A Spitzer Infrared Spectrograph Detection of Crystalline Silicates in a Protostellar Envelope

We present the Spitzer Space Telescope Infrared Spectrograph spectrum of the Orion A protostar HOPS-68. The mid-infrared spectrum reveals crystalline substructure at 11.1, 16.1, 18.8, 23.6, 27.9, and 33.6 {mu}m superimposed on the broad 9.7 and 18 {mu}m amorphous silicate features; the substructure...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2011-06, Vol.733 (2), p.L32
Main Authors: Poteet, Charles A, Megeath, S. Thomas, Watson, Dan M, Calvet, Nuria, Remming, Ian S, McClure, Melissa K, Sargent, Benjamin A, Fischer, William J, Furlan, Elise, Allen, Lori E, Bjorkman, Jon E, Hartmann, Lee, Muzerolle, James, Tobin, John J, Ali, Babar
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BINARY STARS
DETECTION
ENERGY TRANSFER
ERUPTIVE VARIABLE STARS
HEAT TRANSFER
INFRARED SPECTRA
MASS
MINERALS
OLIVINE
OXYGEN COMPOUNDS
PROTOSTARS
RADIANT HEAT TRANSFER
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SPECTRA
STARS
T TAURI STARS
VARIABLE STARS
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Summary:We present the Spitzer Space Telescope Infrared Spectrograph spectrum of the Orion A protostar HOPS-68. The mid-infrared spectrum reveals crystalline substructure at 11.1, 16.1, 18.8, 23.6, 27.9, and 33.6 {mu}m superimposed on the broad 9.7 and 18 {mu}m amorphous silicate features; the substructure is well matched by the presence of the olivine end-member forsterite (Mg{sub 2}SiO{sub 4}). Crystalline silicates are often observed as infrared emission features around the circumstellar disks of Herbig Ae/Be stars and T Tauri stars. However, this is the first unambiguous detection of crystalline silicate absorption in a cold, infalling, protostellar envelope. We estimate the crystalline mass fraction along the line of sight by first assuming that the crystalline silicates are located in a cold absorbing screen and secondly by utilizing radiative transfer models. The resulting crystalline mass fractions of 0.14 and 0.17, respectively, are significantly greater than the upper limit found in the interstellar medium ({approx}
ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/733/2/L32