Rotation of the Nucleus, Gas Kinematics and Emission Pattern of Comet 8P/Tuttle: Preliminary Results from Optical Imaging of the CN Coma

We present preliminary results of the narrow-band CN observations of comet 8P/Tuttle from early January 2008, realized as part of a project consisting of near-simultaneous spectroscopic monitoring of HCN at millimeter-wavelengths and optical imaging of the coma. The mean-image subtraction method revealed low-contrast CN envelopes. Using the image cross-correlation technique we measured the projected velocity of these shells. For the sunward part we found it to be equal to 0.96 ± 0.03 km s^?1 on January 4 and 1.10 ± 0.01 km s^?1 on January 9, whereas the anti-sunward part reached 0.73 ± 0.05 and 0.80 ± 0.02 km s^?1, respectively. The periodicity of gas emission was investigated using a repeatability of the shells, their kinematics, and an aperture photometry of the near nucleus region. We found a period of 5.70 ± 0.07 h (along with multiples), consistent with previous findings by other authors. A toy Monte Carlo model was implemented to reproduce the time-series of the CN images. We show that emission of HCN into a relatively wide cone by a single active region on a rotating nucleus is the most probable scenario.