# The shadow knows: using shadows to investigate the structure of the pretransitional disk of HD 100453

## TL;DR

This study uses polarized imaging and radiative transfer modeling to analyze the structure of HD 100453's pretransitional disk, revealing an inner gap, spiral arms, and shadow features caused by disk misalignment.

## Contribution

The paper combines high-resolution polarized imaging with radiative transfer modeling to characterize the disk's structure and inclination, providing new insights into disk misalignment and shadow features.

## Key findings

- Inner disk gap of 9-18 au identified
- Disk inclination difference of 45 degrees measured
- Outer disk inclination estimated at 25 degrees

## Abstract

We present GPI polarized intensity imagery of HD 100453 in Y-, J-, and K1 bands which reveals an inner gap ($9 - 18$ au), an outer disk ($18-39$ au) with two prominent spiral arms, and two azimuthally-localized dark features also present in SPHERE total intensity images (Wagner 2015). SED fitting further suggests the radial gap extends to $1$ au. The narrow, wedge-like shape of the dark features appears similar to predictions of shadows cast by a inner disk which is misaligned with respect to the outer disk. Using the Monte Carlo radiative transfer code HOCHUNCK3D (Whitney 2013), we construct a model of the disk which allows us to determine its physical properties in more detail. From the angular separation of the features we measure the difference in inclination between the disks 45$^{\circ}$, and their major axes, PA = 140$^{\circ}$ east of north for the outer disk and 100$^{\circ}$for the inner disk. We find an outer disk inclination of $25 \pm 10^{\circ}$ from face-on in broad agreement with the Wagner 2015 measurement of 34$^{\circ}$. SPHERE data in J- and H-bands indicate a reddish disk which points to HD 100453 evolving into a young debris disk.