147 research outputs found
Solitary waves in the Nonlinear Dirac Equation
In the present work, we consider the existence, stability, and dynamics of
solitary waves in the nonlinear Dirac equation. We start by introducing the
Soler model of self-interacting spinors, and discuss its localized waveforms in
one, two, and three spatial dimensions and the equations they satisfy. We
present the associated explicit solutions in one dimension and numerically
obtain their analogues in higher dimensions. The stability is subsequently
discussed from a theoretical perspective and then complemented with numerical
computations. Finally, the dynamics of the solutions is explored and compared
to its non-relativistic analogue, which is the nonlinear Schr{\"o}dinger
equation. A few special topics are also explored, including the discrete
variant of the nonlinear Dirac equation and its solitary wave properties, as
well as the PT-symmetric variant of the model
Searching for TeV Dark Matter in Irregular dwarf galaxies with HAWC Observatory
We present the results of dark matter (DM) searches in a sample of 31 dwarf
irregular (dIrr) galaxies within the field of view of the HAWC Observatory.
dIrr galaxies are DM dominated objects, which astrophysical gamma-ray emission
is estimated to be negligible with respect to the secondary gamma-ray flux
expected by annihilation or decay of Weakly Interacting Massive Particles
(WIMPs). While we do not see any statistically significant DM signal in dIrr
galaxies, we present the exclusion limits () for annihilation
cross-section and decay lifetime for WIMP candidates with masses between
and . Exclusion limits from dIrr galaxies are relevant and
complementary to benchmark dwarf Spheroidal (dSph) galaxies. In fact, dIrr
galaxies are targets kinematically different from benchmark dSph, preserving
the footprints of different evolution histories. We compare the limits from
dIrr galaxies to those from ultrafaint and classical dSph galaxies previously
observed with HAWC. We find that the contraints are comparable to the limits
from classical dSph galaxies and orders of magnitude weaker than
the ultrafaint dSph limits.Comment: 22 pages, 11 figures, 3 table
HAWC Study of Very-High-Energy -ray Spectrum of HAWC J1844-034
Recently, the region surrounding eHWC J1842-035 has been studied extensively
by gamma-ray observatories due to its extended emission reaching up to a few
hundred TeV and potential as a hadronic accelerator. In this work, we use 1,910
days of cumulative data from the High Altitude Water Cherenkov (HAWC)
observatory to carry out a dedicated systematic source search of the eHWC
J1842-035 region. During the search we have found three sources in the region,
namely, HAWC J1844-034, HAWC J1843-032, and HAWC J1846-025. We have identified
HAWC J1844-034 as the extended source that emits photons with energies up to
175 TeV. We compute the spectrum for HAWC J1844-034 and by comparing with the
observational results from other experiments, we have identified HESS
J1843-033, LHAASO J1843-0338, and TASG J1844-038 as very-high-energy gamma-ray
sources with a matching origin. Also, we present and use the multi-wavelength
data to fit the hadronic and leptonic particle spectra. We have identified four
pulsar candidates in the nearby region from which PSR J1844-0346 is found to be
the most likely candidate due to its proximity to HAWC J1844-034 and the
computed energy budget. We have also found SNR G28.6-0.1 as a potential
counterpart source of HAWC J1844-034 for which both leptonic and hadronic
scenarios are feasible.Comment: 13 pages, 9 figures, published in Ap
Galactic Gamma-Ray Diffuse Emission at TeV energies with HAWC Data
The Galactic gamma-ray diffuse emission (GDE) is emitted by cosmic rays
(CRs), ultra-relativistic protons and electrons, interacting with gas and
electromagnetic radiation fields in the interstellar medium. Here we present
the analysis of TeV diffuse emission from a region of the Galactic Plane over
the range in longitude of , using data collected with
the High Altitude Water Cherenkov (HAWC) detector. Spectral, longitudinal and
latitudinal distributions of the TeV diffuse emission are shown. The radiation
spectrum is compatible with the spectrum of the emission arising from a CR
population with an "index" similar to that of the observed CRs. When comparing
with the \texttt{DRAGON} \textit{base model}, the HAWC GDE flux is higher by
about a factor of two. Unresolved sources such as pulsar wind nebulae and TeV
halos could explain the excess emission. Finally, deviations of the Galactic CR
flux from the locally measured CR flux may additionally explain the difference
between the predicted and measured diffuse fluxes
HAWC and Fermi-LAT Detection of Extended Emission from the Unidentified Source 2HWC J2006+341
The discovery of the TeV point source 2HWC J2006+341 was reported in the
second HAWC gamma-ray catalog. We present a follow-up study of this source
here. The TeV emission is best described by an extended source with a soft
spectrum. At GeV energies, an extended source is significantly detected in
Fermi-LAT data. The matching locations, sizes and spectra suggest that both
gamma-ray detections correspond to the same source. Different scenarios for the
origin of the emission are considered and we rule out an association to the
pulsar PSR J2004+3429 due to extreme energetics required, if located at a
distance of 10.8 kpc.Comment: 12 pages, 2 figures. To appear in ApJ
High Altitude characterization of the Hunga Pressure Wave with Cosmic Rays by the HAWC Observatory
High-energy cosmic rays that hit the Earth can be used to study large-scale
atmospheric perturbations. After a first interaction in the upper parts of the
atmosphere, cosmic rays produce a shower of particles that sample the
atmosphere down to the detector level. The HAWC (High-Altitude Water Cherenkov)
cosmic-ray observatory in Central Mexico at 4,100 m elevation detects air
shower particles continuously with 300 water Cherenkov detectors with an active
area of 12,500 m. On January 15th, 2022, HAWC detected the passage of the
pressure wave created by the explosion of the Hunga volcano in the Tonga
islands, 9,000 km away, as an anomaly in the measured rate of shower particles.
