The James Webb Space Telescope (JWST) has unveiled a fascinating insight into the chemical composition of protoplanetary disks. Our study focuses on two Classical T Tauri stars, GM Aur and RX J1615.3-3255 (J1615), both adorned with transitional disks. Despite their similar stellar and disk characteristics, these stars exhibit a striking contrast in carbon-bearing molecular emissions. By employing local thermodynamic equilibrium (LTE) slab models to analyze spectral lines within the 13.6-17.7 micron wavelength range, we discovered that J1615 displays strong emissions from H2O, HCN, C2H2, 12CO2, 13CO2, OH, and 13C12CH2, while GM Aur only shows H2O and OH. This disparity in carbon-rich chemistry is intriguing. We also measured the accretion rates of both stars using optical spectra and found that J1615's accretion rate is lower than GM Aur's. Furthermore, we utilized SED modeling to determine that J1615's disk contains higher concentrations of crystalline silicates and larger dust grains. The combination of lower accretion rate and larger, more processed dust grains in J1615's inner disk may be the key to the detection of carbon-rich gas. This discovery expands our understanding of the chemical diversity in planet-forming environments and highlights J1615 as a carbon-rich transitional disk. Our findings, accepted for publication in The Astronomical Journal, offer valuable insights into the complex interplay between stellar and disk properties and their impact on the chemical composition of protoplanetary disks. M. Volz, C. C. Espaillat, C. V. Pittman, S. L. Grant, T. Thanathibodee, M. McClure, B. Tabone, N. Calvet, and F. M. Walter.
