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| Paper: |
Multiwavelength Observations of 3C 66A in 2003-2004 |
| Volume: |
350, Blazar Variability Workshop II: Entering the GLAST Era |
| Page: |
8 |
| Authors: |
Boettcher, M. |
| Abstract: |
The BL Lac object 3C 66A was the target of an extensive multiwavelength campaign from July 2003 through April 2004. Radio, infrared, and optical observations were carried out by the WEBT-ENIGMA collaboration. At higher energies, 3C 66A was observed in X-rays (RXTE), and at very-high-energy (VHE) γ-rays (STACEE, VERITAS). In addition, the source has been observed with the VLBA at 9 epochs throughout the period September 2003 – December 2004, including 3 epochs contemporaneous with the core campaign.
The source was in an optically bright state, with several bright flares on time scales of several days and microvariability with flux changes of ∼ 5 % on time scales as short as ∼ 2 hr. Spectral variability indicating a softening throughout both the rising and decaying phases of flares, has been found.
The spectral energy distribution (SED) indicates a vFv peak in the optical regime. The 3 – 10 keV X-ray flux of 3C 66A during the core campaign was historically high and its spectrum very soft, indicating that the low-frequency component of the broadband SED extends beyond ∼ 10 keV. No significant X-ray flux and/or spectral variability was detected. STACEE and Whipple observations provided upper flux limits at > 150 GeV and > 390 GeV, respectively.
The 22 and 43 GHz VLBA data indicate a rather smooth jet with only moderate internal structure. Evidence for superluminal motion (8.5±5.6 h−1 c) was found in only one out of 6 components, while all other components are consistent with 0 proper motion. The radial brightness profile suggests a magnetic field decay ∝ r−1 and, thus, a predominantly perpendicular magnetic field orientation. |
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