TESS-Keck Survey. IX. Masses of Three Sub-Neptunes Orbiting HD 191939 and the Discovery of a Warm Jovian plus a Distant Substellar Companion

Jack Lubin, Judah Van Zandt, Rae Holcomb, Lauren M. Weiss, Erik A Petigura, Paul Robertson, Joseph M. Akana Murphy, Nicholas Scarsdale, Konstantin Batygin, Alex S. Polanski, Natalie M. Batalha, Ian J. M. Crossfield (+24 others)
2022 Astronomical Journal  
Exoplanet systems with multiple transiting planets are natural laboratories for testing planetary astrophysics. One such system is HD 191939 (TOI 1339), a bright (V = 9) and Sun-like (G9V) star, which TESS found to host three transiting planets (b, c, and d). The planets have periods of 9, 29, and 38 days each with similar sizes from 3 to 3.4 R ⊕. To further characterize the system, we measured the radial velocity (RV) of HD 191939 over 415 days with Keck/HIRES and APF/Levy. We find that M b =
more » ... 0.4 ± 0.9 M ⊕ and M c = 7.2 ± 1.4 M ⊕, which are low compared to most known planets of comparable radii. The RVs yield only an upper limit on M d (<5.8 M ⊕ at 2σ). The RVs further reveal a fourth planet (e) with a minimum mass of 0.34 ± 0.01 M Jup and an orbital period of 101.4 ± 0.4 days. Despite its nontransiting geometry, secular interactions between planet e and the inner transiting planets indicate that planet e is coplanar with the transiting planets (Δi < 10°). We identify a second high-mass planet (f) with 95% confidence intervals on mass between 2 and 11 M Jup and period between 1700 and 7200 days, based on a joint analysis of RVs and astrometry from Gaia and Hipparcos. As a bright star hosting multiple planets with well-measured masses, HD 191939 presents many options for comparative planetary astronomy, including characterization with JWST.
doi:10.3847/1538-3881/ac3d38 fatcat:lnqj5n4gajh25a7tpv4kaxcsiy