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Flat spectrum T Tauri stars: The case for infallWe show that the mid- to far-infrared fluxes of 'flat spectrum' T Tauri stars can be explained by radiative equilibrium emission from infalling dusty envelopes. Infall eliminates the need for accretion disks with non-standard temperature distributions. The simplicity and power of this explanantion indicates that models employing 'active' disks, in which the temperature distribution is a parameterized power law, should be invoked with caution. Infall also naturally explains the scattered light nebulae detected around many flat spectrum sources. To match the observed spectra, material must fall onto a disk rather than the central star, as expected for collapse of a rotating molecular cloud. It may be necessary to invoke cavities in the envelopes to explain the strength of optical and near-infrared emission; these cavities could be produced by the powerful bipolar outflows commonly observed from young stars. If viewed along the cavity, a source may be lightly extincted at visual wavelengths, while still accreting substantial amounts of material from the envelope. Infall may also be needed to explain the infrared-bright companions of many optical T Tauri stars. This picture suggests that many of the flat spectrum sources are 'protostars'-young stellar objects surrounded by dust infalling envelopes of substantial mass.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Calvet, Nuria (Centro de Investigaciones de Astronomia Merida, Venezuela)
Hartmann, Lee (Center for Astrophysics, Cambridge, MA United States)
Kenyon, S. J. (Center for Astrophysics, Cambridge, MA United States)
Whitney, B. A. (Center for Astrophysics, Cambridge, MA United States)
Date Acquired
August 16, 2013
Publication Date
October 10, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 434
Issue: 1
ISSN: 0004-637X
Subject Category
Funding Number(s)
Distribution Limits