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arXiv · 1309.0762

Herbig Stars' Near-Infrared Excess: An Origin in the Protostellar Disk's Magnetically-Supported Atmosphere

N. J. Turner·M. Benisty·C. P. Dullemond·S. Hirose
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Abstract

Young stars with masses 2-8 Suns, called the Herbig Ae and Be stars, often show a near-infrared excess too large to explain with a hydrostatically-supported circumstellar disk of gas and dust. At the same time the accretion flow carrying the circumstellar gas to the star is thought to be driven by magneto-rotational turbulence, which according to numerical MHD modeling yields an extended low-density atmosphere supported by the magnetic fields. We demonstrate that the base of the atmosphere can be optically-thick to the starlight and that the parts lying near 1 AU are tall enough to double the fraction of the stellar luminosity reprocessed into the near-infrared. We generate synthetic spectral energy distributions (SEDs) using Monte Carlo radiative transfer calculations with opacities for sub-micron silicate and carbonaceous grains. The synthetic SEDs closely follow the median Herbig SED constructed recently by Mulders and Dominik, and in particular match the large near-infrared flux, provided the grains have a mass fraction close to interstellar near the disk's inner rim.

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N. J. Turner, M. Benisty, C. P. Dullemond, S. Hirose. 2013-10-27. Herbig Stars' Near-Infrared Excess: An Origin in the Protostellar Disk's Magnetically-Supported Atmosphere. https://doi.org/10.1088/0004-637x%2F780%2F1%2F42

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