Physical observations of comets: Their composition, origin and evolution

Observations of Comet P/Schwassmann-Wachmann 1 (SW1) during one observing run each in 1989 and 1990 are discussed, and the new significant information that was obtained is presented. Also discussed are near-UV observations of comets. The near-UV is a mostly unexplored spectral region for comets since it is not visible to spacecraft such as IUE and most ground-based detectors and spectrographs are not sensitive in the near-UV

Physical observations of comets: Their composition, origin and evolution

The composition, origins, and evolution of comets were studied. The composition was studied using spectroscopic observations of primarily brighter comets at moderate and high resolution for the distribution of certain gases in the coma. The origins was addressed through an imaging search for the Kuiper belt of comets. The evolution was addressed by searching for a link between comets and asteroids using an imaging approach to search for an OH coma

Observations of O (1S) and O (1D) in Spectra of C/1999 S4 (LINEAR)

We report on high spectral resolution observations of comet C/1999 S4 (LINEAR) obtained at McDonald Observatory in June and July 2000. We report unequivocal detections of the O (1S) and O (1D) metastable lines in emission in the cometary spectrum. These lines are well separated from any telluric or cometary emission features. We have derived the ratio of the two red doublet lines and show they are consistent with the predictions of the branching ratio. We also derived a ratio of 0.06+/-0.01 for the green line flux to the sum of the red line fluxes. This ratio is consistent with H2O as the dominant parent for atomic oxygen. We have measured the widths of the lines and show that the widths imply that there must be some parent of atomic oxygen in addition to the H2O.Comment: 26 pages includes 6 figures and 3 tables; accepted for Icaru

The Spatial Distribution Of OH And CN Radicals In The Coma Of Comet Encke

Multiple potential parent species have been proposed to explain CN abundances in comet comae, but the parent has not been definitively identified for all comets. This study examines the spatial distribution of CN radicals in the coma of comet Encke and determines the likelihood that CN is a photodissociative daughter of HCN in the coma. Comet Encke is the shortest orbital period (3.3 years) comet known and also has a low dust-to-gas ratio based on optical observations. Observations of CN were obtained from 2003 October 22 to 24, using the 2.7 m telescope at McDonald Observatory. To determine the parent of CN, the classical vectorial model was modified by using a cone shape in order to reproduce Encke's highly aspherical and asymmetric coma. To test the robustness of the modified model, the spatial distribution of OH was also modeled. This also allowed us to obtain CN/OH ratios in the coma. Overall, we find the CN/OH ratio to be 0.009 +/- 0.004. The results are consistent with HCN being the photodissociative parent of CN, but we cannot completely rule out other possible parents such as CH(3)CN and HC(3)N. We also found that the fan-like feature spans similar to 90 degrees, consistent with the results of Woodney et al..NASAOffice of the Vice President for Research and Economic Development at Mississippi State UniversityMcDonald Observator

The Spin-Orbit Alignment of the HD17156 Transiting Eccentric Planetary System

We present high precision radial velocity observations of HD17156 during a transit of its eccentric Jovian planet. In these data, we detect the Rossiter-McLaughlin effect, which is an apparent perturbation in the velocity of the star due to the progressive occultation of part of the rotating stellar photosphere by the transiting planet. This system had previously been reported by Narita et al. (2008) to exhibit a lambda = 62 +/- 25 degree misalignment of the projected planetary orbital axis and the stellar rotation axis. We model our data, along with the Narita et al. data, and obtain lambda = 9.4 +/- 9.3 degrees for the combined data set. We thus conclude that the planetary orbital axis is actually very well aligned with the stellar rotation axis.Comment: 4 pages, 1 figure, Ap.J. Letters in pres