A warm Jupiter transiting an M dwarf: A TESS single transit event confirmed with the Habitable-zone Planet Finder

TL;DR

This paper confirms a warm Jupiter exoplanet transiting an early M dwarf star using TESS data and high-precision infrared spectroscopy, marking the lowest-mass star known to host such a planet.

Contribution

It presents the first confirmation of a warm Jupiter orbiting an early M dwarf, combining multiple observational techniques for validation.

Findings

Confirmed a warm Jupiter with 0.66 M_J and 1.15 R_J orbiting an M0 star.

Discovered the host star is the lowest-mass star known with a transiting warm Jupiter.

Identified the planet as a puffy warm Jupiter with an equilibrium temperature of ~362 K.

Abstract

We confirm the planetary nature of a warm Jupiter transiting the early M dwarf TOI-1899, using a combination of available TESS photometry; high-precision, near-infrared spectroscopy with the Habitable-zone Planet Finder; and speckle and adaptive optics imaging. The data reveal a transiting companion on an $\sim29$-day orbit with a mass and radius of $0.66\pm0.07\ \mathrm{M_{J}}$ and $1.15_{-0.05}^{+0.04}\ \mathrm{R_{J}}$, respectively. The star TOI-1899 is the lowest-mass star known to host a transiting warm Jupiter, and we discuss the follow-up opportunities afforded by a warm ($\mathrm{T_{eq}}\sim362$ K) gas giant orbiting an M0 star. Our observations reveal that TOI-1899.01 is a puffy warm Jupiter, and we suggest additional transit observations to both refine the orbit and constrain the true dilution observed in TESS.