Abstract Details

Name: Rahul Bandyopadhyay
Affiliation: Universidad de Chile (Nucleo Milenio YEMS)
Conference ID: ASI2025_346
Title : Polycyclic aromatic hydrocarbon abundances in T Chamaeleontis
Authors and Co-Authors : Rahul Bandyopadhyay 1, 2, Simon Casassus, 1, 2, 3, 4
Abstract Type : Poster
Abstract Category : Sun, Solar System, Exoplanets, and Astrobiology
Abstract : We investigate the protoplanetary disk around the T Tauri star T Chamaeleontis (T Cha). A significant amount of "see-saw" variability, i.e., relative decrease and increase of the fluxes short-ward and long-ward of 10 microns, respectively, is observed by comparing the mid-IR spectra of T Cha taken using Spitzer-IRS and JWST-MIRI-MRS. Multiple polycyclic aromatic hydrocarbon (PAH) bands around 6.2, 7.7-8.6, 11.3-12.7 microns can be prominently observed in the JWST spectrum compared to a faint 11.3-micron band in the Spitzer spectrum. We perform radiative transfer modelling to reproduce the mid-IR JWST spectrum and the photometric fluxes ranging from optical to far-infrared. We re-establish the geometric structure of the disk - an inner and an outer disk separated by a gap - as inferred from earlier Spitzer, VLT, and ALMA observations. We find that the reduction of the inner disk mass and scale height results in an increase of the outer disk irradiation and therefore, the increase in the outer disk emission, including the PAH bands, which supports the earlier explanation of "see-saw" variability observed in disks. We provide a new estimation of the PAH abundances in the disk of T Cha by fitting the PAH bands fluxes in a self-consistent way from the disk model. We put strong constraints on the PAH abundances by exploring a large range of physical conditions and structural parameters of both the inner and outer disk. We estimate a higher flaring index than the earlier models, which might result from the enhancement in the PAH emission and hence, increased gas heating than during the time of Spitzer observations. Our estimated PAH abundance also implies that the disk of T Cha might be undergoing FUV photoevaporation driven by its central star, providing possible constraints on the planet-formation time scale around T Cha.