1,100 research outputs found
Efficient charged particle propagation methods
In astrophysics, the search for sources of the highest-energy cosmic rays
continues. For further progress, not only ever better observatories but also
ever more realistic numerical simulations are needed. We compare different
approaches for numerical test simulations of UHECRs in the IGMF and show that
all methods provide correct statistical propagation characteristics of the
particles in means of their diffusive behaviour. Through convergence tests, we
show that the necessary requirements for the methods differ and ultimately
reveal significant differences in the required simulation time.Comment: Submitted to the Proceedings of the 20th International Workshop on
Advanced Computing and Analysis Techniques in Physics Research (ACAT 2021
Recurrent Neutrino Emission from Supermassive Black Hole Mergers
The recent detection of possible neutrino emission from the blazar TXS
0506+056 was the first high-energy neutrino associated with an astrophysical
source, making this special type of active galaxies promising neutrino
emitters. The fact that two distinct episodes of neutrino emission were
detected with a separation of around 3 years suggests that emission could be
periodic. Periodic emission is expected from supermassive binary black hole
systems due to jet precession close to the binary's merger. Here we show that
if TXS 0506+056 is a binary source then the next neutrino flare could occur
before the end of 2021. We derive the binary properties that would lead to the
detection of gravitational waves from this system by LISA. Our results for the
first time quantify the time scale of these correlations for the example of TXS
0506+056, providing clear predictions for both the neutrino and
gravitational-wave signatures of such sources.Comment: 6 pages, 3 figures, submitte
On the possible jet contribution to the -ray luminosity in NGC 1068
NGC 1068 is a nearby widely studied Seyfert II galaxy presenting radio,
infrared, X- and -ray emission as well as strong evidence for
high-energy neutrino emission. Recently, the evidence for neutrino emission
could be explained in a multimessenger model in which the neutrinos originate
from the corona of the active galactic nucleus (AGN). In this environment
-rays are strongly absorbed, so that an additional contribution from
e.g. the circumnuclear starburst ring is necessary. In this work, we discuss
whether the radio jet can be an alternative source of the -rays between
about and GeV as observed by Fermi-LAT. In particular, we include
both leptonic and hadronic processes, i.e. accounting for inverse Compton
emission and signatures from as well as interactions. In order
to constrain our calculations, we use VLBA and ALMA observations of the radio
knot structures, which are spatially resolved at different distances from the
supermassive black hole. Our results show that the best leptonic scenario for
the prediction of the Fermi-LAT data is provided by the radio knot closest to
the central engine. For that a magnetic field strength is
needed as well as a strong spectral softening of the relativistic electron
distribution at . However, we show that neither such a weak
magnetic field strength nor such a strong softening is expected for that knot.
A possible explanation for the 10 GeV -rays can be provided by
hadronic pion production in case of a gas density . Nonetheless, this process cannot contribute
significantly to the low energy end of the Fermi-LAT range. We conclude that
the emission sites in the jet are not able to explain the -rays in the
whole Fermi-LAT energy band
Regimes of cosmic-ray diffusion in Galactic turbulence
Cosmic-ray transport in astrophysical environments is often dominated by the diffusion of particles in a magnetic field composed of both a turbulent and a mean component. This process, which is two-fold turbulent mixing in that the particle motion is stochastic with respect to the field lines, needs to be understood in order to properly model cosmic-ray signatures. One of the most important aspects in the modeling of cosmic-ray diffusion is that fully resonant scattering, the most effective such process, is only possible if the wave spectrum covers the entire range of propagation angles. By taking the wave spectrum boundaries into account, we quantify cosmic-ray diffusion parallel and perpendicular to the guide field direction at turbulence levels above 5% of the total magnetic field. We apply our results of the parallel and perpendicular diffusion coefficient to the Milky Way. We show that simple purely diffusive transport is in conflict with observations of the inner Galaxy, but that just by taking a Galactic wind into account, data can be matched in the central 5 kpc zone. Further comparison shows that the outer Galaxy at > 5 kpc, on the other hand, should be dominated by perpendicular diffusion, likely changing to parallel diffusion at the outermost radii of the Milky Way.</p
Neurino Cadence of TXS~0506+056 Consistent with Supermassive Binary Origin
On September 18, 2022, an alert by ceCube indicated that a ~170TeV neutrino
arrived in directional coincidence with the blazar TXS 0506+056. This event
adds to two previous ones: a neutrino alert from its direction on September 22,
2017, and a 3sigma signature of a dozen neutrinos in 2014/2015. deBruijn 2020
showed that these two previous neutrino emission episodes could be due to a
supermassive binary black hole (SMBBH) where jet precession close to final
coalescence results in periodic emission. This model predicted a new emission
episode consistent with the September 18, 2022 neutrino observation. Here, we
show that the neutrino cadence of TXS 0506+056 is consistent with a SMBBH
origin with mass ratios q3e8Msun. For the
first time, we calculate the characteristic strain of the gravitational wave
emission of the binary, and show that the merger could be detectable by LISA
for black hole masses <5e8Msun if the mass ratios are in the range 0.1<q<0.3.
We predict that there can be a neutrino flare existing in the still to be
analyzed IceCube data peaking some time between 08/2019 and 01/2021 if a
precessing jet is responsible for all three detected emission episodes. The
next flare is expected to peak in the period 01/2023 to 08/2026. Further
observation will make it possible to constrain the mass ratio as a function of
the black hole mass more precisely and would open the window toward the
preparation of the detection of SMBBH mergers.Comment: 10 pages, 2 figures, submitte
Development of a general analysis and unfolding scheme and its application to measure the energy spectrum of atmospheric neutrinos with IceCube
We present the development and application of a generic analysis scheme for the measurement of neutrino spectra with the IceCube detector. This scheme is based on regularized unfolding, preceded by an event selection which uses a Minimum Redundancy Maximum Relevance algorithm to select the relevant variables and a random forest for the classification of events. The analysis has been developed using IceCube data from the 59-string configuration of the detector. 27,771 neutrino candidates were detected in 346 days of livetime. A rejection of 99.9999 % of the atmospheric muon background is achieved. The energy spectrum of the atmospheric neutrino flux is obtained using the TRUEE unfolding program. The unfolded spectrum of atmospheric muon neutrinos covers an energy range from 100 GeV to 1 PeV. Compared to the previous measurement using the detector in the 40-string configuration, the analysis presented here, extends the upper end of the atmospheric neutrino spectrum by more than a factor of two, reaching an energy region that has not been previously accessed by spectral measurements.M.G. Aartsen … G.C. Hill … S. Robertson … B. Whelan … et al. (IceCube Collaboration
Neutrino oscillation studies with IceCube-DeepCore
Abstract not availableM.G. Aartsen ... G.C. Hill ... S. Robertson ... A. Wallace ... B.J. Whelan ... et al. [IceCube Collaboration
A Search for Coincident Neutrino Emission from Fast Radio Bursts with Seven Years of IceCube Cascade Events
This paper presents the results of a search for neutrinos that are spatially and temporally coincident with 22 unique, nonrepeating fast radio bursts (FRBs) and one repeating FRB (FRB 121102). FRBs are a rapidly growing class of Galactic and extragalactic astrophysical objects that are considered a potential source of high-energy neutrinos. The IceCube Neutrino Observatory\u27s previous FRB analyses have solely used track events. This search utilizes seven years of IceCube cascade events which are statistically independent of track events. This event selection allows probing of a longer range of extended timescales due to the low background rate. No statistically significant clustering of neutrinos was observed. Upper limits are set on the time-integrated neutrino flux emitted by FRBs for a range of extended time windows
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