Research

I study transiting M dwarf exoplanets and stellar activity as a member of Zach Berta-Thompson's CU Boulder Exoplaneteers (CUBE) research group. My work has included ground-based discovery and characterization of transiting exoplanets, stellar characterization, space-based spectroscopy of exoplanet atmospheres, and the study of starspots and their contaminating effects on exoplanet transmission spectra.

Following the launch of TESS, I led a ground-based followup campaign using the Las Cumbres Observatory global network to confirm or rule out planet candidates. The first transit I observed was of ultra-short period M dwarf exoplanet LHS 3844b (Vanderspek+ 2019), which became the first published rocky exoplanet found by TESS.

My observations have led or contributed to several other discoveries of M dwarf exoplanets like the nearby Earth-sized planet LP 791-18 d (Peterson+ 2023) and the earlier discovery of planets LP 791-18 b and c (Crossfield+ 2019), the TOI 2096 system (Pozuelos+ 2023), and the sub-Neptunes TOIs 122b and 237b (Waalkes+ 2021). Each of these worlds is a viable candidate for atmospheric characterization with current or near-future observational instruments.

Exoplanet atmospheres are difficult to detect and characterize, and one way to search for them is by looking for atmospheric outflow of hydrogen from sub-Neptune exoplanets that orbit close to active host stars. I looked for evidence of neutral hydrogen outflow from rocky exoplanet GJ 1132b (Berta+ 2013).

Highlighted Work:


TOI 122b and TOI 237b, Two Small Warm Exoplanets Orbiting Inactive M Dwarfs Found by TESS

Ly╬▒ in the GJ 1132 System: Stellar Emission and Planetary Atmospheric Evolution

A temperate Earth-sized planet with tidal heating transiting an M6 star

A Super-Earth and Sub-Neptune Transiting the Late-type M Dwarf LP 791-18

Identification of carbon dioxide in an exoplanet atmosphere

A Low-mass, Pre-main-sequence Eclipsing Binary in the 40 Myr Columba Association-Fundamental Stellar Parameters and Modeling the Effect of Star Spots

TESS Discovery of an Ultra-short-period Planet around the Nearby M Dwarf LHS 3844

A super-Earth and a mini-Neptune near the 2:1 MMR straddling the radius valley around the nearby mid-M dwarf TOI-2096

TOI-269 b: an eccentric sub-Neptune transiting a M2 dwarf revisited with ExTrA

Teaching

ASTR 3710: Solar System Formation & Evolution, Fall 2021
Instructor: Dr. Meredith MacGregor

ASTR 1040: Accelerated Intro Astronomy II, Spring 2021
Instructor: Dr. Erica Nelson

ASTR 3510: Observation & Instrumentation, Fall 2020
Instructor: Dr. John Bally

Courses:
ASTR 3400: Astronomy Research Methods, Fall 2018
Instructor: Dr. Zachory Berta-Thompson

Contact

Email: william.waalkes@colorado.edu

Office: Duane D245