1,141 research outputs found
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
Validation of standardized data formats and tools for ground-level particle-based gamma-ray observatories
Ground-based gamma-ray astronomy is still a rather young field of research,with strong historical connections to particle physics. This is why mostobservations are conducted by experiments with proprietary data and analysissoftware, as it is usual in the particle physics field. However in recentyears, this paradigm has been slowly shifting towards the development and useof open-source data formats and tools, driven by upcoming observatories such asthe Cherenkov Telescope Array (CTA). In this context, a community-driven,shared data format (the gamma-astro-data-format or GADF) and analysis toolssuch as Gammapy and ctools have been developed. So far these efforts have beenled by the IACT community, leaving out other types of ground-based gamma-rayinstruments.We aim to show that the data from ground particle arrays, such asthe High-Altitude Water Cherenkov (HAWC) observatory, is also compatible withthe GADF and can thus be fully analysed using the related tools, in this caseGammapy. We reproduce several published HAWC results using Gammapy and dataproducts compliant with GADF standard. We also illustrate the capabilities ofthe shared format and tools by producing a joint fit of the Crab spectrumincluding data from six different gamma-ray experiments. We find excellentagreement with the reference results, a powerful check of both the publishedresults and the tools involved. The data from particle detector arrays such asthe HAWC observatory can be adapted to the GADF and thus analysed with Gammapy.A common data format and shared analysis tools allow multi-instrument jointanalysis and effective data sharing. Given the complementary nature of pointingand wide-field instruments, this synergy will be distinctly beneficial for thejoint scientific exploitation of future observatories such as the SouthernWide-field Gamma-ray Observatory and CTA.<br
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]
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
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
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