71 research outputs found
Measurement of the Crab Nebula Spectrum Past 100 TeV with HAWC
We present TeV gamma-ray observations of the Crab Nebula, the standard
reference source in ground-based gamma-ray astronomy, using data from the High
Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory. In this analysis we use
two independent energy-estimation methods that utilize extensive air shower
variables such as the core position, shower angle, and shower lateral energy
distribution. In contrast, the previously published HAWC energy spectrum
roughly estimated the shower energy with only the number of photomultipliers
triggered. This new methodology yields a much improved energy resolution over
the previous analysis and extends HAWC's ability to accurately measure
gamma-ray energies well beyond 100 TeV. The energy spectrum of the Crab Nebula
is well fit to a log parabola shape with emission up to at least 100 TeV. For the first
estimator, a ground parameter that utilizes fits to the lateral distribution
function to measure the charge density 40 meters from the shower axis, the
best-fit values are
=(2.350.04)10 (TeV cm
s), =2.790.02, and
=0.100.01. For the second estimator, a neural
network which uses the charge distribution in annuli around the core and other
variables, these values are
=(2.310.02)10 (TeV cm
s), =2.730.02, and
=0.060.010.02. The first set of uncertainties are statistical;
the second set are systematic. Both methods yield compatible results. These
measurements are the highest-energy observation of a gamma-ray source to date.Comment: published in Ap
Constraining the local burst rate density of primordial black holes with HAWC
Primordial Black Holes (PBHs) may have been created by density fluctuations in the early Universe and could be as massive as \u3e 109 solar masses or as small as the Planck mass. It has been postulated that a black hole has a temperature inversely-proportional to its mass and will thermally emit all species of fundamental particles via Hawking Radiation. PBHs with initial masses of ∼ 5 × 1014 g (approximately one gigaton) should be expiring today with bursts of high-energy gamma radiation in the GeV-TeV energy range. The High Altitude Water Cherenkov (HAWC) Observatory is sensitive to gamma rays with energies of ∼300 GeV to past 100 TeV, which corresponds to the high end of the PBH burst spectrum. With its large instantaneous field-of-view of ∼ 2 sr and a duty cycle over 95%, the HAWC Observatory is well suited to perform an all-sky search for PBH bursts. We conducted a search using 959 days of HAWC data and exclude the local PBH burst rate density above 3400 pc-3 yr-1 at 99% confidence, the strongest limit on the local PBH burst rate density from any existing electromagnetic measurement
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
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
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]
Constraints on the very high energy gamma-ray emission from short GRBs with HAWC
Many gamma-ray bursts (GRBs) have been observed from radio wavelengths, and afew at very-high energies (VHEs, > 100GeV). The HAWC gamma-ray observatory iswell suited to study transient phenomena at VHEs due to its large field of viewand duty cycle. These features allow for searches of VHE emission and can probedifferent model assumptions of duration and spectra. In this paper, we use datacollected by HAWC between December 2014 and May 2020 to search for emission inthe energy range from 80 to 800 GeV coming from a sample 47 short GRBs thattriggered the Fermi, Swift and Konus satellites during this period. Thisanalysis is optimized to search for delayed and extended VHE emission withinthe first 20 s of each burst. We find no evidence of VHE emission, eithersimultaneous or delayed, with respect to the prompt emission. Upper limits (90%confidence level) derived on the GRB fluence are used to constrain thesynchrotron self-Compton forward-shock model. Constraints for the interstellardensity as low as cm are obtained when assuming z=0.3 forbursts with the highest keV-fluences such as GRB 170206A and GRB 181222841.Such a low density makes observing VHE emission mainly from the fast coolingregime challenging.<br
Constraints on the Emission of Gamma-Rays from M31 with HAWC
Cosmic rays, along with stellar radiation and magnetic fields, are known to make up a significant fraction of the energy density of galaxies such as the Milky Way. When cosmic rays interact in the interstellar medium, they produce gamma-ray emission which provides an important indication of how the cosmic rays propagate. Gamma-rays from the Andromeda galaxy (M31), located 785 kpc away, provide a unique opportunity to study cosmic-ray acceleration and diffusion in a galaxy with a structure and evolution very similar to the Milky Way. Using 33 months of data from the High Altitude Water Cherenkov Observatory, we search for teraelectronvolt gamma-rays from the galactic plane of M31. We also investigate past and present evidence of galactic activity in M31 by searching for Fermi bubble-like structures above and below the galactic nucleus. No significant gamma-ray emission is observed, so we use the null result to compute upper limits on the energy density of cosmic rays >10 TeV in M31
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