# Revisiting the pulsational characteristics of the exoplanet host star $\beta$ Pictoris

## TL;DR

This study revisits the pulsational properties of the exoplanet host star beta Pictoris using multi-passband photometry and spectropolarimetry, identifying pulsation modes and constraining stellar parameters with asteroseismology.

## Contribution

It provides a detailed mode identification and stellar parameter estimation for beta Pictoris, incorporating multi-instrument data and 2D rotating models, and confirms the star's non-magnetic nature.

## Key findings

- Identified 15 pulsation frequencies between 34 and 55 c/d.
- Mode identification includes 3 l=1, 6 l=2, and 6 l=3 modes.
- Determined stellar parameters: radius ~1.5 R_sun, mass ~1.8 M_sun, rotation rate 27% of break-up velocity.

## Abstract

Exoplanet properties crucially depend on their host stars' parameters. In case the exoplanet host star shows pulsations, asteroseismology can be used for an improved description of the stellar parameters. We aim to revisit the pulsational properties of beta Pic and identify its pulsation modes from normalised amplitudes in five different passbands. We also investigate the potential presence of a magnetic field. We conduct a frequency analysis using three seasons of BRITE-Constellation observations in the BRITE blue and red filters, the ~620-day long bRing light curve and the nearly 8-year long SMEI photometric time series. We calculate normalised amplitudes using all passbands including previously published values obtained from ASTEP observations. We investigate the magnetic properties of beta Pic using spectropolarimetric observations conducted with the HARPSpol instrument. Using 2D rotating models, we fit the normalised amplitudes and frequencies through Monte Carlo Markov Chains. We identify 15 pulsation frequencies in the range from 34 to 55c/d, where two display clear amplitude variability. We use the normalised amplitudes in up to five passbands to identify the modes as three l = 1, six l = 2 and six l = 3 modes. beta Pic is shown to be non-magnetic with an upper limit of the possible undetected dipolar field of 300G. Multiple fits to the frequencies and normalised amplitudes are obtained including one with a near equator-on inclination for beta Pic, which corresponds to our expectations based on the orbital inclination of beta Pic b and the orientation of the circumstellar disk. This solution leads to a rotation rate of 27% of the Keplerian break-up velocity, a radius of 1.497+-0.025Rsun, and a mass of 1.797+-0.035Msun. The ~2% errors in radius and mass do not account for uncertainties in the models and a potentially erroneous mode-identification.