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Discovery of >100 GeV Gamma-ray Emission from the Blazar 3C66A by VERITAS

ATEL # 1753; Simon Swordy for the VERITAS collaboration
on 1 Oct 2008; 21:43 UT
Password Certification: Simon Swordy (

Subjects: >GeV, Request for Observations, AGN
Referred to by ATEL #: 1755, 1759

The VERITAS collaboration reports the discovery of very high-energy gamma-ray emission from the intermediate-frequency-peaked BL Lac object 3C66A with the VERITAS array of four 12 m imaging atmospheric Cherenkov telescopes (Mt. Hopkins, Az). This blazar was detected by EGRET and is likely to be detected by the recently launched Fermi Gamma-ray Space Telescope. Even though this is a well-known AGN, its redshift is uncertain (see Bramel et al., 2005, ApJ, 629, 108 and Finke et al., 2008, A&A, 447, 513). 3C66A appears to be in an active state since at least Sept. 25, 2008 when VERITAS started observing it, resulting in a highly significant detection (> 8 standard deviations). The gamma-ray spectrum is soft, and the integral gamma-ray flux above 100 GeV is about 0.1 Crab. The VERITAS array will continue to observe 3C66A this month. Up to date information regarding the VERITAS observation schedule for this source will be available at the website below. Multi-wavelength observations across the electromagnetic spectrum are strongly encouraged. In particular, redshift measurements would be highly valuable given the possible implications of the detection of this gamma-ray source for extragalactic background light (EBL) studies.

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