| 1. |
- Abbasi, Rasha, et al.
(författare)
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In situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory
- 2024
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Ingår i: The Cryosphere. - : Copernicus Publications. - 1994-0416 .- 1994-0424. ; 18:1, s. 75-102
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Tidskriftsartikel (refereegranskat)abstract
- The IceCube Neutrino Observatory instruments about 1 km 3 of deep, glacial ice at the geographic South Pole. It uses 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. An unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. We examine birefringent light propagation through the polycrystalline ice microstructure as a possible explanation for this effect. The predictions of a first-principles model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties include not only the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube light-emitting diode (LED) calibration data, the theory and parameterization of the birefringence effect, the fitting procedures of these parameterizations to experimental data, and the inferred crystal properties.
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| 2. |
- Abbasi, R., et al.
(författare)
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Search for 10-1000 GeV Neutrinos from Gamma-Ray Bursts with IceCube
- 2024
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Ingår i: Astrophysical Journal. - : Institute of Physics (IOP). - 1538-4357 .- 0004-637X. ; 964:2
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of a search for 10-1000 GeV neutrinos from 2268 gamma-ray bursts (GRBs) over 8 yr of IceCube-DeepCore data. This work probes burst physics below the photosphere where electromagnetic radiation cannot escape. Neutrinos of tens of giga electronvolts are predicted in sub-photospheric collision of free-streaming neutrons with bulk-jet protons. In a first analysis, we searched for the most significant neutrino-GRB coincidence using six overlapping time windows centered on the prompt phase of each GRB. In a second analysis, we conducted a search for a group of GRBs, each individually too weak to be detectable, but potentially significant when combined. No evidence of neutrino emission is found for either analysis. The most significant neutrino coincidence is for Fermi-GBM GRB bn 140807500, with a p-value of 0.097 corrected for all trials. The binomial test used to search for a group of GRBs had a p-value of 0.65 after all trial corrections. The binomial test found a group consisting only of GRB bn 140807500 and no additional GRBs. The neutrino limits of this work complement those obtained by IceCube at tera electronvolt to peta electronvolt energies. We compare our findings for the large set of GRBs as well as GRB 221009A to the sub-photospheric neutron-proton collision model and find that GRB 221009A provides the most constraining limit on baryon loading. For a jet Lorentz factor of 300 (800), the baryon loading on GRB 221009A is lower than 3.85 (2.13) at a 90% confidence level.
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| 3. |
- Abbasi, R., et al.
(författare)
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Search for Continuous and Transient Neutrino Emission Associated with IceCube's Highest-energy Tracks: An 11 yr Analysis
- 2024
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Ingår i: Astrophysical Journal. - : Institute of Physics (IOP). - 1538-4357 .- 0004-637X. ; 964:1
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Tidskriftsartikel (refereegranskat)abstract
- IceCube alert events are neutrinos with a moderate-to-high probability of having astrophysical origin. In this study, we analyze 11 yr of IceCube data and investigate 122 alert events and a selection of high-energy tracks detected between 2009 and the end of 2021. This high-energy event selection (alert events + high-energy tracks) has an average probability of >= 0.5 of being of astrophysical origin. We search for additional continuous and transient neutrino emission within the high-energy events' error regions. We find no evidence for significant continuous neutrino emission from any of the alert event directions. The only locally significant neutrino emission is the transient emission associated with the blazar TXS 0506+056, with a local significance of 3 sigma, which confirms previous IceCube studies. When correcting for 122 test positions, the global p-value is 0.156 and compatible with the background hypothesis. We constrain the total continuous flux emitted from all 122 test positions at 100 TeV to be below 1.2 x 10-15 (TeV cm2 s)-1 at 90% confidence assuming an E -2 spectrum. This corresponds to 4.5% of IceCube's astrophysical diffuse flux. Overall, we find no indication that alert events in general are linked to lower-energetic continuous or transient neutrino emission.
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| 4. |
- Abbasi, R., et al.
