Herbig Stars' Near-Infrared Excess: An Origin in the Protostellar Disk's Magnetically-Supported Atmosphere
| Autor: | Turner, N. J., Benisty, M., Dullemond, C. P., Hirose, S. |
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| Rok vydání: | 2013 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1088/0004-637X/780/1/42 |
| Popis: | 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. Comment: 23 pages, 8 figures. Grain settling discussed in new sec. 8.3. In press at ApJ |
| Databáze: | arXiv |
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