Jana Pittichová et al. 2008 The Astronomical Journal 136 1127 doi:10.1088/0004-6256/136/3/1127
GROUND-BASED OPTICAL AND SPITZER INFRARED IMAGING OBSERVATIONS OF COMET 21P/GIACOBINI-ZINNER
FREE ISSUEJana Pittichová1,2, Charles E. Woodward3, Michael S. Kelley4 and William T. Reach5
Show affiliationsWe 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, rh 
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 
7 × 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.
- Keywords
comets: individual (21P/Giacobini-Zinner); infrared: solar system; meteors, meteoroids
- Dates
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Issue 3 (2008 September)
Received 2008 April 17, accepted for publication 2008 June 20
Published 2008 August 11
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Ground-Based Optical and Spitzer Infrared Imaging Observations of Comet 21P/Giacobini-Zinner
Jana Pittichová et al. 2008 The Astronomical Journal 136 1127
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