The Discovery of Three Nearby Planetary Systems, and a Population of Ancient Jovians Orbiting Stars in the Galactic Thick Disk

Abstract

In the first part of my thesis, I present the detection of three individual planetary systems: First, I present the analysis of HARPS-N, CARMENES, and HIRES radial velocities of HD 79210 and HD 79211. I conclude that there is a planet orbiting HD 79211, with a period of 24.422$\pm$0.014 days, and a minimum mass of 10.6$\pm$1.2M$\oplus$. This system demonstrates the feasibility of planet formation around one member of a 130-AU binary. Second, I present an analysis of the 0.88R$\oplus$ planet with a period of 7.577 days orbiting the nearby M1V star GJ 341, which is the target of JWST observations. I constrain the planetary mass to an upper limit of 4.0 M$\oplus$ (3$\sigma$), ruling out the presence of an additional companion with a minimum mass greater than 15.1 M$\oplus$, and a period of less than 1750 days. I further found disagreement in the spectroscopically- and photometrically-determined stellar rotation periods. Third, I present the discovery of the planetary system of the bright (V = 7.2), nearby, Sun-like star HD 60779. I report two TESS transits and a CHEOPS transit of HD 60779b, a sub-Neptune with a radius of 3.25$\pm$0.10R$\oplus$ on a 30-day orbit. I use HARPS-N RVs to measure the mass of 14.7$\pm$1.0 M$\oplus$, and further discover a second planet, HD 60779c, with an orbital period of 104 days. The extreme systemic RV of HD 60779 makes it very promising for atmospheric-escape studies via the LyA feature. In the second part of this work, I present a homogeneous analysis of 268 confirmed and candidate transiting hot Jupiter hosts in the northern hemisphere, with effective temperatures ranging from 4800-6200 K. I combine high-resolution spectra from the Mt. Hopkins/TRES instrument, Gaia astrometry, and photometry from Gaia, 2MASS and WISE to determine the parameters of these stars, notably their [alpha/Fe] and [Fe/H]. I proceed to classify the stars as members of the thin or thick disks, from which I identify two confirmed and three candidate hot Jupiters around thick-disk hosts. My catalog is the largest sample of chemically-identified thick-disk hot-Jupiter hosts, allowing the community to begin follow-up of these ancient Jovians as laboratories for probing planet formation in the early Galaxy.