Research Projects
Dynamical Architectures of Transiting Planets with Planetary and Stellar Companions
Advised by Prof. Dan Huber and Prof. Lauren Weiss
Keyword: exoplanet in binary; orbital dynamics; transit; radial velocities; astrometry
How do transiting planets form and evolve in the presence of stellar and substellar companions? Previous surveys have found a deficit of s-type (circumstellar) planets in close binaries (<100AU), suggesting that close companions inhibit planet formation. However, some planets survive in such dynamically challenging environments for reasons that are still unclear. A new tool to characterize the stellar and substellar companions in planetary systems is the Hipparcos-Gaia astrometric acceleration catalog, which identifies stars with with companions from 1-50 AU based on their astrometric accelerations.
I constructed a volume-limited catalog up to 300 pc of 66 stars hosting transiting planets from Kepler, K2, and TESS with significant Hipparcos-Gaia astrometric acceleration, which indicates the presence of planetary or stellar companions. I have been observing these stars using the Keck instruments HIRES, KPF, and NIRC2 since 2021. The survey has yielded 32 stellar companions and 8 planetary-mass candidates, with more discoveries forthcoming.
Direct Characterization of Exoplanets with Imaging
Fourier Transform Spectroscopy
Advised by Prof. Michael Bottom
Keyword: direct imaging; spectrograph; Habitable World Observatory
The Decadal Survey on Astronomy and Astrophysics 2020 (NASEM, 2021) recommends a direct imaging telescope, i.e., Habitable Worlds Observatory (HWO) as the top priority mission for the next decade. The mission aims at detecting and obtaining spectra from ~25 habitable planets at optical and near-infrared wavelengths. A key challenge for this science is the faintness of Earth-like exoplanets, with plant-star flux ratios on the order of 10e-10. Integral field spectrographs (IFS) have been a popular choice for these mission concepts. However, multiple studies have revealed that detector noise is a serious obstacle for such instruments when observing extremely faint targets such as exoplanets (Robinson+2016). As the second component of my thesis, I explored an alternative option of using imaging Fourier transform spectrographs (iFTS), which are less sensitive to detector noise, to directly characterize exoplanet atmospheres from space.
Simulated direct image of the inner Solar System at 10 pc and spectra from Earth-like and Jupiter-like planets. Figures adapted from Gaudi et al. 2020 and The LUVOIR Team, 2019.
My simulations show that for a 6-meter telescope, an IFS outperforms an iFTS at optical wavelengths because an iFTS suffers higher photon noise. In the near-IR, the relative efficiency between an IFS and iFTS depends on the instrument design and detector noise . An iFTS will be more efficient than an IFS if the readout noise of the near-IR detector is above ~3 electron/pix/frame, which is half of the noise from state-of-the-art near-IR detectors today. However, if the readout noise is further reduced below this threshold, the performance of an IFS will experience a substantial improvement and become more efficient. These results highlight the need for developments to reduce detector noise to achieve the goal of spectrally characterizing habitable planets.