Wednesday, March 20, 2024, 12:00pm - 01:00pm
This repeat is an exception to the normal repeat pattern
Bryce Hobbs, The University of Texas at Austin
Development of an Improved Higher-Order Correction for the NIF Oxygen Opacity Experiments
Abstract
X-ray opacity measurements on the National Ignition Facility (NIF) are in the process of measuring oxygen and iron plasmas at HED conditions. These measurements have the potential to revise our understanding of the solar convection zone boundary problem and of white dwarf stars by probing plasma conditions at the base of their convection zones. Accurate opacity measurements using soft X-ray Bragg crystal spectrometers require correction for higher-order diffraction effects. Extending prior work in this area, we are developing a new method to correct for the higher-order effects in the NIF opacity measurements.
Malia Kao, The University of Texas at Austin
Hunting for Polluted White Dwarfs using Gaia XP Spectra and UMAP
Abstract
Nearly all stars that host exoplanets are intermediate- to low-mass stars. This means most exoplanetary hosts will end their lives as a white dwarf (WD) star. Some of the exoplanets can survive engulfment during the host star's giant phases and become tidally disrupted during the WD evolutionary track, eventually being accreted onto the surface of the WD. Because of the overall spectral purity of WD atmospheres, actively or recently accreted material can be studied using the spectra of these polluted WDs. This provides us a unique opportunity to get a direct look into the interiors of exoplanets. Using 96,134 WDs in Gaia DR3 with BP-RP (XP) spectra, we constructed a 2D map using a uniform manifold approximation and projection (UMAP) algorithm to organize the WDs into identifiable spectral regions. The polluted WDs are among the unique spectral groups identified in our map. This type of candidate selection method could potentially increase the number of known WDs with 5 or more metals in their atmospheres from ~ 36 to ~ 375.
Location: PMA 15.216B and online
