Abstracts of Interest
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Abstract: 2205.15985
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Title:Near-future discovery of point sources of ultra-high-energy neutrinos
Download PDFAbstract: Upcoming neutrino telescopes may discover ultra-high-energy (UHE) cosmic neutrinos, with energies beyond 100~PeV, in the next 10--20 years. Finding their sources would expose the long-sought origin of UHE cosmic rays. We search for sources by looking for multiplets of UHE neutrinos arriving from similar directions. Our forecasts are state-of-the-art, geared at neutrino radio-detection in IceCube-Gen2. They account for detector energy and angular response, and for critical, but uncertain backgrounds. We report powerful insight. Sources at declination of $-45^\circ$ to $0^\circ$ will be easiest to discover. Discovering even one steady-state source in 10~years would disfavor most known steady-state source classes as dominant. Discovering no transient source would disfavor most known transient source classes as dominant. Our results aim to inform the design of upcoming detectors.
Abstract: 2205.15963
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Title:Investigating the correlations between IceCube high-energy neutrinos and Fermi-LAT gamma-ray observations
Download PDFAbstract: We use 10 years of publicly available IceCube data to investigate the correlations between hight-energy neutrinos and various Fermi-LAT gamma-ray samples. This work considers the following gamma-ray samples:the third Fermi-LAT catalog of high-energy sources(3FHL), >100GeV Fermi-LAT events, LAT 12-year source catalog(4FGL), the fourth catalog of activate galactic nuclei(4LAC) and subsets of these samples. For each sample, both a single-source analysis and a joint likelihood analysis are performed. We find no indication that the sources in these samples produce significant high-energy neutrinos .From the null search result, we infer that each source population can produce no more than ~0.3%-27% (at the 95% confidence level) of the IceCube's diffuse neutrino flux. Since we are using a larger(10 years) dataset of IceCube neutrinos , the constriants are improved by a factor of ~2 compared to those based on 3 years of data.
Abstract: 2205.15872
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Full Text: [ PostScript, PDF]
Title:Deep learning reconstruction of the neutrino direction and energy from in-ice radio detector data
Download PDFAbstract: Ultra-high-energy (UHE) neutrinos ($>10^{16}$ eV) can be measured cost-effectively using in-ice radio detection, which has been explored successfully in pilot arrays. A large radio detector is currently being constructed in Greenland with the potential to measure the first UHE neutrino, and an order-of-magnitude more sensitive detector is being planned with IceCube-Gen2. For such shallow radio detector stations, we present an end-to-end reconstruction of the neutrino energy and direction using deep neural networks (DNNs). The DNN determines the energy with a standard deviation of a factor of two around the true energy, which meets the science requirements of UHE neutrino detectors. For the first time, we are able to predict the neutrino direction well for all event topologies including the complicated electron neutrino charged-current ($\nu_e$-CC) interactions, a significant improvement compared to previous approaches. The obtained angular resolution follows a Gaussian distribution with $\sigma \approx 0.6^\circ (0.8^\circ)$ with extended tails that push the 68\% quantile to $4^\circ (5^\circ)$ for non-$\nu_e$-CC and $\nu_e$-CC interactions, respectively. This highlights the advantages of DNNs for modeling the complex correlations in radio detector data, thereby enabling measurement of neutrino energy and direction.
Abstract: 2206.00680
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Full Text: [ PostScript, PDF]
Title:Onset of particle acceleration during the prompt phase in gamma-ray bursts as revealed by synchrotron emission in GRB160821A
Download PDFAbstract: The physical processes of the gamma-ray emission and particle acceleration during the prompt phase in GRBs are still unsettled. In order to perform an unambiguous physical modelling of observations, a clear identification of the emission mechanism is needed. An instance of a clear identification is the synchrotron emission during the very strong flare in GRB160821A, that occurs during the prompt phase at 135 s. Here we show that the distribution of the radiating electrons in this flare is initially very narrow, but later develops a power-law tail of accelerated electrons. We thus identify for the first time the onset of particle acceleration in a GRB jet. The flare is consistent with a late energy release from the central engine causing an external-shock as it encounters a preexisting ring nebula of a progenitor Wolf-Rayet star. Relativistic forward and reverse shocks develop, leading to two distinct emission zones with similar properties. The particle acceleration only occurs in the forward shock, moving into the dense nebula matter. Here, the magnetisation also decreases below the critical value, which allows for Fermi acceleration to operate. Using this fact, we find a bulk Lorentz factor of $420 \simleq \Gamma \simleq 770$, and an emission radius of $R \sim 10^{18}$ cm, indicating a tenuous gas of the immediate circumburst surrounding. The observation of the onset of particle acceleration thus gives new and independent constraints on the properties of the flow as well as on theories of particle acceleration in collisionless astrophysical shocks.
