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

C. B. Adams, W. Benbow, A. Brill, R. Brose, M. Buchovecky, M. Capasso, J. L. Christiansen, A. J. Chromey, M. K. Daniel, M. Errando, A. Falcone, Q. Feng, J. P. Finley, L. Fortson, A. Furniss, A. Gent, G. H. Gillanders, C. Giuri, D. Hanna, O. HervetJ. Holder, G. Hughes, T. B. Humensky, W. Jin, P. Kaaret, N. Kelley-Hoskins, M. Kertzman, D. Kieda, F. Krennrich, S. Kumar, M. J. Lang, M. Lundy, G. Maier, P. Moriarty, R. Mukherjee, D. Nieto, M. Nievas-Rosillo, S. O'Brien, R. A. Ong, A. N. Otte, K. Pfrang, M. Pohl, R. R. Prado, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, D. Ribeiro, G. T. Richards, E. Roache, J. L. Ryan, M. Santander, S. Schlenstedt, G. H. Sembroski, R. Shang, B. Stevenson, S. P. Wakely, A. Weinstein, D. A. Williams

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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 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.

Original languageEnglish (US)
Article number115
JournalAstrophysical Journal
Volume913
Issue number2
DOIs
StatePublished - Jun 1 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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