Current ResearchExoplanets

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Here, we present pterodactyls , a data reduction pipeline specifically built to address the challenges in discovering exoplanets around young stars and to work with TESS Primary Mission 30-min cadence photometry, since most young stars were not pre-selected TESS 2-min cadence targets. We search five clusters with known transiting planets: Tucana-Horologium Association, IC~2602, Upper Centaurus Lupus, Ursa Major and Pisces Eridani. We show that pterodactyls recovers seven out of the eight confirmed planets and one out of the two planet candidates, most of which were initially detected in 2-min cadence data. For these clusters, we conduct injection-recovery tests to characterize our detection efficiency, and compute an intrinsic planet occurrence rate of 49% for sub-Neptunes and Neptunes (1.8-6 Rearth) within 12.5 days, which is higher than Kepler's Gyr-old occurrence rates of 6.8%. This potentially implies that these planets have shrunk with time due to atmospheric mass loss. 

The goal of this project was to calculate the occurrence of giant planets (GPs) using radial velocity (RV) data and compare it to that of Kepler's, which I found overlap well within the uncertainties. Additionally, using the Exoplanet Population Observation Simulator (EPOS), I discovered that the RV GP distribution has a turnover around the snow line. An extrapolation of this distribution out to ~100 au produces an occurrence rate that is consistent with observed direct imaging rates. This result has proven to be important since previous calculations of occurrence rates have consistently over-predicted direct imaging rates by at least an order of magnitude. This result has also shown that GPs are not always the cause of disk structures as previously thought since GPs occur far less frequently than disk structures.

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Here, we calculate the mass and spatial scale of solid material around Sun-like stars probed by transit and radial velocity exoplanet surveys and compare those to the observed dust masses and sizes of Class II disks in the same stellar-mass regime. We show that the apparent mass discrepancy disappears when accounting for observational selection and detection biases. We find a discrepancy only when the planet formation efficiency is below 100%, or if there is a population of undetected exoplanets that significantly contributes to the mass in solids. We identify a positive correlation between the masses of planetary systems and their respective orbital periods, which is consistent with the trend between the masses and the outer radii of Class II dust disks. This implies that, despite a factor 100 difference in spatial scale, the properties of protoplanetary disks seem to be imprinted on the exoplanet population.

Here, we analyze the CORALIE/HARPS sample of exoplanets found by the Doppler radial-velocity method for signs of the predicted gap or "desert" at 10-100 Mearth caused by runaway gas accretion at semi-major axes of <3 au. We find that these data are not consistent with this prediction. This result is similar to the finding by the MOA gravitational microlensing survey that found no desert in the exoplanet distribution for exoplanets in slightly longer period orbits and somewhat lower host masses (Suzuki et al. 2018). Together, these results imply that the runaway gas accretion scenario of the core accretion theory does not have a large influence on the final mass and semimajor axis distribution of exoplanets.

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The goal of this project was to calculate the occurrence of giant planets (GPs) using radial velocity (RV) data and compare it to that of Kepler's, which I found overlap well within the uncertainties. Additionally, using the Exoplanet Population Observation Simulator (EPOS), I discovered that the RV GP distribution has a turnover around the snow line. An extrapolation of this distribution out to ~100 au produces an occurrence rate that is consistent with observed direct imaging rates. This result has proven to be important since previous calculations of occurrence rates have consistently over-predicted direct imaging rates by at least an order of magnitude. This result has also shown that GPs are not always the cause of disk structures as previously thought since GPs occur far less frequently than disk structures.

In this project, we computed the occurrence rates of planet with radii ~ 1-6 R   and periods <100 days versus planet-to-star mass ratio (q) and per stellar spectral type from the Kepler survey. We find that regardless of the spectral type, the occurrence rate can be described by a broken power-law. We also find that the position of this break and the power-law indices are the same for MGK dwarfs. Using EPOS, we find that the break in the power-law occurs at a value ~3-10 times lower than that identified by microlensing surveys (mostly low-mass stars) which implies that the most common planet inside the snow line is ∼3–10 times less massive than the one outside. With rocky planets interior to gaseous planets, the solar system broadly follows the combined mass-ratio function inferred from Kepler and microlensing.

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