139 research outputs found
Search for High-Energy Neutrinos from TDE-like Flares with IceCube
The collected data of IceCube, a cubic kilometre neutrino detector array in
the Antarctic ice, reveal a diffuse flux of astrophysical neutrinos. The
extragalactic sources of the majority of these neutrinos however have yet to be
discovered. Tidal Disruption Events (TDEs), disruption outbursts from black
holes that accrete at an enhanced rate, are candidates for being the sources of
extragalactic, high-energy neutrinos. Stein et al. (2021) and Reusch et al.
(2022) have reported the coincidence of two likely TDEs from supermassive black
holes and public IceCube neutrino events (alerts). Further work by van Velzen
et al. (2021) identified a third event in coincidence with a high-energy
neutrino alert and a correlation between a broader set of similar
TDE-like flares and IceCube alerts. We conducted a stacking analysis with a
29-flare subset of the TDE-like flares tested by van Velzen et al. This work
was done with neutrinos with energies above GeV. The
resulting p-value of 0.45 is consistent with background. In this contribution,
I will discuss the results of the stacking analysis, as well as the impact of
using different reconstruction algorithms on the three correlated realtime
alerts.Comment: Presented at the 38th International Cosmic Ray Conference (ICRC2023).
See arXiv:2307.13047 for all IceCube contribution
ASAS-SN follow-up of IceCube high-energy neutrino alerts
We report on the search for optical counterparts to IceCube neutrino alerts
released between April 2016 and August 2021 with the All-Sky Automated Survey
for SuperNovae (ASAS-SN). Despite the discovery of a diffuse astrophysical
high-energy neutrino flux in 2013, the source of those neutrinos remains
largely unknown. Since 2016, IceCube has published likely-astrophysical
neutrinos as public realtime alerts. Through a combination of normal survey and
triggered target-of-opportunity observations, ASAS-SN obtained images within 1
hour of the neutrino detection for 20% (11) of all observable IceCube alerts
and within one day for another 57% (32). For all observable alerts, we obtained
images within at least two weeks from the neutrino alert. ASAS-SN provides the
only optical follow-up for about 17% of IceCube's neutrino alerts. We recover
the two previously claimed counterparts to neutrino alerts, the flaring-blazar
TXS 0506+056 and the tidal disruption event AT2019dsg. We investigate the light
curves of previously-detected transients in the alert footprints, but do not
identify any further candidate neutrino sources. We also analysed the optical
light curves of Fermi 4FGL sources coincident with high-energy neutrino alerts,
but do not identify any contemporaneous flaring activity. Finally, we derive
constraints on the luminosity functions of neutrino sources for a range of
assumed evolution models
Neutrino follow-up with the Zwicky Transient Facility: Results from the first 24 campaigns
The Zwicky Transient Transient Facility (ZTF) performs a systematic neutrino
follow-up program, searching for optical counterparts to high-energy neutrinos
with dedicated Target-of-Opportunity (ToO) observations. Since first light in
March 2018, ZTF has taken prompt observations for 24 high-quality neutrino
alerts from the IceCube Neutrino Observatory, with a median latency of 12.2
hours from initial neutrino detection. From two of these campaigns, we have
already reported tidal disruption event (TDE) AT2019dsg and likely TDE
AT2019fdr as probable counterparts, suggesting that TDEs contribute >7.8% of
the astrophysical neutrino flux. We here present the full results of our
program through to December 2021. No additional candidate neutrino sources were
identified by our program, allowing us to place the first constraints on the
underlying optical luminosity function of astrophysical neutrino sources.
Transients with optical absolutes magnitudes brighter that -21 can contribute
no more than 87% of the total, while transients brighter than -22 can
contribute no more than 58% of the total, neglecting the effect of extinction.
These are the the first observational constraints on the neutrino emission of
bright populations such as superluminous supernovae. None of the neutrinos were
coincident with bright optical AGN flares comparable to that observed for TXS
0506+056/IC170922A, suggesting that most astrophysical neutrinos are not
produced during such optical flares. We highlight the outlook for
electromagnetic neutrino follow-up programs, including the expected potential
for the Rubin Observatory.Comment: To be submitted to MNRAS, comments welcome
Non-standard neutrino interactions in IceCube
Non-standard neutrino interactions (NSI) may arise in various types of new physics. Their existence would change the potential that atmospheric neutrinos encounter when traversing Earth matter and hence alter their oscillation behavior. This imprint on coherent neutrino forward scattering can be probed using high-statistics neutrino experiments such as IceCube and its low-energy extension, DeepCore. Both provide extensive data samples that include all neutrino flavors, with oscillation baselines between tens of kilometers and the diameter of the Earth.
DeepCore event energies reach from a few GeV up to the order of 100 GeV - which marks the lower threshold for higher energy IceCube atmospheric samples, ranging up to 10 TeV.
In DeepCore data, the large sample size and energy range allow us to consider not only flavor-violating and flavor-nonuniversal NSI in the μ−τ sector, but also those involving electron flavor.
The effective parameterization used in our analyses is independent of the underlying model and the new physics mass scale. In this way, competitive limits on several NSI parameters have been set in the past. The 8 years of data available now result in significantly improved sensitivities. This improvement stems not only from the increase in statistics but also from substantial improvement in the treatment of systematic uncertainties, background rejection and event reconstruction
IceCube Search for Earth-traversing ultra-high energy Neutrinos
The search for ultra-high energy neutrinos is more than half a century old. While the hunt for these neutrinos has led to major leaps in neutrino physics, including the detection of astrophysical neutrinos, neutrinos at the EeV energy scale remain undetected. Proposed strategies for the future have mostly been focused on direct detection of the first neutrino interaction, or the decay shower of the resulting charged particle. Here we present an analysis that uses, for the first time, an indirect detection strategy for EeV neutrinos. We focus on tau neutrinos that have traversed Earth, and show that they reach the IceCube detector, unabsorbed, at energies greater than 100 TeV for most trajectories. This opens up the search for ultra-high energy neutrinos to the entire sky. We use ten years of IceCube data to perform an analysis that looks for secondary neutrinos in the northern sky, and highlight the promise such a strategy can have in the next generation of experiments when combined with direct detection techniques
Posteriori analysis on IceCube double pulse tau neutrino candidates
The IceCube Neutrino Observatory at the South Pole detects Cherenkov light emitted by charged secondary particles created by primary neutrino interactions. Double pulse waveforms can arise from charged current interactions of astrophysical tau neutrinos with nucleons in the ice and the subsequent decay of tau leptons. The previous 8-year tau double pulse analysis found three tau neutrino candidate events. Among them, the most promising one observed in 2014 is located very near the dust layer in the middle of the detector. A posterior analysis on this event will be presented in this paper, using a new ice model treatment with continuously varying nuisance parameters to do the targeted Monte Carlo re-simulation for tau and other background neutrino ensembles. The impact of different ice models on the expected signal and background statistics will also be discussed
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