STScI Research | STScI Discovery Seminar Series - Nicole Arulanantham (STScI) and Emily Rickman (STScI) @stsciresearch6722 | Uploaded 2 years ago | Updated 4 hours ago
This Discovery Seminar features talks by Nicole Arulanantham (STScI) on LyA Scattering in T Tauri Systems: Insights from HST's ULLYSES Program and Emily Rickman (STScI) on Bridging Exoplanet Detection Techniques Toward Comprehensive Characterization of Directly Imaged Exoplanets.
Tuesday, May 31 2022
Speaker: Nicole Arulanantham
Title: LyA scattering in T Tauri systems: insights from HST’s ULLYSES program
Abstract: T Tauri systems, the young precursors to Sun-like stars, display broad LyA emission lines that are generated at their accretion shocks. Although the features are heavily absorbed by H I in stellar outflows and the ISM, the integrated line fluxes make up nearly 90% of the total UV radiation field that reaches the protoplanetary disks surrounding the stars. Since UV photons are critical regulators of gas-phase chemistry in these environments, characterizing the LyA emission from T Tauri stars provides important constraints on the temperatures and abundances of disk surface layers. Here we explore the impact of including resonant scattering in models fit to the observed LyA profiles, in an effort to better characterize the column densities and velocities of intervening H I. Our sample consists of targets in Data Releases 1, 2, and 3 of the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) program. The scattering models provide significantly better fits to the line profiles, but we find that the column densities of H I don’t change when scattering is included. Instead, we are able to extract more accurate velocities of absorbing H I, which we compare to other inner disk and accretion tracers.
Speaker: Emily Rickman
Title: Bridging Exoplanet Detection Techniques Toward Comprehensive Characterization of Directly Imaged Exoplanets
Abstracts: Very little is known about giant planets and brown dwarfs at an orbital separation great than 5 AU. And yet, these are important puzzle pieces needed for constraining the uncertainties that exist in giant planet formation and evolutionary models that are plagued by a lack of observational constraints. In order to observationally probe this mass-separation parameter space, direct imaging is necessary but faces the difficulty of low detection efficiency. To utilize the power of direct imaging, pre-selecting companion candidates with long-period radial velocities, coupled with proper anomalies from Hipparcos and Gaia, provide a powerful tool to hunt for the most promising candidates for direct imaging and comprehensively characterize such detections. Combining these exoplanet detection techniques removes the degeneracy of unknown orbital parameters, like the orbital inclination, leading to derived dynamical masses which can serve as benchmark objects to test models of formation and evolution. I present the detection and characterization of new directly imaged companions from VLT/SPHERE with derived model-independent precise dynamical masses by bridging together several exoplanet detection techniques, namely relative astrometry from direct imaging, radial velocities, and astrometry from Hippacros-Gaia eDR3 accelerations.
This Discovery Seminar features talks by Nicole Arulanantham (STScI) on LyA Scattering in T Tauri Systems: Insights from HST's ULLYSES Program and Emily Rickman (STScI) on Bridging Exoplanet Detection Techniques Toward Comprehensive Characterization of Directly Imaged Exoplanets.
Tuesday, May 31 2022
Speaker: Nicole Arulanantham
Title: LyA scattering in T Tauri systems: insights from HST’s ULLYSES program
Abstract: T Tauri systems, the young precursors to Sun-like stars, display broad LyA emission lines that are generated at their accretion shocks. Although the features are heavily absorbed by H I in stellar outflows and the ISM, the integrated line fluxes make up nearly 90% of the total UV radiation field that reaches the protoplanetary disks surrounding the stars. Since UV photons are critical regulators of gas-phase chemistry in these environments, characterizing the LyA emission from T Tauri stars provides important constraints on the temperatures and abundances of disk surface layers. Here we explore the impact of including resonant scattering in models fit to the observed LyA profiles, in an effort to better characterize the column densities and velocities of intervening H I. Our sample consists of targets in Data Releases 1, 2, and 3 of the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) program. The scattering models provide significantly better fits to the line profiles, but we find that the column densities of H I don’t change when scattering is included. Instead, we are able to extract more accurate velocities of absorbing H I, which we compare to other inner disk and accretion tracers.
Speaker: Emily Rickman
Title: Bridging Exoplanet Detection Techniques Toward Comprehensive Characterization of Directly Imaged Exoplanets
Abstracts: Very little is known about giant planets and brown dwarfs at an orbital separation great than 5 AU. And yet, these are important puzzle pieces needed for constraining the uncertainties that exist in giant planet formation and evolutionary models that are plagued by a lack of observational constraints. In order to observationally probe this mass-separation parameter space, direct imaging is necessary but faces the difficulty of low detection efficiency. To utilize the power of direct imaging, pre-selecting companion candidates with long-period radial velocities, coupled with proper anomalies from Hipparcos and Gaia, provide a powerful tool to hunt for the most promising candidates for direct imaging and comprehensively characterize such detections. Combining these exoplanet detection techniques removes the degeneracy of unknown orbital parameters, like the orbital inclination, leading to derived dynamical masses which can serve as benchmark objects to test models of formation and evolution. I present the detection and characterization of new directly imaged companions from VLT/SPHERE with derived model-independent precise dynamical masses by bridging together several exoplanet detection techniques, namely relative astrometry from direct imaging, radial velocities, and astrometry from Hippacros-Gaia eDR3 accelerations.
