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Particle emissivity in circumstellar disks
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1991
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Submillimeter continuum observations of 29 pre‑main‑sequence T Tauri stars in Taurus and Orion are used to study the wavelength dependence of particle emission from their circumstellar disks. Assuming optically thin emission, particle emissivities follow power‑law indices between –1 and 1, and variations in particle shape and composition can account for the observed behavior. The measured flux densities yield spectral indices between 2 and 3, indicating that the emission is largely optically thin near 1 mm; these indices are smaller than those of the diffuse interstellar medium, implying larger millimeter‑wave opacities and a reduced amount of disk material needed to produce the observed continuum. Published in The Astrophysical Journal (Nov 1991, DOI 10.1086/170646).
view Abstract Citations (482) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Particle Emissivity in Circumstellar Disks Beckwith, Steven V. W. ; Sargent, Anneila I. Abstract Submillimeter continuum observations of 29 pre-main-sequence objects in Taurus and Orion are used to study the wavelength dependence of particle emission. These objects are mostly T Tauri stars whose long-wavelength emission is thought to originate in circumstellar disks. The flux densities imply power-law frequency distributions with spectral indices between two and three in almost all cases. If the emission is optically thin, the particle emissivities have power-law indices between -1 and 1; otherwise, these values are lower limits. It is argued that in most cases the emission is optically thin at wavelengths near 1 mm, so the measured indices should be close to the true values. The indices derived for the circumstellar particles are substantially smaller than those thought to obtain in the diffuse interstellar medium and dense molecular clouds; they imply that the millimeter-wave opacities are larger near these stars than in the interstellar medium. Particle shape and composition changes can produce the observed behavior. The effect is to decrease the required amount of disk material needed to produce the observed millimeter-wave continuum emission. Publication: The Astrophysical Journal Pub Date: November 1991 DOI: 10.1086/170646 Bibcode: 1991ApJ...381..250B Keywords: Particle Emission; Shell Stars; Stellar Mass Ejection; Millimeter Waves; Pre-Main Sequence Stars; Radio Stars; T Tauri Stars; Astrophysics; STARS: CIRCUMSTELLAR SHELLS; STARS: MASS LOSS; STARS: PRE--MAIN-SEQUENCE full text sources ADS | data products SIMBAD (37)