Dust in the inner regions of debris disks around A stars

The Astrophysical Journal (Impact Factor: 5.99). 02/2009; 691(2):1896. DOI: 10.1088/0004-637X/691/2/1896
Source: arXiv


We present infrared interferometric observations of the inner regions of two A-star debris disks, β Leo and ζ Lep,
using the FLUOR instrument at the CHARA interferometer on both short (30 m) and long (> 200 m) baselines.
For the target stars, the short-baseline visibilities are lower than expected for the stellar photosphere alone, while
those of a check star, δ Leo, are not. We interpret this visibility offset of a few percent as a near-infrared (NIR)
excess arising from dust grains which, due to the instrumental field of view, must be located within several AU of the central star. For β Leo, the NIR excess-producing grains are spatially distinct from the dust which produces
the previously known mid-infrared (MIR) excess. For ζ Lep, the NIR excess may be spatially associated with the MIR excess-producing material. We present simple geometric models which are consistent with the NIR and MIR excesses and show that for both objects, the NIR-producing material is most consistent with a thin ring of dust near the sublimation radius, with typical grain sizes smaller than the nominal radiation pressure blowout radius. Finally, we discuss possible origins of the NIR-emitting dust in the context of debris disk evolution models.

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Available from: Olivier Absil
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