(författare)
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Search for Galactic Core-collapse Supernovae in a Decade of Data Taken with the IceCube Neutrino Observatory
- 2024
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Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 1538-4357 .- 0004-637X. ; 961:1
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Tidskriftsartikel (refereegranskat)abstract
- The IceCube Neutrino Observatory has been continuously taking data to search for O(0.5–10) s long neutrino bursts since 2007. Even if a Galactic core-collapse supernova is optically obscured or collapses to a black hole instead of exploding, it will be detectable via the O(10) MeV neutrino burst emitted during the collapse. We discuss a search for such events covering the time between 2008 April 17 and 2019 December 31. Considering the average data taking and analysis uptime of 91.7% after all selection cuts, this is equivalent to 10.735 yr of continuous data taking. In order to test the most conservative neutrino production scenario, the selection cuts were optimized for a model based on an 8.8 solar mass progenitor collapsing to an O–Ne–Mg core. Conservative assumptions on the effects of neutrino oscillations in the exploding star were made. The final selection cut was set to ensure that the probability to detect such a supernova within the Milky Way exceeds 99%. No such neutrino burst was found in the data after performing a blind analysis. Hence, a 90% C.L. upper limit on the rate of core-collapse supernovae out to distances of ≈25 kpc was determined to be 0.23 yr−1. For the more distant Magellanic Clouds, only high neutrino luminosity supernovae will be detectable by IceCube, unless external information on the burst time is available. We determined a model-independent limit by parameterizing the dependence on the neutrino luminosity and the energy spectrum.
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| 5. |
- Valtonen-Mattila, Nora
(författare)
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IceCube Search of MeV Neutrino Bursts Correlated with Gravitational Waves from LIGO-Virgo-KAGRA
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Numerous models predict MeV neutrino production correlated with gravitational waves from neutron star merger systems. The IceCube Neutrino Observatory is sensitive to the MeV neutrinos from bright transients such as core-collapse supernovae via the Supernova Data Acquisition system (SNDAQ). We perform a search for MeV neutrinos correlated with gravitational waves, using the data recorded by SNDAQ and the times of the gravitational wave detections. We searched in four different search windows: 0.5 s, 1.5 s, 4 s, and 10 s. We then perform a binomial test on the two populations in the catalog: those events that contain no neutron star (Binary black hole mergers) and events that contain at least one neutron star (binary neutron star mergers and black hole - neutron star mergers).
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| 6. |
- Valtonen-Mattila, Nora
(författare)
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Searching for IceCube Neutrinos from the Death of Stars and Beyond: From MeV to PeV Energies
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The stellar death and its aftermath are compelling systems to study due to their extreme conditions and a rich array of observable messengers, such as photons, gravitational waves, and neutrinos. Neutrinos, as messengers of these systems, are particularly interesting due to their ability to traverse space unimpeded by interstellar debris, magnetic fields, or photons, thus preserving important information about the source, with different sites of production that influence the neutrino energy from nuclear processes in very dense and hot environments producing thermal MeV energy neutrinos to cosmic acceleration sites, where matter collides in shocks, producing high energy neutrinos in the O(>GeV-TeV). These neutrinos can be observed by neutrino telescopes such as the IceCube Neutrino Observatory, which has sensitivity for neutrinos from the MeV to >PeV energy ranges. In this thesis, we performed several searches, focusing on MeV neutrinos from Gamma Ray Bursts and Neutron Star Mergers, making use of information from other messengers such as photons and gravitational waves to inform our search, and >GeV neutrinos from Core-Collapse Supernovae. We produced MeV neutrino flux limits for GRB 221009A and provided detection horizon limits for >GeV neutrinos from Core-Collapse Supernovae. We also introduced a novel methodology for producing model-independent MeV neutrino flux and luminosity limits, developed a new IceCube MeV energy real-time fast analysis for the follow-up of external alerts from other observatories, and demonstrated how to search for MeV neutrinos correlated with gravitational waves.
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