Three’s Company: An Additional Non-transiting Super-Earth in the Bright HD 3167 System, and Masses for All Three Planets
Henning, Thomas; Butler, R. Paul; Vogt, Steven S.; Vanderburg, Andrew; López-Morales, Mercedes; Batalha, Natasha E.; Latham, David W.; Knutson, Heather A.; Schlieder, Joshua E.; Isaacson, Howard T.; Howard, Andrew W.; Crossfield, Ian J. M.; Kosiarek, Molly; Weiss, Lauren M.; Holden, Bradford P.; Buchhave, Lars A.; Dupuy, Trent J.; Ciardi, David R.; Udry, Stéphane; Johnson, John A.; Burt, Jennifer; Barman, Travis S.; Hansen, Brad M. S.; Piotto, Giampaolo; Watson, Christopher A.; Bouchy, François; Batygin, Konstantin; Charbonneau, David; Sinukoff, Evan; Pepe, Francesco; Brewer, John M.; Benneke, Björn; Christiansen, Jessie L.; Lovis, Christophe; Sasselov, Dimitar; Sozzetti, Alessandro; Greene, Thomas P.; Dressing, Courtney; Ehrenreich, David; Rice, Ken; Mortier, Annelies; Cosentino, Rosario; Mayor, Michel; Molinari, Emilio; Fulton, B. J.; Thompson, Susan E.; Ségransan, Damien; Coughlin, Jeffrey L.; Mullally, Fergal; Phillips, David F.; Micela, Giuseppina; Hirsch, Lea; Collier Cameron, Andrew; Rogers, Leslie A.; Malavolta, Luca; Fiorenzano, Aldo; Motalebi, Fatemeh; Petigura, Erik
United States, United Kingdom, Italy, Spain, Switzerland, Denmark, Germany, Canada
Abstract
HD 3167 is a bright (V = 8.9), nearby K0 star observed by the NASA K2 mission (EPIC 220383386), hosting two small, short-period transiting planets. Here we present the results of a multi-site, multi-instrument radial-velocity campaign to characterize the HD 3167 system. The masses of the transiting planets are 5.02 ± 0.38 {M}\oplus for HD 3167 b, a hot super-Earth with a likely rocky composition ({ρ }b = {5.60}-1.43+2.15 g cm-3), and {9.80}-1.24+1.30 {M}\oplus for HD 3167 c, a warm sub-Neptune with a likely substantial volatile complement ({ρ }c = {1.97}-0.59+0.94 g cm-3). We explore the possibility of atmospheric composition analysis and determine that planet c is amenable to transmission spectroscopy measurements, and planet b is a potential thermal emission target. We detect a third, non-transiting planet, HD 3167 d, with a period of 8.509 ± 0.045 d (between planets b and c) and a minimum mass of 6.90 ± 0.71 {M}\oplus . We are able to constrain the mutual inclination of planet d with planets b and c: we rule out mutual inclinations below 1.°3 because we do not observe transits of planet d. From 1.°3 to 40°, there are viewing geometries invoking special nodal configurations, which result in planet d not transiting some fraction of the time. From 40° to 60°, Kozai-Lidov oscillations increase the system’s instability, but it can remain stable for up to 100 Myr. Above 60°, the system is unstable. HD 3167 promises to be a fruitful system for further study and a preview of the many exciting systems expected from the upcoming NASA TESS mission.