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

2022; Institute of Physics; Volume: 163; Issue: 2 Linguagem: Inglês

10.3847/1538-3881/ac3d38

1538-3881

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, Courtney D. Dressing, Benjamin J. Fulton, Andrew W. Howard, Daniel Huber, Howard Isaacson, Stephen R. Kane, Arpita Roy, Corey Beard, Sarah Blunt, Ashley Chontos, Fei Dai, Paul A. Dalba, Kaz Gary, Steven Giacalone, Michelle L. Hill, Andrew W. Mayo, Teo Močnik, Molly Kosiarek, Malena Rice, Ryan A. Rubenzahl, David W. Latham, Sara Seager, Joshua N. Winn, Kaz Gary,

Astrophysics and Star Formation Studies

Abstract 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 = 10.4 ± 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 2 σ ). 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 (Δ i < 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.