Imaging an 80 AU Radius Dust Ring Around the F5V Star HD 157587

TL;DR

This study uses near-infrared polarimetric imaging to reveal an 80 AU dust ring around HD 157587, analyzing its structure, asymmetries, and possible stellar offset, contributing new detailed disk modeling.

Contribution

First detailed polarimetric imaging of HD 157587's debris disk, constraining its geometry, asymmetries, and potential stellar offset with novel disk modeling approaches.

Findings

Disk inclination ~70 degrees

Stellar offset of 1.5±0.6 AU along the major axis

Detection of three point sources likely background objects

Abstract

We present $H$-band near-infrared polarimetric imaging observations of the F5V star HD~157587 obtained with the Gemini Planet Imager (GPI) that reveal the debris disk as a bright ring structure at a separation of $\sim$80$-$100~AU. The new GPI data complement recent HST/STIS observations that show the disk extending out to over 500~AU. The GPI image displays a strong asymmetry along the projected minor axis as well as a fainter asymmetry along the projected major axis. We associate the minor and major axis asymmetries with polarized forward scattering and a possible stellocentric offset, respectively. To constrain the disk geometry we fit two separate disk models to the polarized image, each using a different scattering phase function. Both models favor a disk inclination of $\sim 70\degr$ and a $1.5\pm0.6$ AU stellar offset in the plane of the sky along the projected major axis of the disk. We find that the stellar offset in the disk plane, perpendicular to the projected major axis is degenerate with the form of the scattering phase function and remains poorly constrained. The disk is not recovered in total intensity due in part to strong adaptive optics residuals, but we recover three point sources. Considering the system's proximity to the galactic plane and the point sources' positions relative to the disk, we consider it likely that they are background objects and unrelated to the disk's offset from the star.