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

Polanski, Alex S. and Crossfield, Ian J. M. and Burt, Jennifer A. and Nowak, Grzegorz and López-Morales, Mercedes and Mortier, Annelies and Poretti, Ennio and Behmard, Aida and Benneke, Björn and Blunt, Sarah and Bonomo, Aldo S. and Butler, R. Paul and Chontos, Ashley and Cosentino, Rosario and Crane, Jeffrey D. and Dumusque, Xavier and Fulton, Benjamin J. and Ghedina, Adriano and Gorjian, Varoujan and Grunblatt, Samuel K. and Harutyunyan, Avet and Howard, Andrew W. and Isaacson, Howard and Kosiarek, Molly R. and Latham, David W. and Luque, Rafael and Martinez Fiorenzano, Aldo F. and Mayor, Michel and Mills, Sean M. and Molinari, Emilio and Nagel, Evangelos and Palle, Enric and Petigura, Erik A. and Shectman, Stephen A. and Sozzetti, Alessandro and Teske, Johanna K. and Wang, Sharon Xuesong and Weiss, Lauren M. (2021) Wolf 503 b: Characterization of a Sub-Neptune Orbiting a Metal-poor K Dwarf. Astronomical Journal, 162 (6). Art. No. 238. ISSN 0004-6256. doi:10.3847/1538-3881/ac1590.

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Using radial-velocity measurements from four instruments, we report the mass and density of a 2.043 ±0.069 R_⊕ 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 ± 0.05. 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)M_⊕ , in combination with the updated radius measurements, gives Wolf 503 b a bulk density of ρ = 2.92^(+0.50)_(-0.44) g cm⁻³. Using interior composition models, we find this density is consistent with an Earth-like core with either a substantial H₂O mass fraction (45^(+19)_(-16)%) or a modest H/He envelope (0.5% ± 0.3%). The low H/He mass fraction, along with the old age of Wolf 503 (11 ± 2 Gyr), 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.

Item Type:Article
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URLURL TypeDescription Paper
Polanski, Alex S.0000-0001-7047-8681
Crossfield, Ian J. M.0000-0002-1835-1891
Burt, Jennifer A.0000-0002-0040-6815
Nowak, Grzegorz0000-0002-7031-7754
López-Morales, Mercedes0000-0003-3204-8183
Mortier, Annelies0000-0001-7254-4363
Poretti, Ennio0000-0003-1200-0473
Behmard, Aida0000-0003-0012-9093
Benneke, Björn0000-0001-5578-1498
Blunt, Sarah0000-0002-3199-2888
Bonomo, Aldo S.0000-0002-6177-198X
Butler, R. Paul0000-0003-1305-3761
Chontos, Ashley0000-0003-1125-2564
Cosentino, Rosario0000-0003-1784-1431
Crane, Jeffrey D.0000-0002-5226-787X
Dumusque, Xavier0000-0002-9332-2011
Fulton, Benjamin J.0000-0003-3504-5316
Ghedina, Adriano0000-0003-4702-5152
Gorjian, Varoujan0000-0002-8990-2101
Grunblatt, Samuel K.0000-0003-4976-9980
Howard, Andrew W.0000-0001-8638-0320
Isaacson, Howard0000-0002-0531-1073
Kosiarek, Molly R.0000-0002-6115-4359
Latham, David W.0000-0001-9911-7388
Luque, Rafael0000-0002-4671-2957
Martinez Fiorenzano, Aldo F.0000-0002-4272-4272
Mayor, Michel0000-0002-9352-5935
Mills, Sean M.0000-0002-4535-6241
Molinari, Emilio0000-0002-1742-7735
Nagel, Evangelos0000-0002-4019-3631
Palle, Enric0000-0003-0987-1593
Petigura, Erik A.0000-0003-0967-2893
Shectman, Stephen A.0000-0002-8681-6136
Sozzetti, Alessandro0000-0002-7504-365X
Wang, Sharon Xuesong0000-0002-6937-9034
Weiss, Lauren M.0000-0002-3725-3058
Additional Information:© 2021. The American Astronomical Society. Received 2021 February 24; revised 2021 July 14; accepted 2021 July 15; published 2021 November 11. The authors thank the anonymous referee whose thorough review greatly increased the quality of this publication. We also thank the time assignment committees of the University of California, the California Institute of Technology, NASA, and the University of Hawaii for supporting the TESS-Keck Survey with observing time at Keck Observatory and on the Automated Planet Finder. We thank NASA for funding associated with our Key Strategic Mission Support project. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff for support of HIRES and remote observing. We recognize and acknowledge the cultural role and reverence that the summit of Maunakea has within the indigenous Hawaiian community. We are deeply grateful to have the opportunity to conduct observations from this mountain. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundacion Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. The HARPS-N project has been funded by the Prodex Program of the Swiss Space Office (SSO), the Harvard University Origins of Life Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), and the Italian National Astrophysical Institute (INAF), the University of St Andrews, Queen's University Belfast, and the University of Edinburgh. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA) This work is based in part on observations made with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. A.M. acknowledges support from the senior Kavli Institute Fellowships. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement SCORE No. 851555). This research made use of Lightkurve, a Python package for Kepler and TESS data analysis (Lightkurve Collaboration et al.2018). Facilities: Keck:I (HIRES) - KECK I Telescope, Magellan:Clay (PFS) - , Observatorio del Roque de los Muchachos:TNG (HARPS-N) - , Calar Alto:Zeiss 3.5m (CARMENES) - , Spitzer. - Software: exoplanet (Foreman-Mackey et al. 2021), radvel (Fulton et al. 2018), Lightkurve (Lightkurve Collaboration et al. 2018), batman (Kreidberg 2015), isoclassify (Huber et al. 2017), emcee (Foreman-Mackey et al. 2013), PandExo (Batalha et al. 2017), ExoTransmit (Kempton et al. 2017), smint (Piaulet et al. 2021).
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Swiss Space Office (SSO)UNSPECIFIED
Harvard University Origin of Life Initiative (HUOLI)UNSPECIFIED
Scottish Universities Physics AllianceUNSPECIFIED
University of GenevaUNSPECIFIED
Smithsonian Astrophysical ObservatoryUNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
University of St. AndrewsUNSPECIFIED
Queen's University BelfastUNSPECIFIED
University of EdinburghUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Kavli Institute for CosmologyUNSPECIFIED
European Research Council (ERC)851555
Subject Keywords:Exoplanet astronomy; Radial velocity; Transit photometry; Extrasolar gaseous planets; Ephemerides; K dwarf stars
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486); Radial velocity (1332); Transit photometry (1709); Extrasolar gaseous planets (2172); Ephemerides (464); K dwarf stars (876)
Record Number:CaltechAUTHORS:20211018-185226948
Persistent URL:
Official Citation:Alex S. Polanski et al 2021 AJ 162 238
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111520
Deposited By: George Porter
Deposited On:19 Oct 2021 15:20
Last Modified:12 Nov 2021 21:11

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