An Excess Due to Small Grains Around The Nearby K 0 V Star HD 69830 : Asteroid or Cometary Debris ?

Content Provider	Semantic Scholar
Copyright Year	2005
Abstract	Spitzer photometry and spectroscopy of the star HD 69830 reveal an excess of emission relative to the stellar photosphere between 8 and 35 m dominated by strong features attributable to crystalline silicates with an emitting surface area more than 1000 times that of our zodiacal cloud. The spectrum closely resembles that of the comet C/1995 O1 (Hale-Bopp). Since no excess is detected at 70 m, the emitting material must be quite warm, be confined within a few AU of the star, and originate in grains with low, long-wavelength emissivity, i.e., grains much smaller than 70 m/2 10 m.The strongmineralogical features are evidence for even smaller, possibly submicronsized grains. This small grain size is in direct contrast to the 10–100 m grains that dominate the relatively featureless spectra of our zodiacal dust cloud and most other main-sequence stars with excesses. The upper limit at 70 m also implies that any Kuiper Belt analog must be either very cold or less massive than 5 times our own Kuiper Belt. With collisional and Poynting-Robertson drag times of less than 1000 yr for small grains, the emitting material must either (1) be created through continual grinding down of material in a dense asteroid belt, or (2) originate in cometary debris arising from either a single ‘‘supercomet’’ or a very large number of individual comets arriving from a distant reservoir. In the case of a cometary origin for the emission, the mass requirements for continuous generation by many individual comets are unreasonable, and we favor the capture of a single super comet into a 0.5–1 AU orbit, where it can evolve a large number of small grains over a 2 Myr period. Subject headinggs: circumstellar matter — comets: general — infrared: stars — Kuiper Belt — planetary systems Online material: color figures
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Alternate Webpage(s)	http://arxiv.org/pdf/astro-ph/0504491v2.pdf
Alternate Webpage(s)	http://w.astro.berkeley.edu/~kalas/disksite/library/beichman05b.pdf
Alternate Webpage(s)	http://arxiv.org/pdf/astro-ph/0504491v1.pdf
Language	English
Access Restriction	Open
Subject Keyword	Analog Belt machine Cloud computing Comet Scoring Engine Command & Conquer:Yuri's Revenge GUCY2C protein, human Gold Greater Than Less Than Listeria monocytogenes O1 Ab:Titr:Pt:Ser:Qn Offset binary One Thousand Photometry Planetary scanner Poynting's theorem Requirement Reservoir Device Component Significant figures Silicates Small Stars, Celestial Stellar (payment network) Structure of lens capsule wavelength
Content Type	Text
Resource Type	Article