Dissertation

Dwarfing Expectations: The Rapid Expansion of the Transiting Brown Dwarf Population in the Era of the Tess Mission

Carmichael, Theron W

2021

Overview

This thesis presents an analysis of transiting brown dwarf (BD) systems and examines their effectivenessas tests to substellar evolutionary models. The radius, mass, and age of transiting BDsystems are the parameters most useful in testing these models and in this work, I show how mycollaborators and I have used three facilities to derive these parameters for transiting BD systems.These facilities are: 1) NASA’s Transiting Exoplanet Survey Satellite (TESS) mission, 2) the TillinghastReflector Echelle Spectrograph (TRES), and 3) ESA’s Gaia mission. In this work, I use TESS,TRES, and Gaia in tandem to detect and characterize 10 new transiting BD systems with preciseradius, mass, and age determinations (in most cases). Most of the age determinations in this workcome solely from stellar isochrone models of the host star, but several systems have age constraintsfrom stellar clusters and gyrochronology, which we use to constrain the youth of one transiting BD,TOI-811b, to less than 200 Myr. This is important because it is at these young ages when the radii ofBDs changes most rapidly. In addition, I apply parallax measurements from the Gaia mission’s second data release (GaiaDR2) to improve the radius determinations of 10 transiting BD systems published prior to GaiaDR2 and the launch of the TESS mission. For these 10 previously published systems, new lightcurves from TESS are used, when possible, and the stellar distances, luminosities, and radii areupdated with the parallaxes from Gaia DR2, which improves our constraint on the companionBD’s radius. This work has significantly improved the radius determinations of 7 previously knowntransiting BDs, including CoRoT-15b and AD 3116b, whose radius uncertainties have been improvedfrom 15% to 5-7%, making them much more effective for testing substellar evolutionary models. Using these 20 new and previously known transiting BD systems, I have shown that the substellarevolutionary models ranging from young to old substellar isochrones are generally able toreproduce the observed radius, mass, and age determinations of the known transiting BD population.

• Publisher: ProQuest Dissertations & Theses
• Subject: Age / Astronomy / Astrophysics / Graduate students / Light / Marathons / Velocity
• ISBN: 9798534682397