Stars, Planets, and ISM Seminar

Mar

2025

12:00 pm – 1:00 pm

In Person (view details)

Two talks by Astronomy Department graduate students

Description

James Mang, The University of Texas at Austin

New Atmospheric Models for the Coldest Directly-Imaged Planets and Brown Dwarfs

JWST has provided unprecedented access to ultra-cool brown dwarfs and has pushed the boundaries of directly imaging temperate giant planets. It has now directly imaged benchmark planets such as Eps Indi Ab and 14 Her c, but early JWST observations of these systems have revealed that they are significantly fainter than expected around 4 microns. This suggests that additional atmospheric processes—such as chemical disequilibrium and clouds—are playing a key role in shaping their emergent spectra. As we continue to investigate these objects and other JWST surveys push its limits to detect sub-Saturn and Neptune-sized planets, it is crucial to develop atmospheric and evolutionary models that better capture the atmospheric complexity and diversity of planetary properties of objects like Jupiter, Saturn, and Neptune. Here, I will present the development of Sonora Flame Skimmer and Sonora Gila Monster, the next generation of Sonora atmospheric and evolutionary models. These new grids extend to much colder temperatures, incorporate cloud formation, and account for chemical disequilibrium across a wide range of metallicities and C/O ratios. I will also discuss how we have used these models to better fit data from several ongoing JWST programs, including those targeting WISE 0855, WD 1856b, Eps Indi Ab, 14 Her c. These models will be critical for refining our understanding of ultra-cool substellar objects and guiding future JWST observations by providing accurate flux predictions across key bandpasses. Their application will help optimize observational strategies and deepen our insight into the atmospheric physics of these distant worlds.

Erica Sawczynec, The University of Texas at Austin

A Monolithic Cross-Dispersed Grism Design for Near-Infrared Spectroscopy

As space-based missions increase in cost, size, and time to build, it is becoming increasingly important to innovate technology that allows for the development of compact and lightweight instruments with simple designs that enable high-quality science. Grisms have become a popular optic for use in imaging-spectrograph instruments (e.g. WFC3 on Hubble & NIRCam on JWST), but most of the existing instruments only offer low-resolution spectroscopy and can require a secondary filter wheel containing a separate dispersing optic, which introduces light-loss, spurious reflections, and alignment issues. In this talk I discuss the design of a first-of-its-kind silicon monolithic cross-dispersed grism with a high-order grating on the entrance face and a low-order cross disperser on the exit face.

Location

PMA 15.216B and online

Audience

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