Bright Localized Near-Infrared Emission at 1-4 AU in the AB Aurigae Disk Revealed by IOTA Closure Phases

Abstract

We report on the detection of localized off-center emission at 1-4 AU in the circumstellar environment of the young stellar object AB Aurigae. We used closure phase measurements in the near-infrared made at the long baseline interferometer IOTA, the first obtained on a young stellar object using this technique. When probing sub-AU scales, all closure phases are close to zero degrees, as expected given the previously-determined size of the AB Aurigae inner dust disk. However, a clear closure phase signal of -3.5 +/- 0.5 degrees is detected on one triangle containing relatively short baselines, requiring a high degree of non-point symmetry from emission at larger (AU-sized) scales in the disk. We have not identified any alternative explanation for these closure phase results and demonstrate that a ``disk hot spot'' model can fit our data. We speculate that such asymmetric near-infrared emission detected might arise as a result of localized viscous heating due to a gravitational instability in the AB Aurigae disk, or to the presence of a close stellar companion or accreting sub-stellar object.

arXiv commentAccepted by Astrophysical Journal Letters

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• Imaging the heart of astrophysical objects with optical long-baseline interferometry
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• Exploring intermediate (5-40AU) scales around AB Aurigae with the Palomar Fiber Nuller
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• LBT search for companions and sub-structures in the (pre)transitional disk of AB Aurigae
• 10 $\mu$m interferometry of disks around young stars
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