Computer Science
Scientific paper
Aug 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000phdt........17s&link_type=abstract
Thesis (PhD). UNIVERSITY OF CALIFORNIA, LOS ANGELES, Source DAI-B 61/02, p. 893, Aug 2000, 195 pages.
Computer Science
44
Scientific paper
Excess far-infrared emission from main-sequence stars, commonly referred to as ``The Vega Phenomenon,'' is believed to be a result of thermal emission from cold dust particles orbiting in a circumstellar disk. These particles are thought to be a signature of planet formation. This study sought to characterize the nature of the Vega Phenomenon around solar-type stars. The effects of age and multiplicity were examined through sensitive far-infrared photometry of the dust emission in these systems and optical spectroscopy of the central stars. A survey consisting of 146 observations was performed with ISOPhot at 60 and 90 or 100μm. Excess emission was detected from 44 targets, above a typical noise level of 20mJy. Ages of stars in our sample were determined with optical high-resolution spectroscopy of the Ca-II H and K lines, and was supplemented by published age estimates. Our photometry also revealed that 7 of 25 targets with previously measured far-infrared excess are due to background cirrus confusion, rather than a measurement of circumstellar dust. Results indicate that the decrease of infrared excess with stellar age is consistent with the dust disk mass decrease with time-1.75 , determined for nearby open clusters with ages spanning 10 7 to 109 years. Furthermore, the use of far-infrared excess as an indicator of stellar youth is demonstrated. Our results further suggest that the presence of a close stellar companion affects the amount of far-infrared excess. Stars with closer binary companions have less dust than single stars or those in wide binary orbits. In this work we have constrained the role of colliding planetesimals in the evolution of circumstellar disks. Future studies will build upon these early steps in the observation and understanding planet- forming systems.
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