TOI-1859b: A 64-Day Warm Jupiter on an Eccentric and Misaligned Orbit

TL;DR

This paper reports the discovery and characterization of TOI-1859b, a warm Jupiter with a 64-day orbit, eccentric and misaligned, providing insights into its dynamical history and obliquity through spectroscopic observations.

Contribution

It presents the first measurement of stellar obliquity for a warm Jupiter with a long, eccentric orbit, using the Rossiter-McLaughlin effect, highlighting its dynamical origin.

Findings

TOI-1859b has an orbital eccentricity of 0.57.

The stellar obliquity is measured at approximately 39 degrees.

The planet's orbit is likely shaped by dynamical interactions.

Abstract

Warm Jupiters are close-in giant planets with relatively large planet-star separations (i.e., $10< a/R_\star <100$). Given their weak tidal interactions with their host stars, measurements of stellar obliquity may be used to probe the initial obliquity distribution and dynamical history for close-in gas giants. Using spectroscopic observations, we confirm the planetary nature of TOI-1859b and determine the stellar obliquity of TOI-1859 to be $\lambda = 38.9^{+2.8}_{-2.7}\deg$ relative to its planetary companion using the Rossiter-McLaughlin effect. TOI-1859b is a 64-day warm Jupiter orbiting around a late-F dwarf and has an orbital eccentricity of $0.57^{+0.12}_{-0.16}$, inferred purely from transit light curves. The eccentric and misaligned orbit of TOI-1859b is likely an outcome of dynamical interactions, such as planet-planet scattering and planet-disk resonance crossing.