Spirals in protoplanetary disks from photon travel time

Abstract

Spiral structures are a common feature in scattered-light images of protoplanetary disks, and of great interest as possible tracers of the presence of planets. However, other mechanisms have been put foward to explain them, including self-gravity, disk-envelope interactions, and dead zone boundaries. These mechanisms explain many spirals very well, but are unable to easily account for very loosely wound spirals and single spiral arms. We study the effect of light travel time on the shape of a shadow cast by a clump orbiting close (within $\sim 1$au) of the central star, where there can be significant orbital motion during the light travel time from the clump to the outer disk and then to the sky plane. This delay in light rays reaching the sky plane gives rise to a variety of spiral- and arc-shaped shadows, which we describe with a general fitting formula for a flared, inclined disk.

arXiv commentAccepted for publication in A&A Letters. Videos available at dl.dropboxusercontent.com/u/3526708/spiralmovies.zip

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Cited by in corpus (14)

• Observations of Protoplanetary Disk Structures
• The Eccentric Cavity, Triple Rings, Two-Armed Spirals, and Double Clumps of the MWC 758 Disk
• Signatures of broken protoplanetary discs in scattered light and in sub-millimetre observations
• Spiral arms in the proto-planetary disc HD100453 detected with ALMA: evidence for binary-disc interaction and a vertical temperature gradient
• How Bright are Planet-Induced Spiral Arms in Scattered Light?
• Variable Outer Disk Shadowing Around the Dipper Star RX J1604.3-2130
• Variable dynamics in the inner disk of HD 135344B revealed with multi-epoch scattered light imaging
• Connecting the shadows: probing inner disk geometries using shadows in transitional disks
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• Planetary-like spirals caused by moving shadows in transition discs
• A "Rosetta Stone" for protoplanetary disks: The synergy of multi-wavelength observations
• Mapping of shadows cast on a protoplanetary disk by a close binary system
• Light Echoes of Protoplanetary Disks
• Gas and Dust Shadows in the TW Hydrae Disk