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Temperature and Observables of Tilted Classical Be Star Disks

Presentation #233.01 in the session Circumstellar Disks.

Published onJul 01, 2023
Temperature and Observables of Tilted Classical Be Star Disks

Recent simulations of Classical Be stars have shown that a misaligned binary companion can tilt and warp the disk away from the equatorial plane of the primary star. While the dynamics of tilted disks have been studied, predictions of their temperature structure and observables compared to non-tilted disks have not been explored. In this study, we compute 128 radiative transfer models of classical Be star disks across four spectral types: B0, B2, B5 and B8, tilting the disk by 0, 10, 20, or 40 degrees, while varying the disk density and stellar rotation rate between high and average values. We find tilting the disk minimally affects the average disk temperature, however tilting does create a temperature asymmetry in the disk cross-section, with half of the disk becoming hotter, and half becoming cooler than the non-tilted case. We also explore the changes tilting can cause to the V-band magnitude, Hα emission line, and polarization signature of the disk. We find the changes in observables due to tilting can be substantial, but are entirely dependent on the relative orientation between the tilt of the disk and the observer. The observables that can distinguish tilting from an alternative change in disk density or geometry are the Hα line profile, where it can transition between being singly and doubly-peaked, and the polarization position angle, whose value is determined by the projection of the polarization vector on the sky. The models presented here represent a key step towards modelling disks with more complex geometries such as warping and tearing.

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