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Titolo:
The physical basis for the silicate dust sequence
Autore:
Egan, MP; Sloan, GC;
Indirizzi:
USAF, Res Lab, Space Vehicles Directorate, Hanscom AFB, MA 01731 USA USAFHanscom AFB MA USA 01731 cles Directorate, Hanscom AFB, MA 01731 USA Boston Coll, Inst Sci Res, Chestnut Hill, MA 02467 USA Boston Coll Chestnut Hill MA USA 02467 i Res, Chestnut Hill, MA 02467 USA
Titolo Testata:
ASTROPHYSICAL JOURNAL
fascicolo: 1, volume: 558, anno: 2001,
parte:, 1
pagine: 165 - 175
SICI:
0004-637X(20010901)558:1<165:TPBFTS>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
M-MIRA VARIABLES; LATE-TYPE STARS; INFRARED-EMISSION; ALPHA-ORIONIS; CARBON STARS; EFFECTIVE TEMPERATURE; SPECTRA; FEATURES; WAVELENGTHS; CALIBRATION;
Keywords:
circumstellar matter; dust, extinction; infrared : stars;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
35
Recensione:
Indirizzi per estratti:
Indirizzo: Egan, MP USAF, Res Lab, Space Vehicles Directorate, 29 Randolph Rd, Hanscom AFB, MA01731 USA USAF 29 Randolph Rd Hanscom AFB MA USA 01731 com AFB, MA01731 USA
Citazione:
M.P. Egan e G.C. Sloan, "The physical basis for the silicate dust sequence", ASTROPHYS J, 558(1), 2001, pp. 165-175

Abstract

Using a series of radiative transfer models of circumstellar dust shells, we explore the physical origins of the variety of shapes of the 10 mum silicate feature seen in the spectra of oxygen-rich circumstellar dust shells. In order to match the full range of observed spectral shapes, the models explore four parameters: the relative abundance of amorphous alumina and amorphous silicates, the inner dust shell radius, the optical depth, and the geometric thickness of the shell. Optically thin shells dominated by amorphous silicate grains reproduce the classic narrow silicate feature at 10 mum. Increasing the optical depth of the shell produces spectral features at 10 mum with stronger components at 11 mum, but to match the [12]-[25] IRAS colors, these optically thick shells must be geometrically thin (i.e., have a truncated outer radius). Spectra with broad, low-contrast emission featurespeaking at wavelengths longer than - 11 um originate from optically thin shells composed of amorphous alumina. These findings provide a physical basis for the silicate dust sequence defined by Sloan & Price. We suggest that the [12]-[25] color is an indicator of geometric shell thickness. Thin shells can only arise if the star ejects mass and forms dust in a noncontinuousprocess.

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Documento generato il 05/12/20 alle ore 19:47:59