Investigating circumstellar atomic radiation-driven dynamics in exoplanet and debris disc environments

Investigating Circumstellar Atomic Radiation-driven Dynamics in Exoplanet and Debris Disc Environments Alexandra Lehtmets 2. Year PhD, Young Research Fellow Supervisors: Mihkel Kama, Luca Fossati and Anna Aret SPA meeting 31.01.25 Contents: 2 Introduction and Motivation Model Methods Results Discussion Future work Introduction 3 Jermyn and Kama, 2018 - Found that low mass slowly rotating stars are most likely targets for observing stellar contamination. Fernandez, Brandeker and Wu, 2005 - Calculated gravitational and radiation pressure force acting on atoms and ions in β Pictoris case. Motivation Another way to look into the exoplanet atmosphere/debris disc chemical composition! 4 Methods 5 Main equations: 1. Calculation of beta ratio - Distance independent! 𝛽 = 𝐹𝑟𝑎𝑑 𝐹 𝑔𝑟𝑎𝑣 𝑣𝑖𝑜𝑛 = 𝛽 𝐺𝑀 𝑟2 1 Γ 2. Calculation of boost velocity - only neutral atoms, boost before being ionised 6 NIST atomic database (H to Ni) ATLAS9 fluxes 𝛽 = 𝐹𝑟𝑎𝑑 𝐹 𝑔𝑟𝑎𝑣 𝑣𝑖𝑜𝑛 = 𝛽 𝐺𝑀 𝑟2 1 Γ I I, II, III MODEL INPUT TABELS FOR βAND 𝑣𝑖𝑜𝑛 SOLUTIONS OUTPUT XCOM (H to Ni) CMD ver. 3.7 evolutionary tracks Stellar masses STAR PARAMETERS 𝑇𝑒𝑓𝑓 ≈ 4,500 –19,000 K Age = 20 Myr Log g = 4.5 7 NEUTRAL Results (1) Radiation affects… -… noble gases (He, Ne, …) slightly -… non-metals (N, F, …) moderately -… metals (Li, Na, …) highly Results (2) 8 SINGLY IONISED Radiation affects… -… noble gases (He, Ne, …) slightly -… non-metals (N, F, …) moderately -… metals (Li, Na, …) highly Results (3) 9 Radiation affects… -… noble gases (He, Ne, …) slightly -… non-metals (N, F, …) moderately -… metals (Li, Na, …) highly DOUBLY IONISED Future work 16 •Model - Add stellar wind (Kral et al. 2023) - Quantify mass loss rates from the evaporating gas source - Assess potential accretion of material onto the host star - Apply the model to observed systems •Experimental (exoplanets) - Monitor host-star (6,500–8,000 K) spectra during exoplanet transit and secondary eclipse to detect potential contamination signatures - This model can give info about which lines should you look at in the spectra - Compare stellar chemical abundances before, during, and after transit/eclipse Thanks for listening! Questions? Feel free to ask me now or later! 17 Alexandra Lehtmets Young Research Fellow Tartu Observatory [email protected] linkedin.com/in/alexandra-lehtmets Where comes the β ratio? 18