Pittichová, Jana and Woodward, Charles E. and Kelleypitti, Michael S. and Reach, William T. (2008) Ground-based optical and Spitzer infrared imaging observations of comet 21p/Giacobini-Zinner. Astronomical Journal, 136 (3). pp. 1127-1136. ISSN 0004-6256 http://resolver.caltech.edu/CaltechAUTHORS:PITaj08
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We present ground-based optical and Spitzer Space Telescope infrared (IR) imaging observations of the ecliptic (Jupiter-family) comet 21P/Giacobini-Zinner, the parent body of the Draconid meteor stream, during its 2005 apparition. The onset of nucleus activity occurred at a pre-perihelion heliocentric distance, r(h) ≃ 3.80 AU, while post-perihelion 21P was dusty (peak Afρ = 131 cm^(-1)) and active out to heliocentric distances ≳ 3.3 AU following a logarithmic slope with rh of -2.04. Coma colors, V-R = 0.524 ± 0.003, R-I = 0.487 ± 0.004, are redder than solar, yet comparable to colors derived for other Jupiter-family comets. A nucleus radius of 1.82 ± 0.05 km is derived from photometry at quiescence. Spitzer images post-perihelion exhibit an extensive coma with a prominent dust tail, where excess emission (over the dust continuum) in the 4.5 µm Infrared Array Camera ( IRAC) image arises from volatile gaseous CO and/or CO2. No dust trail was detected (3σ surface brightness upper limit of 0.3 MJy sr^(-1) pixel^(-1)) along the projected velocity vector of comet 21P in the MIPS 24 µm image suggesting that the number density of trail particles is less than or similar to 7 x 10^(-11) m^(-3). The bolometric albedo of 21P derived from the contemporaneous optical and Spitzer observations is A(θ = 22°) = 0.11, slightly lower than values derived for other comets at the same phase angle.
|Additional Information:||© 2008 American Astronomical Society. Received 2008 April 17; accepted 2008 June 20; published 2008 August 11. Print publication: Issue 3 (2008 September). This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. Support for this work was also provided by NASA through contracts 123741, 127835, and 1256406 issued by JPL/Caltech to the University of Minnesota. C.E.W. acknowledges support from the National Science Foundation grant AST-0706980. M.S.K. acknowledges support from the University of Minnesota Doctoral Dissertation Fellowship. J.P. was supported, in part, by the NASA Planetary Astronomy Program, and by NASA through contract 1278383 issued by JPL/Caltech to the University of Hawaii and the Scientific Grant Agency VEGA of the Slovak Academy of Sciences, 2/4002/04. The authors wish to thank Dr. Karen Meech for her insightful discussions, as well as an anonymous referee whose comments and suggestions improved the clarity of this manuscript. Facilities: Spitzer (IRAC, MIPS) UH 2.2m (Tek2048 CCD)|
|Subject Keywords:||comets: individual (21P/Giacobini-Zinner); infrared: solar system; meteors, meteoroids|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||15 Jan 2009 21:38|
|Last Modified:||26 Dec 2012 10:35|
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