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The latest News in the Physics of A&F Stars:‬‭ Insights from Kepler and‬ ‭ TESS

Antoci, Victoria

Publisher
Zenodo
DOI
10.5281/zenodo.17434694
Repository
zenodo.org
Language
en

Abstract

A&F-type stars occupy a critical region‬‭ of the Hertzsprung–Russell‬ diagram where several key physical processes converge. This region overlaps‬ with the classical instability strip, where many stars exhibit pulsations, and‬ marks a structural transition from deep, efficient convective envelopes to‬ shallower, less effective ones. For slow rotators, this transition significantly‬ limits envelope mixing, with major consequences for chemical transport,‬ surface abundances, the generation of magnetic fields, and pulsational‬ properties. The presence of moderate to rapid rotation or fossil magnetic fields‬‭ introduces further complexity, modifying internal mixing, angular momentum‬ transport and stellar structure in ways that continue to challenge both‬ theoretical models and observational constraints. In this talk, I will review‬ recent progress in our understanding of A&F-type stars, with a particular focus‬ on pulsating classes observed with Kepler and TESS.‬

Full text

Victoria Antoci DTU Space The latest News in the Physics of A&F Stars: Insights from Kepler and TESS Victoria Antoci DTU Space The latest News in the Physics of A&F Stars: Insights from Kepler and TESS A VERY VERY BIASED VIEW! A&F stars in the broader picture… ★Intermediate-mass (1.3-3 Msun)! ★Teff: 6700 K - 10 000 K! ★near and on the main sequence (MS). Radial ! fundamental p-modes g-modes r-modes radial order ng radial order np Rotation many ! hybrids Only 1 or 2 ! known hybrids 2 or 3 hybrid candidate Frequency Amplitude Cantiello & Braithwaite 2019 ➡ “[Fingering convection] is an unavoidable consequence of the diffusion-induced inverse μ-gradient.” (Deal et al. 2016)! ➡ Models computed with atomic diffusion (including radiative acceleration effects) and a mild mixing below the convective envelope, show episodic convection in the Z bump (Theado et al. 2012). Convection Mixing Processes Convection Rotation Atomic diffusion Magnetic fields Credit: Royer 2009 Rotation & Angular momentum transport Mixing Processes Convection Rotation Atomic diffusion Magnetic fields Monnier et al. 2007 Teffeq = 6850 ± 120 K Teffpole = 8710 ± 160 K Slow rotation & shallow convection Diffusion of heavy elements (Atomic) Diffusion Light Elements Heavy elements gravitational settling radiative ! levitation HI, HeI convection zone radiative Mixing processes Mixing Processes Convection Rotation Atomic diffusion Magnetic fields Magnetic fields Strong, large-scale, stable magnetic fields in about 10% of A&F stars attributed to fossil fields! Kochuchukov et al. 2015 Mixing Processes Convection Rotation Atomic diffusion Magnetic fields •Are weak magnetic fields in A&F stars ubiquitous? •What is the origin? •One or multiple origins? Magnetic fields Mixing Processes Convection Rotation Atomic diffusion Magnetic fields Magnetic fields in intermediate-mass stars 90% 10% 60% 40% Surface magnetic fields detected in 10% of A/F (mostly Ap stars) Core magnetic fields (20-1000 kGauss) detected in 60 % of RG stars with masses between 1.4 - 2 M⊙ 20% 80% Magnetic fields in >20% of White Dwarfs •Pure DSCT IS in the Cep-Her Complex! •Teff-“𝜈max” relation too weak to be useful Rotation & diffusion & ensemble analyses Rotation & diffusion & ensemble analyses Rotation & magnetic fields In a rapidly rotating star, an inertial mode in the convective core can resonantly couple with a gravity mode propagating in the surrounding radiative zone. Rotation & age & ensemble analyses In memoriam Wojciech Dziembowski (1940-2025) •Effects of magnetic fields on stellar pulsations (ro Ap stars and the Sun)! •Excitation of pulsations in DSCT & 𝛽 Cep stars! •The excitation and damping of solar gravity modes! •Rotation of the Sun and other stars! •Nonlinear matters! •… A pioneer in stellar pulsation theory, whose work laid the foundation for modern asteroseismology.! Thank you Thank you!