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Title: Multiwavelength observations of the TeV binary LS I +61° 303 with Veritas, Fermi-LAT, and Swift/xrt during a TeV outburst

We present the results of a multiwavelength observational campaign on the TeV binary system LS I +61° 303 with the VERITAS telescope array (>200 GeV), Fermi-LAT (0.3-300 GeV), and Swift/XRT (2-10 keV). The data were taken from 2011 December through 2012 January and show a strong detection in all three wavebands. During this period VERITAS obtained 24.9 hr of quality selected livetime data in which LS I +61° 303 was detected at a statistical significance of 11.9σ. These TeV observations show evidence for nightly variability in the TeV regime at a post-trial significance of 3.6σ. The combination of the simultaneously obtained TeV and X-ray fluxes do not demonstrate any evidence for a correlation between emission in the two bands. For the first time since the launch of the Fermi satellite in 2008, this TeV detection allows the construction of a detailed MeV-TeV spectral energy distribution from LS I +61° 303. This spectrum shows a distinct cutoff in emission near 4 GeV, with emission seen by the VERITAS observations following a simple power-law above 200 GeV. This feature in the spectrum of LS I +61° 303, obtained from overlapping observations with Fermi-LAT and VERITAS, may indicate that there are two distinctmore » populations of accelerated particles producing the GeV and TeV emission.« less
Authors:
 [1] ;  [2] ; ; ;  [3] ;  [4] ; ;  [5] ; ; ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ; ; ;  [11] ;  [12] ;  [13] more »; « less
  1. Physics Department, Columbia University, New York, NY 10027 (United States)
  2. Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada)
  3. DESY, Platanenallee 6, D-15738 Zeuthen (Germany)
  4. Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States)
  5. Department of Physics, Washington University, St. Louis, MO 63130 (United States)
  6. Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States)
  7. School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)
  8. Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States)
  9. Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States)
  10. School of Physics, National University of Ireland Galway, University Road, Galway (Ireland)
  11. Department of Physics, Purdue University, West Lafayette, IN 47907 (United States)
  12. School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)
  13. Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States)
Publication Date:
OSTI Identifier:
22348508
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; BINARY STARS; CORRELATIONS; DETECTION; EMISSION; ENERGY SPECTRA; GAMMA RADIATION; GEV RANGE; KEV RANGE; MEV RANGE; RELATIVISTIC RANGE; SATELLITES; STARS; TELESCOPES; TEV RANGE; X RADIATION