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.

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

References in corpus (9)

• Asymmetric features in the protoplanetary disk MWC758
• Magnetospheric accretion-ejection processes in the classical T Tauri star AA
• Direct Imaging of Fine Structures in Giant Planet Forming Regions of the Protoplanetary Disk around AB Aurigae
• CSI 2264: Probing the inner disks of AA Tau-like systems in NGC 2264
• CSI 2264: Characterizing Young Stars in NGC 2264 with Short-Duration, Periodic Flux Dips in their Light Curves
• HD100546 Multi-Epoch Scattered-Light Observations
• The HD 163296 Circumstellar Disk in Scattered Light: Evidence of Time-Variable Self-Shadowing
• Shadows and cavities in protoplanetary disks: HD163296, HD141569A, and HD150193A in polarized light
• Rossby wave instability does not require sharp resistivity gradients

Cited by in corpus (7)

• 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
• Variable dynamics in the inner disk of HD 135344B revealed with multi-epoch scattered light imaging
• Planetary-like spirals caused by moving shadows in transition discs
• A "Rosetta Stone" for protoplanetary disks: The synergy of multi-wavelength observations
• Gas and Dust Shadows in the TW Hydrae Disk
• Light Echoes of Protoplanetary Disks