Discovery of a Two-Armed Spiral Structure in the Gapped Disk in HD 100453

TL;DR

This paper reports the discovery of a two-armed spiral structure and a potential planet-cleared gap in the disk around HD 100453, using high-resolution imaging, providing insights into disk morphology and planet formation.

Contribution

First direct imaging of a two-armed spiral and a gap in the disk of HD 100453, suggesting planet formation activity and disk-planet interactions.

Findings

Discovery of a two-armed spiral structure extending to 42 AU.

Detection of a gap likely cleared by forming planets.

Observation of a companion star with an estimated orbital period of 850 years.

Abstract

We present VLT/SPHERE adaptive optics imaging in Y$-$, J$-$, H$-$, and K-bands of the HD 100453 system and the discovery of a two-armed spiral structure in a disk extending to 0.37" ($\sim$42 AU) from the star, with highly symmetric arms to the Northeast and Southwest. Inside of the spiral arms, we resolve a ring of emission from 0.18"-0.25" ($\sim$21-29 AU). By assuming that the ring is intrinsically circular we estimate an inclination of $\sim$34$^{o}$ from face-on. We detect dark crescents on opposite sides (NW and SE) which begin at 0.18" and continue to radii smaller than our inner working angle of 0.15", which we interpret as the signature of a gap at $\lesssim$21 AU that has likely been cleared by forming planets. We also detect the $\sim$120 AU companion HD 100453 B, and by comparing our data to 2003 HST/ACS and VLT/NACO images we estimate an orbital period of $\sim$850 yr. We discuss what implications the discovery of the spiral arms and finer structures of the disk may have on our understanding of the possible planetary system in HD 100453, and how the morphology of this disk compares to other related objects.