Gautam Paul, Coralie Neiner, Claude Catala, Jonathan Labadie-Bartz

delta Scuti stars are pulsating stars constituting the delta Scuti instability strip in the HR diagram, which consists of A and F stars of various evolutionary stages. They are in the transition region between high-mass hot stars and low-mass solar-like stars, making it essential to understand their magnetic properties to understand magnetism across the HR diagram. Also, discovering magnetic delta Scuti stars allows for magneto-asteroseismology, which can determine the internal rotation profile, internal magnetic field strength, and the efficiency of mixing and transport processes more accurately than classical asteroseismology. To date, magnetic fields have been detected at the surface of 13 delta Scuti stars. However, the overall incidence rate of magnetism in these stars remains unknown. Fossil magnetic fields are detected in 10\% of OBA stars. In this work, we investigated the incidence rate of surface magnetic fields among delta Scuti stars using photometric data from the CoRoT space mission. We analyzed long-duration (~5-month) light curves of ~1750 delta Scuti stars to search for pulsations and rotational modulation - a photometric signature that indicates chemical or temperature spots at the stellar surface, usually caused by magnetic fields. We have identified 147 rotational variables, which we designate as magnetic candidates, potentially drastically increasing the known population of magnetic delta Scuti stars, suggesting an incidence rate of fossil magnetic fields in delta Scuti stars similar to the incidence rate in OBA stars in general. Our analysis has also revealed a few delta Scuti - gamma Dor hybrid stars and four binary stars in the sample. We have determined rotation periods and projected rotation velocities of the magnetic candidates to select suitable targets for follow-up spectropolarimetric observations to confirm and characterize their magnetic fields.