# Asteroseismology of massive stars with the TESS mission: the runaway Beta Cep pulsator PHL 346 = HN Aqr

## TL;DR

This paper presents the first detailed asteroseismic analysis of the runaway Beta Cep pulsator PHL 346 using TESS data, revealing multiple oscillation modes and providing insights into its evolutionary status and interior structure.

## Contribution

It is the first to analyze a runaway Beta Cep pulsator with TESS, identifying numerous oscillation modes and constraining its age and internal structure.

## Key findings

- At least 34 oscillation modes detected, including g- and p-modes.
- The star's age is constrained to 23 ± 1 million years.
- Pulsation models suggest the star is older than initial models indicated.

## Abstract

We report an analysis of the first known Beta Cep pulsator observed by the TESS mission, the runaway star PHL 346 = HN Aqr. The star, previously known as a singly-periodic pulsator, has at least 34 oscillation modes excited, 12 of those in the g-mode domain and 22 p modes. Analysis of archival data implies that the amplitude and frequency of the dominant mode and the stellar radial velocity were variable over time. A binary nature would be inconsistent with the inferred ejection velocity from the Galactic disc of 420 km/s, which is too large to be survivable by a runaway binary system. A kinematic analysis of the star results in an age constraint (23 +- 1 Myr) that can be imposed on asteroseismic modelling and that can be used to remove degeneracies in the modelling process. Our attempts to match the excitation of the observed frequency spectrum resulted in pulsation models that were too young. Hence, asteroseismic studies of runaway pulsators can become vital not only in tracing the evolutionary history of such objects, but to understand the interior structure of massive stars in general. TESS is now opening up these stars for detailed asteroseismic investigation.