Analysis of Molecular Variability Due to Accretion Bursts in the Protoplanetary Disk of Ex Lup as Observed with the James Webb Space Telescope

Protoplanetary disks are structures that form around a pre-main sequence star as a result of conservation of angular momentum during collapse of dense cores in star-forming regions. They accrete gas onto the central proto-star, and are the sites of planet formation. Early in their lifetime, disk experience variations in their accretion rate of gas onto the star, causing fluctuations in stellar UV radiation. EX Lup, the prototype of the EX Or class of T Tauri stars with high accretion variability, experiences burst and outbursts of high magnitude increases on short time scales (a few months to ~1yr). The 2008 outburst of EX Lup, observed with Spitzer Infrared Spectrograph (IRS), was analyzed in great detail to understand the mechanisms and effects of accretion outbursts on disk chemistry. However, no observations could be performed after outburst to study the postburst evolution. Using James Webb Space Telescope Mid-Infrared Instrument (MIRI) Cycle 1 programs GO-2209 and GO-4427 (PI: Peter Ábrahám, Co-I: Andrea Banzatti), mid-IR observations of EX Lup after the 2008 outburst were conducted in August 2022 and April 2023, following a March 2022 burst of ~1.6x magnitude increase from previous quiescence. In this thesis work, I compared the new MIRI epochs to IRS epochs of quiescence (April 2005) and outburst (April 2008). Using the Interactive Spectral Analysis Tool (iSLAT), I analyzed the spectra of organics and water emission and found that they returned to quiescent levels after their extreme changes during outburst. I also compared to a sample of ~60 disks observed using IRS, showing that the variation of molecular emission as a function of time in EX Lup may provide insight into the spread of trends seen in the larger sample. The variability in the cold to hot water ratio in EX Lup shows evidence for a snowline recession that caused a burst in ice sublimation during outburst.

Author dc:creator

• Smith, Sarah A.

Contributors dc:contributor

• Banzatti, Andrea
• Togi, Aditya
• Rangelov, Blagoy

• circumstellar matter
• protoplanetary disks
• stars
• pre-main sequence

Language dc:language

en

Identifier

Smith, S. A. (2024). Analysis of molecular variability due to accretion bursts in the protoplanetary disk of ex lup as observed with the James Webb Space Telescope [Master's thesis, Texas State University].

OAI identifier oai:identifier

oai:tdl-ir.tdl.org:10877/19301