Atmospheric composition of stars AF Leporis A and Epsilon Indi A characterized

Star system: AF Leporis | Distance from the Sun: 87.5 light years

Understanding how planets form requires detailed knowledge of the chemical makeup of their host stars. This study provides a comprehensive analysis of the host stars AF Leporis A and Epsilon Indi A, which are known to harbor cold, directly imaged planets. By examining the light from these stars with high-resolution spectroscopy—a technique that breaks down starlight into its component colors to identify chemical elements—the composition of their atmospheres has been mapped in high detail.

The research utilized data from the Gemini/GHOST instrument to measure the concentrations of 16 different elements, including carbon, oxygen, and sulfur. The team employed two distinct analytical methods to calculate stellar temperature and surface gravity, identifying variations of up to 260 Kelvin between different calculation techniques. This rigorous approach ensures a precise baseline for chemical comparison.

By comparing the chemical ratios of the stars with those of their orbiting planets, AF Leporis b and Epsilon Indi Ab, the study provides clues about how these worlds originated. The planets show higher concentrations of heavy elements compared to their parent stars, which suggests they grew through core accretion. This process involves the gradual buildup of solid material in a protoplanetary disk before gas is captured.

Key findings
- Precise measurement of 16 elements in the atmospheres of AF Leporis A and Epsilon Indi A.
- Solar-like ratios of carbon, oxygen, and sulfur confirmed for both host stars.
- Comparison of stellar and planetary abundances points to core-accretion formation for companion planets.
- Analysis revealed discrepancies in stellar temperature calculations of up to 260 Kelvin depending on the method used.

Scientific study

A High-Resolution Spectroscopic Survey of Directly Imaged Companion Hosts: III. Characterization of the Cold Imaged Planet Hosts AF Lep A and ε Indi A (external link)