The HAWC measurements are used to characterize the shape of four pressure wave
passages, determine the propagation speed of each one, and correlate the
variations of the shower particle rates with the barometric pressure changes,
extracting a barometric parameter. The profile of the shower particle rate and
atmospheric pressure variations for the first transit of the pressure wave at
HAWC is compared to the pressure measurements at Tonga island, near the
volcanic explosion. This work opens the possibility of using large particle
cosmic-ray air shower detectors to trace large atmospheric transient waves.Comment: Contact about this analysis: A. Sandoval ([email protected]),
A. Lara ([email protected]) & H. Le\'on Vargas
([email protected]
Limits on the Diffuse Gamma-Ray Background above 10 TeV with HAWC
The high-energy Diffuse Gamma-Ray Background (DGRB) is expected to be
produced by unresolved isotropically distributed astrophysical objects,
potentially including dark matter annihilation or decay emissions in galactic
or extragalactic structures. The DGRB has only been observed below 1 TeV; above
this energy, upper limits have been reported. Observations or stringent limits
on the DGRB above this energy could have significant multi-messenger
implications, such as constraining the origin of TeV-PeV astrophysical
neutrinos detected by IceCube. The High Altitude Water Cherenkov (HAWC)
Observatory, located in central Mexico at 4100 m above sea level, is sensitive
to gamma rays from a few hundred GeV to several hundred TeV and continuously
observes a wide field-of-view (2 sr). With its high-energy reach and large area
coverage, HAWC is well-suited to notably improve searches for the DGRB at TeV
energies. In this work, strict cuts have been applied to the HAWC dataset to
better isolate gamma-ray air showers from background hadronic showers. The
sensitivity to the DGRB was then verified using 535 days of Crab data and Monte
Carlo simulations, leading to new limits above 10 TeV on the DGRB as well as
prospective implications for multi-messenger studies.Comment: 8 pages, 3 figure
Gamma-ray Emission from Classical Nova V392 Per: Measurements from Fermi and HAWC
This paper reports on the -ray properties of the 2018 Galactic novaV392 Per, spanning photon energies 0.1 GeV to 100 TeV by combiningobservations from the Fermi Gamma-ray Space Telescope and the HAWC Observatory.In one of the most rapidly evolving -ray signals yet observed for anova, GeV rays with a power law spectrum with index were detected over eight days following V392 Per's optical maximum. HAWCobservations constrain the TeV -ray signal during this time and alsobefore and after. We observe no statistically significant evidence of TeV-ray emission from V392 Per, but present flux limits. Tests of theextension of the Fermi/LAT spectrum to energies above 5 TeV are disfavored by 2standard deviations (95\%) or more. We fit V392 Per's GeV rays withhadronic acceleration models, incorporating optical observations, and comparethe calculations with HAWC limits.<br
Gamma/Hadron Separation with the HAWC Observatory
The High Altitude Water Cherenkov (HAWC) gamma-ray observatory observesatmospheric showers produced by incident gamma rays and cosmic rays with energyfrom 300 GeV to more than 100 TeV. A crucial phase in analyzing gamma-raysources using ground-based gamma-ray detectors like HAWC is to identify theshowers produced by gamma rays or hadrons. The HAWC observatory records roughly25,000 events per second, with hadrons representing the vast majority() of these events. The standard gamma/hadron separation technique inHAWC uses a simple rectangular cut involving only two parameters. This workdescribes the implementation of more sophisticated gamma/hadron separationtechniques, via machine learning methods (boosted decision trees and neuralnetworks), and summarizes the resulting improvements in gamma/hadron separationobtained in HAWC.<br
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