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American Astronomical Society, Astrophysical Journal, 2(913), p. 115, 2021

DOI: 10.3847/1538-4357/abf926

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021), 2021

DOI: 10.22323/1.395.0833

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

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Preprint: archiving forbidden
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Postprint: archiving forbidden
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Data provided by SHERPA/RoMEO

Abstract

Abstract The Galactic Center (GC) region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of nonthermal radiation. The inner 375 pc × 600 pc region, called the Central Molecular Zone, is home to the supermassive black hole Sagittarius A*, massive cloud complexes, and particle accelerators such as supernova remnants (SNRs). We present the results of our improved analysis of the very-high-energy gamma-ray emission above 2 TeV from the GC using 125 hr of data taken with the Very Energetic Radiation Imaging Telescope Array System imaging-atmospheric Cerenkov telescope between 2010 and 2018. The central source VER J1745–290, consistent with the position of Sagittarius A*, is detected at a significance of 38 standard deviations above the background level (38σ), and we report its spectrum and light curve. Its differential spectrum is consistent with a power law with exponential cutoff, with a spectral index of , a flux normalization at 5.3 TeV of TeV−1 cm−2 s−1, and cutoff energy of TeV. We also present results on the diffuse emission near the GC, obtained by combining data from multiple regions along the GC ridge, which yield a cumulative significance of 9.5σ. The diffuse GC ridge spectrum is best fit by a power law with a hard index of 2.19 ± 0.20, showing no evidence of a cutoff up to 40 TeV. This strengthens the evidence for a potential accelerator of PeV cosmic rays being present in the GC. We also provide spectra of the other sources in our field of view with significant detections, composite SNR G0.9+0.1, and HESS J1746–285.