Journal article
Discovery of Variability in the Very High Energy Gamma-Ray Emission of 1ES 1218+304 with VERITAS
Astrophysical journal. Letters, Vol.709(2), pp.L163-L167
01/14/2010
DOI: 10.1088/2041-8205/709/2/L163
Abstract
We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured spectra for absorption by the extragalactic background light, 1ES 1218+304 and a number of other blazars are found to have differential photon indices less than 1.5. The difficulty in modeling these hard spectral energy distributions in blazar jets has led to a range of theoretical gamma-ray emission scenarios, one of which is strongly constrained by these new VERITAS observations. We consider the implications of the observed light curve of 1ES 1218+304, which shows day scale flux variations, for shock acceleration scenarios in relativistic jets, and in particular for the viability of kiloparsec-scale jet emission scenarios.
Details
- Title: Subtitle
- Discovery of Variability in the Very High Energy Gamma-Ray Emission of 1ES 1218+304 with VERITAS
- Creators
- VERITAS
- Contributors
- Philip E Kaaret (Contributor) - University of Iowa, Physics and Astronomy
- Resource Type
- Journal article
- Publication Details
- Astrophysical journal. Letters, Vol.709(2), pp.L163-L167
- DOI
- 10.1088/2041-8205/709/2/L163
- ISSN
- 1538-4357
- eISSN
- 2041-8213
- Publisher
- The American Astronomical Society
- Grant note
- unidentified / Natural Sciences and Engineering Research Council of Canada (nserc_______::NSERC)
- Language
- English
- Date published
- 01/14/2010
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199703702771
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