Determination of the inclination of the multi-planet hosting star HR8799 using asteroseismology

TL;DR

This study uses asteroseismology of HR8799 to independently determine the star's inclination, providing insights into the system's geometry and aiding exoplanet characterization.

Contribution

It demonstrates how high-resolution spectroscopic observations and mode identification can constrain the inclination of a multi-planet host star.

Findings

Main frequency in radial velocity data is 1.9875 d$^{-1}$.

Frequency corresponds to a prograde $ ext{l}=1$ mode.

Inclination of the star is constrained to be greater than approximately 40 degrees.

Abstract

Direct imaging of the HR8799 system was a major achievement in the study of exoplanets. HR8799 is a $\gamma$\,Doradus variable and asteroseismology can provide an independent constraint on the inclination. Using 650 high signal-to-noise, high resolution, full visual wavelength spectroscopic observations obtained over two weeks at Observatoire de Haute Provence (OHP) with the SOPHIE spectrograph we find that the main frequency in the radial velocity data is 1.9875 d$^{-1}$. This frequency corresponds to the main frequency as found in previous photometric observations. Using the FAMIAS software to identify the pulsation modes, we find this frequency is a prograde $\ell$=1 sectoral mode and obtain the constraint that inclination $i\gtrsim$40$^{\circ}$.