Accretion as an energy source for pre-main sequence stars

  • Scott J. Kenyon
Exploiting the Infrared
Part of the Lecture Notes in Physics book series (LNP, volume 291)


The strongest argument that accretion can be an important energy source during some stages of pre-main sequence evolution is provided by the eruptions of FU Orionis objects. Radiation from the pre-main sequence star itself is a small fraction of the system luminosity, so it is relatively straightforward to infer the properties of the disk from direct observations. Various data, including the behavior of the light curve, the low resolution spectral energy distribution, and the structure of absorption features, are consistent with the idea that the luminosity observed in an FU Ori event is provided by viscous accretion onto a normal TTS.

The identification of accretion as an energy source in the less luminous TTS is more problematic, because the star contributes a large amount of optical flux and complicates the deconvolution of the energy distribution. Uncertainties in the UV extinction correction and the amount of stellar radiation reprocessed by the disk also make it difficult to determine directly the fraction of source luminosity which is derived by accretion.

Indirect arguments can still place useful constraints on the rate of accretion for broad classes of TTS. Simple boundary layer models suggest that the substantial veiling of the optical spectrum in the continuum TTS is consistent with an accretion rate of a few x 10−7 M⊙ yr−1. The lack of substantial veiling in most TTS indicates that accretion rates of M ∼ 10−8 M⊙ yr−1 are more typical of pre-main sequence stars.

I would like to thank L. Hartmann for helpful discussions and R. Hewett for making Figures 4 and 6. This paper was supported by the Scholarly Studies program of the Smithsonian Institution and by the National Aeronautics and Space Administration through grant NAGW-511.


Accretion Disk Accretion Rate Disk Model Central Star Tauri Star 
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© Springer-Verlag 1987

Authors and Affiliations

  • Scott J. Kenyon
    • 1
  1. 1.Harvard-Smithsonian Center for AstrophysicsCambridge

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