can ...identify the merging of compact objects such as neutron stars and black holes. These compact mergers, especially neutron star mergers, are potential neutrino sources. Identifying joint sources of GWs and neutrinos would be a major breakthrough in multi-messenger astrophysics and allow us to understand the dynamics of compact binary mergers as well as understand the particle acceleration mechanisms taking place in these extreme environments.In this thesis we study the correlation between compact binary mergers and high-energy neutrino emission. We use IceCube neutrino data together with GW data provided by the LIGO Virgo Collaboration (LVC) to search for neutrino counterparts to GW events observed by LVC. We perform an unbinned maximum likelihood analysis which uses uses a neutrino likelihood along with localization information provided by LVC to search for joint sources of GWs and high-energy neutrinos.During LVC's three observing run, we followed up over 70 GW events with IceCube data. We also developed a low-latency pipeline capable of performing rapid neutrino follow up searches within minutes of a GW detection and report the results to the astronomical community. Overall we performed multiple follow up searches for both long and short time scale neutrino emission from GW events using multiple neutrino data samples. No significant neutrino emission is observed in any analysis and upper limits are placed on the time-integrated, energy scaled neutrino flux, E2F, observed at IceCube from each GW event. We also place upper limits on the total isotropic equivalent energy, Eiso, emitted in high-energy neutrinos by each GW event.While no neutrino emission is observed in the analyses described here, the methods described here demonstrate the potential for discovering joint sources of GWs and high-energy neutrinos given enough high-quality neutrino and GW data.
Realtime analyses are necessary to identify the source of high energy neutrinos. As an observatory with a 4\(\pi\) steradian field of view and near-100% duty cycle, the IceCube Neutrino Observatory ...is a unique facility for investigating transients. In 2016, IceCube established a pipeline that uses low-latency data to rapidly respond to astrophysical events that were of interest to the multi-messenger observational community. Here, we describe this pipeline and summarize the results from all of the analyses performed since 2016. We focus not only on those analyses which were performed in response to transients identified using other messengers such as photons and gravitational waves, but also on how this pipeline can be used to constrain populations of astrophysical neutrino transients by following up high-energy neutrino alerts.
The IceCube DeepCore is a dense infill array of the IceCube Neutrino Observatory at the South Pole. While IceCube is best suited for detecting neutrinos with energies of several 100 GeV and above, ...DeepCore allows to probe neutrinos with lower energies. We focus on a sample of neutrinos with energies above approximately 10 GeV, which was originally optimised for oscillation experiments. Recently, it has been adapted to enable searches for transient sources of astrophysical neutrinos in the sky. In particular, this low-energy dataset can be used to conduct follow-up searches of gravitational wave transients detected by the LIGO-Virgo instruments. A study of this, which complements IceCube's follow-up of gravitational wave events using high-energy neutrino samples, will be discussed here.
The discoveries of high-energy astrophysical neutrinos by IceCube in 2013 and of gravitational waves by LIGO in 2015 have enabled a new era of multi-messenger astronomy. Gravitational waves can ...identify the merging of compact objects such as neutron stars and black holes. These compact mergers, especially neutron star mergers, are potential neutrino sources. We present an analysis searching for neutrinos from gravitational wave sources reported by the LIGO Virgo Collaboration (LVC). We use a dedicated transient likelihood analysis combining IceCube events with source localizations provided by LVC as spatial priors. We report results for all gravitational wave events from the O1, O2, and O3 observing runs.
We summarize initial results for high-energy neutrino counterpart searches coinciding with gravitational-wave events in LIGO/Virgo's GWTC-2 catalog using IceCube's neutrino triggers. We did not find ...any statistically significant high-energy neutrino counterpart and derived upper limits on the time-integrated neutrino emission on Earth as well as the isotropic equivalent energy emitted in high-energy neutrinos for each event.
Tau neutrinos are unique cosmic messengers, especially at extreme energies. When they undergo a charged-current interaction, the short lifetime of the produced tau gives rise to secondary tau ...neutrinos that carry a significant fraction of the primary neutrino energy. This effect, known as tau neutrino regeneration, has not been applied to its full potential in current generation neutrino experiments. In this work, we present an updated calculation of tau neutrino regeneration, and explore its implications for two scenarios: the recent anomalous ANITA events and the cosmogenic neutrino flux. For the former, we investigate the idea of localized emission and find that the maximum secondary neutrino flux allowed by IceCube measurements implies a primary flux that is incompatible with the ANITA observation, regardless of the assumed source energy spectrum. For the latter, we study the prospect of detecting the cosmogenic neutrino flux of regenerated PeV neutrinos with current and next generation neutrino detectors.
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