Multiwavelength Observations of The TeV Binary LS I +61 303 with VERITAS, Fermi-LAT and Swift-XRT During a TeV Outburst

Abstract

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 December 2011 through January 2012 and show a strong detection in all three wavebands. During this period VERITAS obtained 24.9 hours of quality selected livetime data in which LS I +61 303 was detected at a statistical sig- nificance of 11.9 sigma. These TeV observations show evidence for nightly variability in the TeV regime at a post-trial significance of 3.6 sigma. 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 distinct populations of accelerated particles producing the GeV and TeV emission.

Accepted for Publication in ApJ

References in corpus (7)

• Gamma-ray binaries: pulsars in disguise ?
• VERITAS Observations of the gamma-Ray Binary LS I +61 303
• Unraveling the high-energy emission components of gamma-ray binaries
• Status of the VERITAS Observatory
• Associating long-term gamma-ray variability with the superorbital period of LS I 61 303
• Superorbital modulation of X-ray emission from gamma-ray binary LSI +61 303
• Swift/XRT monitoring of five orbital cycles of LSI +61 303

Cited by in corpus (11)

• Very high energy particle acceleration powered by the jets of the microquasar SS 433
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• Overview of non-transient gamma-ray binaries and prospects for the Cherenkov Telescope Array
• Exceptionally bright TeV flares from the binary LS I +61${}^{\circ }$ 303
• Galactic and Extragalactic Sources of Very High Energy Gamma-rays
• Superorbital modulation at GeV energies in the gamma-ray binary LS I +61 303
• The Multi-wavelength Characteristics of the TeV Binary LS I +61${}^{\circ }$ 303
• Understanding the periodicities in radio and GeV emission from LS I+61303
• GeV emission of gamma-ray binary with pulsar scenario
• Polarization study of gamma-ray binary
• Recent VERITAS Results