TOI-1670 c, a 40 day Orbital Period Warm Jupiter in a Compact System, Is Well Aligned

We report the measurement of the sky-projected obliquity angle lambda of the warm Jovian exoplanet TOI-1670 c via the Rossiter-McLaughlin effect. We observed the transit window during UT 2023 April 20 for 7 continuous hours with NEID on the 3.5 m WIYN Telescope at Kitt Peak National Observatory. TOI-1670 hosts a sub-Neptune (P similar to 11 days; planet b) interior to the warm Jovian (P similar to 40 days; planet c), which presents an opportunity to investigate the dynamics of a warm Jupiter with an inner companion. Additionally, TOI-1670 c is now among the longest-period planets to date to have its sky-projected obliquity angle measured. We find planet c is well aligned to the host star, with lambda = - 0.degrees 3 +/- 2.degrees 2. TOI-1670 c joins a growing census of aligned warm Jupiters around single stars and aligned planets in multiplanet systems.