James Webb Space Telescope Feed Post

Arxiv: JWST/MIRI detection of a carbon-rich chemistry in a solar nebula analog Published: 10/23/2024 9:00:15 PM Updated: 10/23/2024 9:00:15 PM

Paper abstract: It has been proposed, and confirmed by multiple observations, that disksaround low mass stars display a molecule-rich emission and carbon-rich diskchemistry as compared to their hotter, more massive solar counterparts. In thiswork, we present JWST Disk Infrared Spectral Chemistry Survey (JDISCS) MIRI-MRSobservations of the solar-mass star DoAr 33, a low-accretion rate T Tauri starshowing an exceptional carbon-rich inner disk. We report detections of H_2O,OH, and CO_2, as well as the more complex hydrocarbons, C_2H_2 andC_4H_2. Through the use of thermochemical models, we explore differentspatial distributions of carbon and oxygen across the inner disk and comparethe column densities and temperatures obtained from LTE slab model retrievals.We find a best match to the observed column densities with models that havecarbon enrichment, and the retrieved emitting temperature and area ofC_2H_2 with models that have C/O = 2-4 inside the 500 K carbon-richdust sublimation line. This suggests that the origin of the carbon-richchemistry is likely due to the sublimation of carbon rich grains near the sootline. This would be consistent with the presence of dust processing asindicated by the detection of crystalline silicates. We propose that thislong-lived hydrocarbon rich chemistry observed around a solar-mass star is aconsequence of the unusually low M-star-like accretion rate of the centralstar, which lengthens the radial mixing timescale of the inner disk allowingthe chemistry powered by carbon grain destruction to linger.