Gamma-Ray Observations of Tycho’s Supernova Remnant with VERITAS and Fermi

Journal Article · Fri Feb 10 04:00:00 EST 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/836/1/23· OSTI ID:22663882

Archambault, S.; Bourbeau, E.; Feng, Q.; Griffin, S. ^[1]; Archer, A.; Buckley, J. H.; Bugaev, V.; Errando, M. ^[2]; Benbow, W.; Cerruti, M. ^[3]; Bird, R.; Buchovecky, M. ^[4]; Connolly, M. P. ^[5]; Cui, W.; Finley, J. P. ^[6]; Dwarkadas, V. V. ^[7]; Falcone, A. ^[8]; Fleischhack, H. ^[9]; Fortson, L. ^[10]; others, and

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1. Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada)
2. Department of Physics, Washington University, St. Louis, MO 63130 (United States)
3. Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States)
4. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)
5. School of Physics, National University of Ireland Galway, University Road, Galway (Ireland)
6. Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States)
7. Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States)
8. Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States)
9. DESY, Platanenallee 6, D-15738 Zeuthen (Germany)
10. School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)

High-energy gamma-ray emission from supernova remnants (SNRs) has provided a unique perspective for studies of Galactic cosmic-ray acceleration. Tycho’s SNR is a particularly good target because it is a young, type Ia SNR that has been well-studied over a wide range of energies and located in a relatively clean environment. Since the detection of gamma-ray emission from Tycho’s SNR by VERITAS and Fermi -LAT, there have been several theoretical models proposed to explain its broadband emission and high-energy morphology. We report on an update to the gamma-ray measurements of Tycho’s SNR with 147 hr of VERITAS and 84 months of Fermi -LAT observations, which represent about a factor of two increase in exposure over previously published data. About half of the VERITAS data benefited from a camera upgrade, which has made it possible to extend the TeV measurements toward lower energies. The TeV spectral index measured by VERITAS is consistent with previous results, but the expanded energy range softens a straight power-law fit. At energies higher than 400 GeV, the power-law index is 2.92 ± 0.42{sub stat} ± 0.20{sub sys}. It is also softer than the spectral index in the GeV energy range, 2.14 ± 0.09{sub stat} ± 0.02{sub sys}, measured in this study using Fermi -LAT data. The centroid position of the gamma-ray emission is coincident with the center of the remnant, as well as with the centroid measurement of Fermi -LAT above 1 GeV. The results are consistent with an SNR shell origin of the emission, as many models assume. The updated spectrum points to a lower maximum particle energy than has been suggested previously.

• OSTI ID: 22663882
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 836; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
COSMIC GAMMA SOURCES
COSMIC RADIATION
DETECTION
EMISSION
GAMMA RADIATION
GEV RANGE
SPECTRA
SUPERNOVA REMNANTS
SUPERNOVAE
TEV RANGE