Astronomy & Astrophysics Seminar

Zoom: https://tau-ac-il.zoom.us/j/87185167411?pwd=FpTUyIgXaOturzOFSetA6pPVYQilen.1

Speaker 1: Noy Ben Yehuda

The stellar context of small planets: host star properties as predictors of planetary radii

Abstract:

The relationship between the properties of planet-hosting stars and planetary radii is crucial for advancing our understanding of exoplanet formation and evolution. In our work, we focus on the Fulton Gap - a distinct dip in the distribution of exoplanet radii between 1.5 and 2 Earth radii, a feature that may offer valuable clues about the processes shaping planetary evolution. Our study investigates the physical and chemical factors that may contribute to this radius valley. By leveraging high-resolution spectroscopic data from the GALAH survey, we examine whether host-star properties exhibit any statistical relationship with planet radii in the vicinity of the Fulton Gap, and how they might affect planetary formation and evolution.

We found a strong correlation between planet radius and stellar age, as well as with certain elemental abundances, particularly the highly volatile elements carbon (C), nitrogen (N), and oxygen (O).
Our findings may help refine models of Earth-like planet formation and evolution, and provide a foundation for understanding the interplay between stellar environments and planetary characteristics. Future work will focus on expanding the dataset, improving the determination of stellar elemental abundances and ages, and linking the Fulton Gap to the broader context of exoplanet formation theories.

Speaker 2: Eyal Hadad

Binary and Tidal Locking Synchronization

Abstract:

We identified two groups of main---sequence binary stars observed by Gaia and GALAH, respectively, based on their excess luminosity on the CMD, and we show that some of these binary systems present high rotational velocity. We assume the rotational-velocity excess is due to the inability to resolve the two stars in the combined spectrum.

Additionally, we examined 669 short-period eclipsing binary systems and used rotational velocity and radii measurements to deduce the rotational period of the primary stars. We find compelling evidence of synchronization up to an orbital period of three days, where the primary’s rotational period matched the period of the orbital motion.
 

Seminar Organizer: Dr. Jonathan Stern