# Combined asteroseismology, spectroscopy, and astrometry of the CoRoT B2V target HD 170580

## TL;DR

This study combines asteroseismology, spectroscopy, and astrometry to probe the internal structure of the massive B2V star HD 170580, revealing insights into its rotation, evolution, and the need for improved stellar models.

## Contribution

It provides a comprehensive analysis of HD 170580 using multiple observational methods and highlights the necessity of including atomic diffusion in stellar models for better accuracy.

## Key findings

- Detected 42 pulsation frequencies, including rotationally split triplets and a quintuplet.
- Estimated the star's mass at 8 solar masses near core-hydrogen exhaustion.
- Identified the star as a slow rotator with a rotation period between 73 and 98 days.

## Abstract

Space asteroseismology reveals that stellar structure and evolution models of intermediate- and high-mass stars are in need of improvement in terms of angular momentum and chemical element transport. We aim to probe the interior structure of a hot massive star in the core-hydrogen burning phase of its evolution. We analyse CoRoT space photometry, Gaia DR2 space astrometry, and high-resolution high signal-to-noise HERMES and HARPS time-series spectroscopy of the slowly rotating B2V star HD 170580. From the time-series spectroscopy we derive $vsini=4\pm 2\,$km\,s$^{-1}$, where the uncertainty results from the complex pulsational line-profile variability. We detect 42 frequencies with amplitude above 5$\sigma$. Among these we identify 5 rotationally split triplets and 1 quintuplet. Asteroseismic modelling based on CoRoT, Gaia DR2 and spectroscopic data leads to a star of 8M$_\odot$ near core-hydrogen exhaustion and an extended overshoot zone. The detected low-order pressure-mode frequencies cannot be fit within the uncertainties of the CoRoT data by models without atomic diffusion. Irrespective of this limitation, the low-order gravity modes reveal HD 170580 to be a slow rotator with an average rotation period between 73 and 98 d and a hint of small differential rotation. Future Gaia DR3 data taking into account the multiplicity of the star, along with long-term TESS photometry would allow to put better observational constraints on the asteroseismic models of this blue evolved massive star. Improved modelling with atomic diffusion, including radiative levitation, is needed to achieve compliance with the low helium surface abundance of the star. This poses immense computational challenges but is required to derive the interior rotation and mixing profiles of this star.