THE BIMODALITY OF ACCRETION IN T TAURI STARS AND BROWN DWARFS

Journal Article · Sun Sep 20 00:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/703/1/922· OSTI ID:21371958

Vorobyov, E I ^[1]; Basu, Shantanu ^[2]

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1. Institute for Computational Astrophysics, Saint Mary's University, Halifax, B3H 3C3 (Canada)
2. Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7 (Canada)

We present numerical solutions of the collapse of prestellar cores that lead to the formation and evolution of circumstellar disks. The disk evolution is then followed for up to three million years. A variety of models of different initial masses and rotation rates allow us to study disk accretion around brown dwarfs and low-mass T Tauri stars (TTSs), with central object mass M{sub *} < 0.2 M{sub sun}, as well as intermediate- and upper-mass TTSs (0.2 M{sub sun} < M{sub *} < 3.0 M{sub sun}). Our models include self-gravity and allow for nonaxisymmetric motions. In addition to the self-consistently generated gravitational torques, we introduce an effective turbulent alpha-viscosity with alpha = 0.01, which allows us particularly to model accretion in the low-mass regime where disk self-gravity is diminishing. A range of models with observationally motivated values of the initial ratio of rotational-to-gravitational energy yield a correlation between mass accretion rate M-dot and M{sub *} that is relatively steep, as observed. Additionally, our modeling reveals evidence for a bimodality in the M-dot - M{sub *} correlation, with a steeper slope at lower masses and a shallower slope at intermediate and upper masses, as also implied by observations. Furthermore, we show that the neglect of disk self-gravity leads to a much steeper M-dot - M{sub *} relation for intermediate- and upper-mass TTSs. This demonstrates that an accurate treatment of global self-gravity is essential to understanding observations of circumstellar disks.

• OSTI ID: 21371958
• Journal Information: Astrophysical Journal, Vol. 703, Issue 1; Other Information: DOI: 10.1088/0004-637X/703/1/922; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
CORRELATIONS
ENERGY YIELD
GRAVITATION
HYDRODYNAMICS
MASS
NUMERICAL SOLUTION
ROTATION
SIMULATION
STAR EVOLUTION
T TAURI STARS
TORQUE
BINARY STARS
ERUPTIVE VARIABLE STARS
EVOLUTION
FLUID MECHANICS
MATHEMATICAL SOLUTIONS
MECHANICS
MOTION
STARS
VARIABLE STARS