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H. Campins, J. Licandro, J. Guerra, M. Chamberlain, E. Pantin ()
Jupiter-family comets are of particular interest for several reasons, including the fact that they are the most accessible to spacecraft. These comets also present the best opportunities to study cometary nuclear surfaces. The characterization of cometary nuclear surfaces and their comparison with those of related populations such as extinct comet candidates, Centaurs, near-Earth asteroids, transneptunian objects and Trojan asteroids is essential to understanding the origin and evolution of these objects. Comet 28P/Neujmin 1 is among the largest and least active of the Jupiter-family comets (Campins et al. 1987, Astrophys. J. vol. 316, p. 847). We obtained low-resolution infrared spectra (0.8 to 2.4 microns) of 28P/Neujmin 1 on two occasions with the 3.56 m Telescopio Nazionale Galileo (TNG) using NICS, the near-infrared camera and spectrometer. Our first spectrum was obtained on UT June 1, 2001 (Campins et al. 2001, DPS meeting #33, #31.08) and the second spectrum on UT May 2, 2002. As expected, no detectable coma was found in comparisons of the comet images with stellar point-spread-functions. The slopes of the 2001 and 2002 infrared spectra are significantly different, with a much flatter spectrum in 2001. The spectral change appears real since no problems were detected in the solar analog stars on either date. The change we observed in the infrared spectral slope is consistent with sporadic changes in the V, R and I colors reported in this comet by Delahodde et al. (2001; Astron. and Astrophys. vol. 376, p. 672). Possible mechanisms for this spectral change will be discussed. This work was supported in part by grants from NASA and NSF.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.