2010ApJ...717...93A

The Chandra Orion Ultradeep Project observed hundreds of young, low-mass stars undergoing highly energetic X-ray flare events. The 32 most powerful cases have been previously modeled with the result that the magnetic structures responsible for these flares can be many stellar radii in extent. In this paper, we model the observed spectral energy distributions (SEDs) of these 32 stars in order to determine, in detail for each star, whether there is circumstellar disk material situated in sufficient proximity to the stellar surface for interaction with the large magnetic loops inferred from the observed X-ray flares. Our SEDs span the wavelength range 0.3-8 µm (plus 24 µm for some stars), allowing us to constrain the presence of dusty circumstellar material out to ≳10 AU from the stellar surface in most cases. For 24 of the 32 stars in our sample the available data are sufficient to constrain the location of the inner edge of the dusty disks. Six of these (25%) have SEDs consistent with inner disks within reach of the observed magnetic loops. Another four stars may have gas disks interior to the dust disk and extending within reach of the magnetic loops, but we cannot confirm this with the available data. The remaining 14 stars (58%) appear to have no significant disk material within reach of the large flaring loops. Thus, up to ∼40% of the sample stars exhibit energetic X-ray flares that possibly arise from a magnetic star-disk interaction, and the remainder are evidently associated with extremely large, free-standing magnetic loops anchored only to the stellar surface.