Abstract: 2206.00042
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Full Text: [ PostScript, PDF]
Title:Gravitational scattering of spinning neutrinos by a rotating black hole with a slim magnetized accretion disk
Download PDFAbstract: We study neutrinos gravitationally scattered off a rotating supermassive black hole which is surrounded by a thin accretion disk with a realistic magnetic field. Neutrinos are supposed to be Dirac particles having a nonzero magnetic moment. Neutrinos, while being scattered, move along arbitrary trajectories not restricted by the equatorial plane. We exactly account for the influence of both gravity and magnetic field on the neutrino motion and its spin evolution. We find the measurable fluxes of outgoing neutrinos taking into account the neutrino spin precession in the external field in curved spacetime. These fluxes turn out to be significantly suppressed for some parameters of the system. Finally, we discuss the possibility to observe the predicted phenomena for core-collapsing supernova neutrinos in our Galaxy.
Abstract: 2205.15116
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Title:Eta Carinae: an evolving view of the central binary, its interacting winds and its foreground ejecta
Download PDFAbstract: FUV spectra of Eta Car, recorded across two decades with HST/STIS, document multiple changes in resonant lines caused by dissipating extinction in our line of sight. The FUV flux has increased nearly ten-fold which has led to increased ionization of the multiple shells within the Homunculus and photo-destruction of molecular hydrogen. Comparison of observed resonant line profiles with CMFGEN model profiles allows separation of wind-wind collision and shell absorptions from the primary wind, P Cygni profiles.The dissipating occulter preferentially obscured the central binary and interacting winds relative to the very extended primary wind. We are now able to monitor changes in the colliding winds with orbital phase. High velocity transient absorptions occurred across the most recent periastron passage, indicating acceleration of the primary wind by the secondary wind which leads to a downstream, high velocity bowshock that is newly generated every orbital period. There is no evidence of changes in the properties of the binary winds.
Abstract: 2205.15078
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Full Text: [ PostScript, PDF]
Title:Probing the mass composition of primary cosmic rays from the effect of the geomagnetic field on EAS muons: A simulation study
Download PDFAbstract: The distribution of the muon content of highly inclined Monte Carlo cosmic ray showers is affected by the influence of Earth's geomagnetic field. It is found that the shapes of the positive and negative muon distributions get affected/modified by the influence of the Earth's geomagnetic field. Such a correlation between the earth's geomagnetic activity and the cosmic ray (CR) air shower muons is found sensitive to the primary cosmic ray mass composition.
Abstract: 2205.15040
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Full Text: [ PostScript, PDF]
Title:Ultra wide black-hole - neutron star binaries as a possible source for gravitational waves and short gamma ray bursts
Download PDFAbstract: The third observing run of the LIGO/Virgo/KARGA collaboration reported a few neutron star - black hole (NSBH) merger events. While NSBH mergers have yet to receive extensive theoretical attention, they may have a promising electromagnetic signature in the form of short gamma - ray bursts. Here we show that NSBH dynamical mergers can naturally form from ultra - wide binaries in the field. Flyby gravitational interactions with other neighbors in the galaxy in these ultra - wide systems may result in high eccentricity that drives the binary into a merger. We show that this process can result in a merger rate at the order of $\sim 10$~Gpc$^{-3}$~yr$^{-1}$ ($\sim 5$~Gpc$^{-3}$~yr$^{-1}$) for elliptical (spiral) galaxies. This channel predicts higher merger rate with higher velocity dispersion of the host - galaxy, delay time distribution which shallower than uniform but steeper that $1/t$, higher merger rate for lower BH to NS mass ratio.
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