Abstract
Abstract We present new 0.6–4 μm imaging of the SR 21 transition disk from Keck/NIRC2 and Magellan/MagAO. The protoplanetary disk around SR 21 has a large (∼30–40 au) clearing first inferred from its spectral energy distribution and later detected in submillimeter imaging. Both the gas and small dust grains are known to have a different morphology, with an inner truncation in CO at ∼7 au, and micron-sized dust detected within the millimeter clearing. Previous near-infrared imaging could not distinguish between an inner dust disk with a truncation at ∼7 au or one that extended to the sublimation radius. The imaging data presented here require an inner dust disk radius of a few au, and complex structure such as a warp or spiral. We present a parametric warped disk model that can reproduce the observations. Reconciling the images with the spectral energy distribution gathered from the literature suggests grain growth to ≳2–5 μm within the submillimeter clearing. The complex disk structure and possible grain growth can be connected to dynamical shaping by a giant-planet-mass companion, a scenario supported by previous observational and theoretical studies.
Highlights
Protoplanetary disks - the circumstellar disks of dust and gas that remain after star formation - are understood to be the sites of planet formation
The protoplanetary disk around SR 21 has a large (∼ 30 − 40 AU) clearing first inferred from its spectral energy distribution and later detected in sub-millimeter imaging
Previous near-infrared imaging could not distinguish between an inner dust disk with a truncation at ∼ 7 AU or one that extended to the sublimation radius
Summary
Protoplanetary disks - the circumstellar disks of dust and gas that remain after star formation - are understood to be the sites of planet formation. We present infrared NRM and visible filled-aperture observations of the transition disk around SR 21.2 SR 21 is a G3 star in Ophiuchus, at a distance of 138 pc (Gaia Collaboration et al 2016).. Imaging at 8.8 μm and 11.6 μm yield characteristic mid-IR sizes of 67 and 92 mas, respectively, corresponding to 9 and 13 AU at 138 pc (Eisner et al 2009) These data suggest the presence of a compact, warm companion - possibly circumplanetary material - at a disk gap edge at approximately 6 AU (Eisner et al 2009). The near-infrared and visible light observations of SR 21 presented here probe tighter separations than previous direct imaging studies They resolve the location of the companion posited in Eisner et al (2009) at wavelengths where it is predicted to be relatively bright.
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