Discovery of new magnetic δ Scuti stars and the impact of magnetism on pulsation excitation

¹ LIRA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, 92190 Meudon, France
² School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
³ DTU Space, Technical University of Denmark, Elektrovej 327, Kgs. Lyngby 2800, Denmark
⁴ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, F-91191 Gif-sur-Yvette, France

^⋆ Corresponding author: keegan.thomson-paressant@obspm.fr

Received: 5 August 2025
Accepted: 16 October 2025

Abstract

Context. At this time, the list of known magnetic δ Scuti stars is extremely limited, with only a select number of well-studied examples.

Aims. We seek to expand this list, by retrieving targets from a variety of sources and demonstrating that they present simultaneously a surface magnetic field signature and δ Scuti pulsations.

Methods. We obtained archival and new spectropolarimetric datasets for a variety of known δ Scuti stars and analysed them using the least squares deconvolution method to generate mean Stokes I and V profiles for each target, from which we can determine longitudinal magnetic field measurements. Additionally, we assessed photometric data from the TESS satellite to discern frequency peaks consistent with δ Scuti pulsations in known magnetic stars, and to identify magnetic candidates via rotational modulation.

Results. We present a compiled list of all the confirmed magnetic δ Scuti stars discovered to date, containing 13 stars. The majority of this sample lies outside the usual δ Scuti instability strip in the Hertzsprung-Russell diagram, though we do not observe any specific correlations between magnetic field strength and various stellar parameters. This indicates that strong global magnetic fields play a fundamental role in shaping interior structure and processes. Magnetic fields thus must be included in realistic stellar models in order to more accurately predict structure and evolution.

Conclusions. This work constitutes the largest database to date of strongly magnetic δ Scuti stars, one that will continue to grow over time with subsequent studies.