期刊
ASTRONOMY & ASTROPHYSICS
卷 584, 期 -, 页码 -出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201425583
关键词
circumstellar matter; stars: pre-main sequence; stars: variables: T Tauri, Herbig Ae/Be; stars: individual: AA Tau; X-rays: stars; ultraviolet: stars
资金
- DLR [50 OR 1307]
- Nancy Grace Roman Fellowship
- NASA/Chandra Award [GO4-15009X]
- NASA [NAS8-03060, NAS5-26555]
- ESA Member States
- NASA Office of Space Science [NAG5-7584]
AA Tau is a well-studied, nearby classical T Tauri star, which is viewed almost edge-on. A warp in its inner disk periodically eclipses the central star, causing a clear modulation of its optical light curve. The system underwent a major dimming event beginning in 2011 caused by an extra absorber, which is most likely associated with additional disk material in the line of sight toward the central source. We present new XMM-Newton X-ray, Hubble Space Telescope FUV, and ground-based optical and near-infrared data of the system obtained in 2013 during the long-lasting dim phase. The line width decrease of the fluorescent H-2 disk emission shows that the extra absorber is located at r > 1 au. Comparison of X-ray absorption (NH) with dust extinction (A(V)), as derived from measurements obtained one inner disk orbit (eight days) after the X-ray measurement, indicates that the gas-to-dust ratio as probed by the N-H to AV ratio of the extra absorber is compatible with the ISM ratio. Combining both results suggests that the extra absorber, i.e., material at r > 1 au, has no significant gas excess in contrast to the elevated gas-to-dust ratio previously derived for material in the inner region (<= 0.1 au).
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