Introducing CAFein, a New Computational Tool for Stellar Pulsations and Dynamic Tides

TL;DR

CAFein is a new computational tool that models stellar pulsations and dynamic tides in close binary systems, enabling detailed analysis of non-adiabatic oscillations and tidal effects on stellar and orbital evolution.

Contribution

It extends the Riccati method to study dynamic tides in close binaries and demonstrates capabilities in both adiabatic and non-adiabatic stellar pulsation analysis.

Findings

Successfully reproduces eigenfrequencies of stellar models.

Identifies unstable modes in the $eta$ Cephei/SPB region.

Analyzes tidal effects on orbital and spin evolution.

Abstract

Here we present CAFein, a new computational tool for investigating radiative dissipation of dynamic tides in close binaries and of non-adiabatic, non-radial stellar oscillations in isolated stars in the linear regime. For the latter, CAFein computes the non-adiabatic eigenfrequencies and eigenfunctions of detailed stellar models. The code is based on the so-called Riccati method, a numerical algorithm that has been successfully applied to a variety of stellar pulsators, and which doesn't suffer of the major drawbacks of commonly used shooting and relaxation schemes. Here we present an extension of the Riccati method to investigate dynamic tides in close binaries. We demonstrate CAFein's capabilities as a stellar pulsation code both in the adiabatic and non-adiabatic regime, by reproducing previously published eigenfrequencies of a polytrope, and by successfully identifying the unstable modes of a stellar model in the $\beta$ Cephei/SPB region of the Hertzsprung-Russell diagram. Finally, we verify CAFein's behavior in the dynamic tides regime by investigating the effects of dynamic tides on the eigenfunctions and orbital and spin evolution of massive Main Sequence stars in eccentric binaries, and of hot Jupiter host stars. The plethora of asteroseismic data provided by the NASA's Kepler satellite, some of which include the direct detection of tidally excited stellar oscillations, make CAFein quite timely. Furthermore, the increasing number of observed short-period detached double white dwarfs (WD) and the observed orbital decay in the tightest of such binaries open up a new possibility of investigating WD interiors through the effects of tides on their orbital evolution