The NEID Earth Twin Survey. IV. Confirming an 89 days, m sin i = 10 M_⊕ Planet Orbiting a Nearby Sun-like Star

We present the confirmation of HD 190360 d, a warm (P = 88.69 0_−0.049^+0.051 days), low-mass (m sin i = 10.2 3_−0.80^+0.81 M ⊕) planet orbiting the nearby (d = 16.0 pc), Sun-like (G7) star HD 190360. We detect HD 190360 d at high statistical significance even though its radial velocity (RV) semiamplitude is only K = 1.48 ± 0.11 m s⁻¹. Such low-amplitude signals are often challenging to confirm due to potential confusion with low-amplitude stellar signals. The HD 190360 system previously had two known planets: the 1.7 M_J (true mass) HD 190360 b on a 7.9 yr orbit and the 21 M_⊕(minimum mass) HD 190360 c on a 17.1 days orbit. Here, we present an in-depth analysis of the HD 190360 planetary system that comprises more than 30 yr of RV measurements and absolute astrometry from the Hipparcos and Gaia spacecraft. Our analysis uses more than 1400 RVs, including nearly 100 from NEID. The proper motion anomaly as measured by these two astrometric missions solves for the dynamical mass of HD 190360 b and contributes to our understanding of the overall system architecture, while the long baseline of RVs enables the robust characterization of HD 190360 c and confirms the discovery of HD 190360 d.