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James L Ryan

Publications and source records attributed to James L Ryan.

2 recordsLinked to original sources
arXiv2023

Search for Dark Matter Annihilation Signals in the Galactic Center Halo with VERITAS

Gamma-ray observations of the Galactic Center (GC) region provide some of the most sensitive measurements of annihilation signals from dark matter in the GeV-TeV mass range. We present the first results from 178 hours of VERITAS observations of a 2 degree region around the GC, taken between 2010 and 2022. The analysis uses a newly-developed template-based background method, as well as analysis techniques optimized for observations taken at large zenith angles. No significant excess is found in any region of interest considered. We derive model-independent limits on the dark matter thermally-averaged annihilation cross section which are among the strongest from any indirect detection experiment for TeV-scale masses.

astro-ph.HE↗
arXiv2021

VERITAS Observations of the Galactic Center Region at Multi-TeV Gamma-Ray Energies

The Galactic Center region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of non-thermal radiation. We present the analysis of the very-high-energy gamma-ray emission above 2 TeV of the region around the Galactic Center known as the Central Molecular Zone using 125 hours of data taken with the VERITAS imaging-atmospheric Cherenkov telescope between 2010 and 2018. This analysis employs new shower reconstruction algorithms and instrument response functions optimized for data taken at large zenith angles such as the Galactic Center sources. We report positions and spectra for point sources VER J1745-290, G0.9+0.1, and HESS J1746-285, along with a light curve for VER J1745-290, the brightest source in the region consistent with the position of the supermassive black hole Sagittarius A*. We also measure the spectrum of the diffuse emission from the Galactic Center ridge region, which has been claimed as evidence of a Galactic PeVatron.

astro-ph.HE↗