PIMMS: Pulsation-Informed Magnetic Mapping of Stars with Zeeman-Doppler imaging

I. Formalism and numerical tests

¹ LIRA, Observatoire de Paris, PSL University, CNRS, Sorbonne Université, Université Paris Cité, CY Cergy University, 5 place Jules Janssen, 92195 Meudon, France
² Tartu Observatory, University of Tartu, Observatooriumi 1, Tõravere 61602, Estonia

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 10 June 2025
Accepted: 6 October 2026

Abstract

Context. Magneto-asteroseismology is a novel technique allowing for more precise determinations of internal properties of magnetic pulsating stars, but it requires an accurate characterisation of the surface magnetic field that was not previously possible with Zeeman-Doppler imaging (ZDI) due to the time-dependent surface velocity of pulsating stars.

Aims. We aim to develop a new version of ZDI, which creates an additional surface velocity map that includes the time-dependent velocities of surface elements due to pulsations.

Methods. We present a new code, Pulsation-Informed Magnetic Mapping of Stars (PIMMS), which uses a surface-integrated line profile model that accounts for the additional Doppler shifts of local lines caused by pulsations. It is thus possible to fit this model to spectropolarimetric observations, reconstructing maps of the surface brightness, magnetic field, and the velocity field due to the combination of pulsation and rotation. In this paper, we present and explain how we tested PIMMS extensively, to understand its limitations and data requirements.

Results. We find that PIMMS can accurately reproduce the magnetic fields and brightness distributions of realistic models of pulsating hot stars. The required number of observations is higher than that required for ZDI of a non-pulsating star due to the additional velocity map that must be disentangled from surface brightness variations. PIMMS is now ready to be applied to real stars.