Date of Award
Doctor of Philosophy (PhD)
Physics and Astronomy
We present the results of a high precision infrared radial velocity (RV) search for hot-Jupiters around young stars in nearby young clusters and Moving Groups. Utilizing high resolution infrared spectroscopy with Gemini South Phoenix and VLT CRIRES, we targeted a sample of 28 young stars. Our second survey was of 38 young stars observed with Keck NIRSPEC. Our technique for determining RVs for young stars utilizes telluric features as an absolute wavelength reference. With this technique, we have been able to achieve RV precisions of 22-31 m/s with Gemini Phoenix, 32-63 m/s with VLT CRIRES, and 41-182 m/s with Keck NIRSPEC on single field stars.
With Gemini Phoenix and VLT CRIRES, we identified TWA 13A and ScoPMS 13 as candidate RV variables. We identified two spectroscopic binaries (RXJ1204.7-7731 and 1RXS J195602.8−320720). We show initial orbital fits for RXJ1204.7-7731, that show a ~5.5 day period with and eccentricity of ~0.1, and a mass ratio of KA/KB = 0.37. Initial orbital fits for 1RXS J195602.8−32072019 show a nearly equal mass system, with a mass ratio of KA/KB=0.97, with a ~19 day period and an eccentricity of ~0.2.
In our Keck NIRSPEC sample, we report a young (~10 Myr) candidate hot Jupiter in Upper-Scorpius around RXJ 1540.9-3024, and present an initial orbit for planet RXJ 1540.9-3024b as having a 10.7 day period with an eccentricity of 0.28 and an Msini of 5.4 MJ. We also report the discovery of two spectroscopic binaries, RXJ 1548.9-3045 and V1096 Tau, but our temporal sampling was insufficient to obtain orbital solutions.
We use the sample of known stars and brown dwarfs within 5 pc of the Sun, and AFGK stars within 10 pc, to determine which stellar spectral types provide the most empirical habitable zone, or EHZ. M stars provide more EHZ real estate than other spectral types, possessing 36.5% of the habitable real estate en masse. K stars are second with 21.5%, while A, F, and G stars offer 18.5%, 6.9% and 16.6%, respectively. If Earth-like planets are as common around low mass stars as Kepler results suggest, M stars are the most likely place to find Earth-like planets in habitable zones.
Cantrell, Justin, "Young Stars, Young Planets, and Habitable Zones." Dissertation, Georgia State University, 2018.