The very high energy gamma ray spectra of IES 1959+650 and Mrk 421 as measured with the Whipple 10 m telescope
- Department of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160 (United States)
- and others
In observations made with the Whipple 10 m telescope, 1ES 1959+650 (z 0.048) was caught in a high flaring state in May 2002, concurrent with a high X-ray state, and in June 2002, for which there was no corresponding X-ray flare. The spectra for both of those occasions are well fitted by a power law of differential spectral index {approx} -2.8. The relative stability of the spectral index for those flares argues strongly in favour of a two-component model as to the emission zones for the two radiation regimes.Markarian 421 (z = 0.031) was observed to be in a high flaring state, at levels of {>=} 3 Crab, during March and April 2004. The average spectrum over this time period shows evidence for a cut-off in the spectrum at {approx} 5 TeV, similar to a cut-off seen during an equivalently strong episode of flaring activity in 2001. The continued appearance of this feature indicates a long term stability, either in the physical conditions at the source, or in the intervening medium (such as attenuation on the extra-galactic infra-red background radiation)
- OSTI ID:
- 20630532
- Journal Information:
- AIP Conference Proceedings, Vol. 745, Issue 1; Conference: 2. international symposium on high energy gamma-ray astronomy, Heidelberg (Germany), 26-30 Jul 2004; Other Information: DOI: 10.1063/1.1878446; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); VERITAS collaboration; ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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