Colloquium on Apr. 3, 2024

Chemical Evidence of Planetary Ingestion in Binary Stars

Speaker: Fan Liu (Monash University)

Venue: SWIFAR Building 2111

Time: 15:00 PM, Wednesday, Apr. 3, 2024

Abstract:

Ingestion of planetary material and/or planet formation can imprint a distinct chemical signature on the host star’s photosphere. Detecting these ‘planet signatures’, however, is challenging due to unknown occurrence rate, small signal amplitudes and heterogeneous star samples with large differences in stellar ages. Binary star systems offer a unique opportunity to detect stellar chemical signatures of planets thanks to their shared origin and identical chemical composition. Here we establish and report high-precision chemical abundances (~ 0.015 dex; 3%) for a large, homogeneous sample of 125 pairs of stars moving together (91 with shared origin, i.e., co-natal) with a well defined selection function using Gaia DR3. Our sample represents a ten-fold increase in sample size and a least five-fold increase in precision over traditional spectroscopic analysis of binary star systems. We identified at least 7 new instances of planetary ingestion, corresponding to an occurrence rate of about 8%. An independent Bayesian indicator was deployed, which can effectively disentangle the planet signatures from other factors, such as random abundance variation and atomic diffusion. Our study thus provides direct evidence of planet signatures and facilitates a deeper understanding of the star–planet–chemistry connection by providing observational constraints on the mechanisms of planet engulfment, formation and evolution.

Report PPT:  SWIFAR_Fan Liu.pdf