Swift-uvot grism spectroscopy of comets: A first application to C/2007 N3 (LULIN)

Abstract

We observed comet C/2007 N3 (Lulin) twice on UT 2009 January 28, using the UV grism of the Ultraviolet and Optical Telescope on board the Swift gamma-ray burst space observatory. Grism spectroscopy provides spatially resolved spectroscopy over large apertures for faint objects. We developed a novel methodology to analyze grism observations of comets, and applied a Haser comet model to extract production rates of OH, CS, NH, CN, C3, C 2, and dust. The water production rates retrieved from two visits on this date were 6.7 ± 0.7 and 7.9 ± 0.7 × 1028 molecules s-1, respectively. Jets were sought (but not found) in the white-light and "OH" images reported here, suggesting that the jets reported by Knight & Schleicher are unique to CN. Based on the abundances of its carbon-bearing species, comet Lulin is "typical" (i.e., not "depleted") in its composition. © 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A.