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

• Published in: The Astronomical journal 2022-02, Vol.163 (2), p.101
• Main Authors: Lubin, Jack, Van Zandt, Judah, Holcomb, Rae, Weiss, Lauren M., Petigura, Erik A, Robertson, Paul, Akana Murphy, Joseph M., Scarsdale, Nicholas, Batygin, Konstantin, Polanski, Alex S., Batalha, Natalie M., Crossfield, Ian J. M., Dressing, Courtney, Fulton, Benjamin, Howard, Andrew W., Huber, Daniel, Isaacson, Howard, Kane, Stephen R., Roy, Arpita, Beard, Corey, Blunt, Sarah, Chontos, Ashley, Dai, Fei, Dalba, Paul A., Gary, Kaz, Giacalone, Steven, Hill, Michelle L., Mayo, Andrew, Močnik, Teo, Kosiarek, Molly R., Rice, Malena, Rubenzahl, Ryan A., Latham, David W., Seager, S., Winn, Joshua N.
• Format: Article
• Language: English
• Subjects: Astrometry; Astronomy; Astrophysics; Confidence intervals; Exoplanet astronomy; Exoplanet dynamics; Extrasolar planets; Orbits; Radial velocity; Transit
• ISSN: 0004-6256; 1538-3881
• DOI: 10.3847/1538-3881/ac3d38

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 (