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AR 16142 (Archival Research)

Thu Jul 25 13:16:00 GMT 2024

Principal Investigator: Joshua Lothringer
PI Institution: Space Telescope Science Institute
Investigators (xml)

Title: The First Grid of White-Dwarf-Irradiated Brown Dwarf Atmosphere Models
Cycle: 28

Abstract
Highly irradiated brown dwarfs (BDs) provide essential tests to models of brown dwarf atmospheric physics. While only a handful have been discovered, BDs in ultra-short period orbits around white dwarfs (WDs) are a physically interesting and observationally favorable class of irradiated substellar objects, reaching equilibrium temperatures matching or exceeding their internal heat. Recently, HST Program 15947 was approved to execute the first survey of such objects. Currently, however, no self-consistent BD atmosphere models exist that take into account the extreme UV irradiation from a WD host. We propose to calculate the first grid of self-consistent atmosphere models and synthetic spectra for Program 15947's six targets to strengthen the theoretical expectations for how the atmosphere's of these informative objects behave under such extreme conditions. We will investigate the interplay between extreme irradiation and high internal heat, as well as the sensitivity of emergent spectra to intrinsic properties like the internal temperature, efficiency of heat transport, albedo, surface gravity, and metallicity. The grid will also enhance the interpretation of other existing HST datasets, including observations of two brown dwarfs around main-sequence stars and the large collections of hot Jupiter and isolated brown dwarf spectra. Future observations with JWST of these various classes of substellar object will also benefit from this investigation.