Abstract
Super-Earths belong to a class of planet not found in the Solar system, but which appear common in the Galaxy. Given that some super-Earths are rocky, while others retain substantial atmospheres, their study can provide clues as to the formation of both rocky and gaseous planets, and - in particular - they can help to constrain the role of photoevaporation in sculpting the exoplanet population. GJ 9827 is a system already known to host three super-Earths with orbital periods of 1.2, 3.6, and 6.2 d. Here, we use new HARPS-N radial velocity measurements, together with previously published radial velocities, to better constrain the properties of the GJ 9827 planets. Our analysis cannot place a strong constraint on the mass of GJ 9827 c, but does indicate that GJ 9827 b is rocky with a composition that is probably similar to that of the Earth, while GJ 9827 d almost certainly retains a volatile envelope. Therefore, GJ 9827 hosts planets on either side of the radius gap that appears to divide super-Earths into pre-dominantly rocky ones that have radii below ∼1.5R ⊕, and ones that still retain a substantial atmosphere and/or volatile components, and have radii above ∼2R ⊕. That the less heavily irradiated of the three planets still retains an atmosphere, may indicate that photoevaporation has played a key role in the evolution of the planets in this system.
Original language | English |
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Pages (from-to) | 3731-3745 |
Number of pages | 15 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 484 |
Issue number | 3 |
DOIs | |
Publication status | Published - 11 Apr 2019 |
Bibliographical note
Funding Information:LM and DM acknowledge support from INAF/Frontiera through the ‘Progetti Premiali’ funding scheme of the Italian Ministry of Education, University, and Research. Some of this work has been carried out within the framework of the NCCR PlanetS, supported by the Swiss National Science Foundation. AV is supported by the NSF Graduate Research Fellowship, grant number DGE 1144152. This work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute (AV and RDH). ACC acknowledges support from STFC consolidated grant number ST/M001296/1. DWL acknowledges partial support from the Kepler mission under NASA Cooperative Agreement NNX13AB58A with the Smithsonian Astrophysical Observatory. CAW acknowledges support by STFC grant ST/P000312/1. XD is grateful to the Society in Science-Branco Weiss Fellowship for its financial support. This material is based upon work supported by the National Aeronautics and Space Administration under grants numbers NNX15AC90G and NNX17AB59G issued through the Exoplanets Research Program. This publication was made possible through the support of a grant from the John Templeton Foundation. The opinions expressed are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. The HARPS-N project has been funded by the Prodex Program of the Swiss Space Office, the Harvard University Origins of Life Initiative, the Scottish Universities Physics Alliance, the University of Geneva, the Smithsonian Astrophysical Observatory, and the Italian National Astrophysical Institute, the University of St Andrews, Queen’s University Belfast, and the University of Edinburgh. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5–26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. This research has made use of NASA’s Astrophysics Data System and the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.
Publisher Copyright:
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
Keywords
- planets and satellites: composition
- planets and satellites: detection
- planets and satellites: fundamental parameters
- planets and satellites: general
- Stars: individual: GJ 9827 (2MASS J23270480-0117108, EPIC 246389858, HIP 115752)
- techniques: radial velocities
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science