Wolf 503 b: Characterization of a Sub-Neptune Orbiting a Metal-Poor K Dwarf

• Published in: arXiv.org
• Main Authors: Polanski, Alex S, Crossfield, Ian J M, Burt, Jennifer A, Nowak, Grzegorz, López-Morales, Mercedes, Mortier, Annelies, Poretti, Ennio, Behmard, Aida, Benneke, Björn, Blunt, Sarah, Bonomo, Aldo S, Butler, R Paul, Chontos, Ashley, Cosentino, Rosario, Crane, Jeffrey D, Dumusque, Xavier, Fulton, Benjamin J, Ghedina, Adriano, Gorjian, Varoujan, Grunblatt, Samuel K, Harutyunyan, Avet, Howard, Andrew W, Isaacson, Howard, Kosiarek, Molly R, Latham, David W, Luque, Rafael, Martinez Fiorenzano, Aldo F, Mayor, Michel, Mills, Sean M, Molinari, Emilio, Nagel, Evangelos, Pallé, Enric, Petigura, Erik A, Shectman, Stephen A, Sozzetti, Alessandro, Teske, Johanna K, Sharon Xuesong Wang, Weiss, Lauren M
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 16.07.2021
• Subjects: Bulk density; Physics - Earth and Planetary Astrophysics; Radial velocity; Transit
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2107.08092

Using radial velocity measurements from four instruments, we report the mass and density of a \(2.043\pm0.069 ~\rm{R}_{\oplus}\) sub-Neptune orbiting the quiet K-dwarf Wolf 503 (HIP 67285). In addition, we present improved orbital and transit parameters by analyzing previously unused short-cadence \(K2\) campaign 17 photometry and conduct a joint radial velocity-transit fit to constrain the eccentricity at \(0.41\pm0.05\). The addition of a transit observation by \(Spitzer\) also allows us to refine the orbital ephemeris in anticipation of further follow-up. Our mass determination, \(6.26^{+0.69}_{-0.70}~\rm{M}_{\odot}\), in combination with the updated radius measurements, gives Wolf 503 b a bulk density of \(\rho = 2.92\pm ^{+0.50}_{-0.44}\) \(\rm{g}~\rm{cm}^{-3}\). Using interior composition models, we find this density is consistent with an Earth-like core with either a substantial \(\rm{H}_2\rm{O}\) mass fraction (\(45^{+19.12}_{-16.15}\%\)) or a modest H/He envelope (\(0.5\pm0.28\%\)). The low H/He mass fraction, along with the old age of Wolf 503 (\(11\pm2\) Gyrs), makes this sub-Neptune an opportune subject for testing theories of XUV-driven mass loss while the brightness of its host (\(J=8.3\) mag) makes it an attractive target for transmission spectroscopy.