# Connecting the shadows: probing inner disk geometries using shadows in transitional disks

## TL;DR

This paper develops an analytic method to interpret shadow features in transitional disks, enabling the reconstruction of inner disk geometries and validating the approach with observations of HD100453.

## Contribution

The paper introduces a new analytic framework to determine inner disk orientation from shadow features, challenging previous assumptions and demonstrating consistency with interferometric data.

## Key findings

- Analytic equations relate shadow features to disk orientation.
- The method is validated with HD100453, showing consistency with observations.
- Supports the interpretation of shadows as indicators of misaligned inner disks.

## Abstract

Shadows in transitional disks are generally interpreted as signs of a misaligned inner disk. This disk is usually beyond the reach of current day high contrast imaging facilities. However, the location and morphology of the shadow features allow us to reconstruct the inner disk geometry. We derive analytic equations of the locations of the shadow features as a function of the orientation of the inner and outer disk and the height of the outer disk wall. In contrast to previous claims in the literature, we show that the position angle of the line connecting the shadows cannot be directly related to the position angle of the inner disk. We show how the analytic framework derived here can be applied to transitional disks with shadow features. We use estimates of the outer disk height to put constraints on the inner disk orientation. In contrast with the results from Long et al. (2017), we derive that for the disk surrounding HD100453 the analytic estimates and interferometric observations result in a consistent picture of the orientation of the inner disk. The elegant consistency in our analytic framework between observation and theory strongly support both the interpretation of the shadow features as coming from a misaligned inner disk as well as the diagnostic value of near infrared interferometry for inner disk geometry.