1ES0806+524 - Discovery of a new VHE Blazar
Reference: V. A. Acciari et al. (The VERITAS Collaboration), The Astrophysical Journal, 690: L126, 2009
Full text version
ArXiv version: ArXiV:0812.0978
Contact person: Peter Cogan
1ES 0806+524 is a blazar located at a redshift of 0.138. This blazar was identified as a candidate source of very-high energy gamma-ray emission based on the presence of both high-energy electrons and sufficient seed photons. Theoretical studies predict a flux of 1.36×10-11 cm-2 s-1 above 0.3 TeV (but it was detected by VERITAS at the significantly lower flux of 4.4×10-12 cm-2 s-1). 1ES 0806+524 was observed by VERITAS while the array was being constructed in the 2006/2007 observing season (and thus used fewer than four telescopes) and after it was complete during the 2007/2008 observing season. The blazar was observed for a total of 65 hours (after quality cuts for weather and detector performance). The peak source location of the gamma-ray excess is RA=8h9m59s and DEC=52o19'2" which is statistically consistent with the known blazar position.
Using only the higher-quality four-telescope data, the energy spectrum is fit to the form dN/dE=F×(E/400GeV)-Γ where F=6.8±1.7 (stat)±1.3 (sys) 10-12 cm-2 s-1 and Γ=3.6±1(stat)±0.3(sys). Absorption on the infrared component of the extragalactic background light softens the spectral index. The spectrum can be deabsorbed giving an
intrinsic spectral index of 2.8±0.5 (stat). No variability is found on monthly timescales.
Following the announcement by VERITAS of the detection of very-high energy gamma-ray emission from 1ES 0806+524, observations of the blazar were performed using the Swift telescope in the ultraviolet to optical and X-ray energy bands. These data are combined with an archival (non-contemporaneous) data point from the Tuorla observatory to create a broad-band spectral energy distribution. This is modeled using a one-zone jet radiation transfer code. The synchrotron peak is located at 8.3×1015 Hz and the inverse-Compton peak is located at 3.5×1024 Hz.
Figures from paper (click to get full size image):