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

Warm Jupiters are close-in giant planets with relatively large planet-star separations (i.e., $10<a\mathrm{/}{R}_{\star }<100$). 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 $\lambda =38.9_{-2.7}^{+2.8}\mathrm{°}$ 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 $0.57_{-0.16}^{+0.12}$, 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.