The Peculiar Debris Disk of HD 111520 as Resolved by the Gemini Planet Imager

TL;DR

This study used the Gemini Planet Imager to resolve the asymmetric debris disk around HD 111520, revealing a significant brightness asymmetry and polarization features that suggest azimuthal dust density variations.

Contribution

First resolved the debris disk around HD 111520 in both total and polarized light, revealing extreme asymmetry and detailed polarization properties.

Findings

2:1 brightness asymmetry between NW and SE extensions

Polarization fraction rises from 10% to 40% with distance from star

Tentative localized brightness and scale height enhancements at 40 AU

Abstract

Using the Gemini Planet Imager (GPI), we have resolved the circumstellar debris disk around HD 111520 at a projected range of ~30-100 AU in both total and polarized $H$-band intensity. The disk is seen edge-on at a position angle of ~165$^{\circ}$ along the spine of emission. A slight inclination or asymmetric warping are covariant and alters the interpretation of the observed disk emission. We employ 3 point spread function (PSF) subtraction methods to reduce the stellar glare and instrumental artifacts to confirm that there is a roughly 2:1 brightness asymmetry between the NW and SE extension. This specific feature makes HD 111520 the most extreme examples of asymmetric debris disks observed in scattered light among similar highly inclined systems, such as HD 15115 and HD 106906. We further identify a tentative localized brightness enhancement and scale height enhancement associated with the disk at ~40 AU away from the star on the SE extension. We also find that the fractional polarization rises from 10 to 40% from 0.5" to 0.8" from the star. The combination of large brightness asymmetry and symmetric polarization fraction leads us to believe that an azimuthal dust density variation is causing the observed asymmetry.