Exoplanet Host Stars

"Know thy star, know they planet" - it's true! The Cool Star Lab works with the SPECULOOS Consortium to characterize low-mass exoplanet host stars, typically M dwarfs near the Sun. Our most famous case is TRAPPIST-1, but we've contributed to the characterization of many other stellar hosts to rocky, icy, and gassy worlds, using optical and infared spectroscopy to infer composition, age, and evidence of magnetic activity. Our program also uncovers rare low-mass eclipsing binaries that are critical for testing evolutionary and structure models of stars and brown dwarfs.

Recent Research Results

A rare giant planet orbiting an M dwarf

(Oct 2023) Adam Burgasser contributed to the analysis of another giant planet orbiting a metal-rich early-M dwarf TOI-4201. The exoplanet, weighing in at 2.5 Jupiter masses and with an orbit period of just 3.6 days, occupies a sparse region in planet mass and separation among M dwarf systems (read the AJ article by Gan et al.). 

Lowest-mass host star to a giant exoplanet

(Sep 2023): Adam Burgasser analyzed the optical spectrum of the host star to the newly-discovered giant exoplanet TOI-4860b. The Magellan/MagE spectrum revealed this source to be an inactive, slightly metal-rich M4.5 dwarf, making it the lowest-mass star known to host a giant planet (read the MNRAS article by Triaud et al.).  

A New Super-Earth planet orbiting an M dwarf

(Sep 2023): Cool Star Lab team members helped to characterize the low-mass stellar host to a new Super Earth planet. The star, TOI-1680, was found to be an inactive M4.5, right at the fully convective stellar mass boundary. The planet, TOI-1680b, has a radius about 50% larger than Earth, and is also warmer with a 400 K equilibrium temperature. The relatively bright primary and favorable radius ratio makes this an important new target for atmospheric characterization with JWST (read the A&A article by Ghachoui et al.). 

Planet host star has a dim companion

(Jun 2023): Adam Burgasser and Carl Melis obtained Lick/Kast optical spectra for one of two new low-mass planet host stars identified in TESS + SPECULOOS. The star, TOI-2084, has a previously unrecognized co-moving, low-mass stellar companion 1400 AU away, giving the 6.7 Earth-mass planet a second "dim red bulb" to illuminate it (read the preprint by Barkaoui et al.). 

The host star of the habitable zone Super-Earth TOI-715b

(May 2023): Adam Burgasser and Christian Aganze helped characterize a new low-mass exoplanet host star TOI-715, an old M4 dwarf that hosts a super-Earth planet in its habitable zone. Adam analyzed optical spectra obtained with Magellen/LDSS-3C, while Christian used GALAH data to statistically constrain the star's age (read the prepint by Dransfield et al.)

The exoplanet host star TOI-2096

(Mar 2023): Cool Star Lab researchers helped characterize the low-mass stellar host of the double-planet system TOI-2096. TESS and ground-based monitoring show that this system contains both a super-Earth and a mini-Neptune orbiting a star less than a quarter the mass of the Sun. The CSL team obtained optical spectroscopy with Kast on the Lick Shane Telescope that determined the host star's spectral type, temperature, and metallicity. (read the paper by Pozuelos et al. at Astronomy & Astrophysics).