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We present Atacama Large Millimeter/submillimeter Array (ALMA) observationsin the dust continuum (690 GHz, 0.45 mm) and 12CO J=6-5 spectral line emission,of the transitional disks surrounding the stars SAO 206462 and SR 21. TheseALMA observations resolve the dust-depleted disk cavities and extended gaseousdisks, revealing large-scale asymmetries in the dust emission of both disks. Wemodeled these disks structures with a ring and an azimuthal gaussian, where theazimuthal gaussian is motivated by the steady-state vortex solution from Lyra &Lin (2013). Compared to recent observations of HD 142527, Oph IRS 48, and LkHa330, these are low-contrast (< 2) asymmetries. Nevertheless, a ring alone isnot a good fit, and the addition of a vortex prescription describes these datamuch better. The asymmetric component encompasses 15% and 28% of the total diskemission in SAO 206462 and SR 21 respectively, which corresponds to a lowerlimit of 2 MJup of material within the asymmetry for both disks. Although thecontrast in the dust asymmetry is low, we find that the turbulent velocityinside it must be large (~20% of the sound speed) in order to drive theseazimuthally wide and radially narrow vortex-like structures. We obtainresiduals from the ring and vortex fitting that are still significant, tracingnon-axisymmetric emission in both disks. We compared these submillimeterobservations with recently published H-band scattered light observations. ForSR 21 the scattered light emission is distributed quite differently from thesubmillimeter continuum emission, while for SAO 206462 the submillimeterresiduals are suggestive of spiral-like structure similar to the near-IRemission.

Large-Scale Asymmetries in the Transitional Disks of SAO 206462 and SR 21