Dimming and co absorption toward the AA Tau protoplanetary disk: An infalling flow caused by disk instability?
- Division of Physics, Mathematics and Astronomy, MC 249-17, California Institute of Technology, Pasadena, CA 91125 (United States)
- Division of Geological and Planetary Sciences, MC 150-21, California Institute of Technology, Pasadena, CA 91125 (United States)
- National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
AA Tau, a classical T Tauri star in the Taurus cloud, has been the subject of intensive photometric monitoring for more than two decades due to its quasi-cyclic variation in optical brightness. Beginning in 2011, AA Tau showed another peculiar variation—its median optical though near-IR flux dimmed significantly, a drop consistent with a 4-mag increase in visual extinction. It has stayed in the faint state since. Here we present 4.7 μm CO rovibrational spectra of AA Tau over eight epochs, covering an 11 yr time span, that reveal enhanced {sup 12}CO and {sup 13}CO absorption features in the J{sub low} ≤ 13 transitions after the dimming. These newly appeared absorptions require molecular gas along the line of sight with T ∼ 500 K and a column density of log (N {sub {sup 1}{sup 2}CO}) ∼18.5 cm{sup −2}, with line centers that show a constant 6 km s{sup −1} redshift. The properties of the molecular gas confirm an origin in the circumstellar material. We suggest that the dimming and absorption are caused by gas and dust lifted to large heights by a magnetic buoyancy instability. This material is now propagating inward, and on reaching the star within a few years will be observed as an accretion outburst.
- OSTI ID:
- 22883174
- Journal Information:
- Astrophysical Journal, Vol. 805, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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