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Very High Energy Observations of BL Lacs

Published online by Cambridge University Press:  12 May 2006

John Quinn
Affiliation:
School of Physics, University College Dublin, Belfield, Dublin 4, Ireland email: john.quinn@ucd.ie
Peter Cogan
Affiliation:
School of Physics, University College Dublin, Belfield, Dublin 4, Ireland email: john.quinn@ucd.ie
Michael K. Daniel
Affiliation:
School of Physics, University College Dublin, Belfield, Dublin 4, Ireland email: john.quinn@ucd.ie
David J. Fegan
Affiliation:
School of Physics, University College Dublin, Belfield, Dublin 4, Ireland email: john.quinn@ucd.ie
Stephen Gammell
Affiliation:
School of Physics, University College Dublin, Belfield, Dublin 4, Ireland email: john.quinn@ucd.ie
Andrew McCann
Affiliation:
School of Physics, University College Dublin, Belfield, Dublin 4, Ireland email: john.quinn@ucd.ie
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Abstract

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The status of Very High Energy (VHE, E$\,{>}\,$50 GeV) gamma-ray observations of BL Lacertae objects is presented. The catalogue of well-established BL Lacertae objects detected at VHE energies contains seven members, and there have been recent reports of the detection of another four. All are nearby, X-ray bright sources. The temporal, spectral and broadband multi-wavelength properties of the sources are reviewed and possible implications for the gamma-ray production mechanism discussed. The most recent detections provide more stringent constraints on the cosmic extragalactic background light level and imply that the Universe is more transparent to VHE gamma radiation than previously thought.

Type
Contributed Papers
Copyright
2006 International Astronomical Union