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

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

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 Mb = 10.4 ± 0.9 M and Mc = 7.2 ± 1.4 M, which are low compared to most known planets of comparable radii. The RVs yield only an upper limit on Md (<5.8 M at 2σ). The RVs further reveal a fourth planet (e) with a minimum mass of 0.34 ± 0.01 MJup 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 ("i < 10°). We identify a second high-mass planet (f) with 95% confidence intervals on mass between 2 and 11 MJup 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.

Original languageEnglish (US)
Article number101
JournalAstronomical Journal
Volume163
Issue number2
DOIs
StatePublished - Feb 1 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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