Constraining surface differential rotation in solar-like stars

Le résumé fourni par la source

Surface differential rotation is a key driver of magnetic activity in solar-like stars, yet its measurement from photometric data remains challenging. In this work, we apply the peak-height ratios (PHR) technique to constrain surface differential rotation. The method uses the ratio between the amplitudes of the second and first rotational harmonics in the periodogram of quasi-periodic flux modulations induced by active regions rotating across the stellar disc. This ratio depends on the latitude of the active regions and the stellar inclination, allowing each detected rotation period to be associated with a likely active-region latitude. We analyse a sample of 56 solar-like stars observed with long-cadence Kepler data, all with well-constrained inclinations from asteroseismology and detected rotational modulation. The sample includes 11 benchmark stars with independent asteroseismic measurements of differential rotation, enabling a direct validation of the method. For each target, we first construct star-specific relations between PHR and active-region latitude. We then identify robust harmonic pairs across independent light-curve segments and compute the respective observed PHR. These measurements together with the derived PHR relations are used to infer the surface differential rotation profile, including the equatorial rotation period and latitudinal shear, using weighted fitting and bootstrap uncertainty estimation. For the benchmark sample, the PHR-based shear values are consistent with asteroseismic results, supporting the reliability of the method despite the different depths probed by the two techniques. Across the full sample, we recover the expected trend of decreasing equatorial rotation period with increasing effective temperature. We also find that hotter, F-type stars tend to exhibit larger relative shear, with indications of a systematic increase above ~6000 K. Overall, our results demonstrate that the PHR technique provides a viable photometric diagnostic of surface differential rotation, enabling new constraints on stellar dynamos and magnetic activity across large stellar samples.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.