HD 191939: Three Sub-Neptunes Transiting a Sun-like Star Only 54 pc Away

Badenas-Agusti, Mariona; Günther, Maximilian N.; Daylan, Tansu; Mikal-Evans, Thomas; Vanderburg, Andrew; Huang, Chelsea X.; Matthews, Elisabeth; Rackham, Benjamin V.; Bieryla, Allyson; Stassun, Keivan G.; Kane, Stephen R.; Shporer, Avi; Fulton, Benjamin J.; Hill, Michelle L.; Nowak, Grzegorz; Ribas, Ignasi; Pallé, Enric; Jenkins, Jon M.; Latham, David W.; Seager, Sara; Ricker, George R.; Vanderspek, Roland K.; Winn, Joshua N.; Abril-Pla, Oriol; Collins, Karen A.; Serra, Pere Guerra; Niraula, Prajwal; Rustamkulov, Zafar; Barclay, Thomas; Crossfield, Ian J. M.; Howell, Steve B.; Ciardi, David R.; Gonzales, Erica J.; Schlieder, Joshua E.; Caldwell, Douglas A.; Fausnaugh, Michael; McDermott, Scott; Paegert, Martin; Pepper, Joshua; Rose, Mark E.; Twicken, Joseph D.
Bibliographical reference

The Astronomical Journal

Advertised on:
9
2020
Number of authors
41
IAC number of authors
2
Citations
16
Refereed citations
15
Description
We present the discovery of three sub-Neptune-sized planets transiting the nearby and bright Sun-like star HD 191939 (TIC 269701147, TOI 1339), a Ks = 7.18 mag G8 V dwarf at a distance of only 54 pc. We validate the planetary nature of the transit signals by combining 5 months of data from the Transiting Exoplanet Survey Satellite with follow-up ground-based photometry, archival optical images, radial velocities, and high angular resolution observations. The three sub-Neptunes have similar radii ( ${R}_{{\rm{b}}}={3.42}_{-0.11}^{+0.11}$ , ${R}_{{\rm{c}}}={3.23}_{-0.11}^{+0.11}$ , and ${R}_{{\rm{d}}}={3.16}_{-0.11}^{+0.11}\,{R}_{\oplus }$ ), and their orbits are consistent with a stable, circular, and coplanar architecture near mean-motion resonances of 1:3 and 3:4 (Pb = 8.88, Pc = 28.58, and Pd = 38.35 days). The HD 191939 system is an excellent candidate for precise mass determinations of the planets with high-resolution spectroscopy due to the host star's brightness and low chromospheric activity. Moreover, the system's compact and near-resonant nature can provide an independent way to measure planetary masses via transit timing variations while also enabling dynamical and evolutionary studies. Finally, as a promising target for multiwavelength transmission spectroscopy of all three planets' atmospheres, HD 191939 can offer valuable insight into multiple sub-Neptunes born from a protoplanetary disk that may have resembled that of the early Sun.
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Exoplanets and Astrobiology

The search for life in the universe has been driven by recent discoveries of planets around other stars (known as exoplanets), becoming one of the most active fields in modern astrophysics. The growing number of new exoplanets discovered in recent years and the recent advance on the study of their atmospheres are not only providing new valuable

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