Synthetic Spectra of Rotating Stars

TL;DR

This paper introduces PARS, a novel integration scheme for generating synthetic spectra of rapidly rotating stars with oblate shapes and temperature variations, enabling detailed spectral analysis of such stars.

Contribution

The paper presents PARS, a new method for integrating stellar spectra over oblate, rotating star models, incorporating advanced numerical techniques and temperature calculations up to near-Keplerian rotation.

Findings

Accurate synthetic spectra for stars rotating up to 99.9% of Keplerian limit.

The scheme enables creation of color-magnitude diagrams and planetary transit curves.

Provides a computational tool accessible via GitHub.

Abstract

Many early-type stars have oblate surfaces, spatial temperature variations, and spectral line broadening that indicate large rotational velocities. Rotation ought to have a significant effect on the full spectra of such stars. To infer structural and life history parameters from their spectra, one must integrate specific intensity over the two-dimensional surfaces of corresponding stellar models. Toward this end, we offer PARS (Paint the Atmospheres of Rotating Stars) -- an integration scheme based on models that incorporate solid body rotation, Roche mass distribution, and collinearity of gravity and energy flux (https://github.com/mlipatov/paint_atmospheres). The scheme features a closed-form expression for the azimuthal integral, a high-order numerical approximation of the longitudinal integral, and a precise calculation of surface effective temperature at rotation rates up to 99.9% of Keplerian limit. Extensions of the scheme include synthetic color-magnitude diagrams and planetary transit curves.