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A HARPS-N mass for the elusive Kepler-37d : a case study in disentangling stellar activity and planetary signals
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(2021) A HARPS-N mass for the elusive Kepler-37d : a case study in disentangling stellar activity and planetary signals. Monthly Notices of the Royal Astronomical Society, 507 (2). pp. 1847-1868. doi:10.1093/mnras/stab2192
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Official URL: https://doi.org/10.1093/mnras/stab2192
Abstract
To date, only 18 exoplanets with radial velocity (RV) semi-amplitude <2 m s−1 have had their masses directly constrained. The biggest obstacle to RV detection of such exoplanets is variability intrinsic to stars themselves, e.g. nuisance signals arising from surface magnetic activity such as rotating spots and plages, which can drown out or even mimic planetary RV signals. We use Kepler-37 – known to host three transiting planets, one of which, Kepler-37d, should be on the cusp of RV detectability with modern spectrographs – as a case study in disentangling planetary and stellar activity signals. We show how two different statistical techniques – one seeking to identify activity signals in stellar spectra, and another to model activity signals in extracted RVs and activity indicators – can each enable a detection of the hitherto elusive Kepler-37d. Moreover, we show that these two approaches can be complementary, and in combination, facilitate a definitive detection and precise characterization of Kepler-37d. Its RV semi-amplitude of 1.22 ± 0.31 m s−1 (mass 5.4 ± 1.4 M⊕) is formally consistent with TOI-178b’s $1.05^{+0.25}_{-0.30}$ m s−1, the latter being the smallest detected RV signal of any transiting planet to date, though dynamical simulations suggest Kepler-37d’s mass may be on the lower end of our 1σ credible interval. Its consequent density is consistent with either a water-world or that of a gaseous envelope ($\sim 0.4{{\ \rm per\ cent}}$ by mass) surrounding a rocky core. Based on RV modelling and a re-analysis of Kepler-37 TTVs, we also suggest that the putative (non-transiting) planet Kepler-37e should be stripped of its ‘confirmed’ status.
| Item Type: | Journal Article | ||||||||||||||||||||||||||||||
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| Subjects: | Q Science > QB Astronomy | ||||||||||||||||||||||||||||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||||||||||||||||||||||
| SWORD Depositor: | Library Publications Router | ||||||||||||||||||||||||||||||
| Library of Congress Subject Headings (LCSH): | Extrasolar planets, Planets, Stars -- Clusters, Astrophysics | ||||||||||||||||||||||||||||||
| Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | ||||||||||||||||||||||||||||||
| Publisher: | Oxford University Press (OUP) | ||||||||||||||||||||||||||||||
| ISSN: | 1365-2966 | ||||||||||||||||||||||||||||||
| Official Date: | September 2021 | ||||||||||||||||||||||||||||||
| Dates: |
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| Volume: | 507 | ||||||||||||||||||||||||||||||
| Number: | 2 | ||||||||||||||||||||||||||||||
| Page Range: | pp. 1847-1868 | ||||||||||||||||||||||||||||||
| DOI: | 10.1093/mnras/stab2192 | ||||||||||||||||||||||||||||||
| Status: | Peer Reviewed | ||||||||||||||||||||||||||||||
| Publication Status: | Published | ||||||||||||||||||||||||||||||
| Reuse Statement (publisher, data, author rights): | This is a pre-copyedited, author-produced version of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record V M Rajpaul, L A Buchhave, G Lacedelli, K Rice, A Mortier, L Malavolta, S Aigrain, L Borsato, A W Mayo, D Charbonneau, M Damasso, X Dumusque, A Ghedina, D W Latham, M López-Morales, A Magazzù, G Micela, E Molinari, F Pepe, G Piotto, E Poretti, S Rowther, A Sozzetti, S Udry, C A Watson, A HARPS-N mass for the elusive Kepler-37d: a case study in disentangling stellar activity and planetary signals, Monthly Notices of the Royal Astronomical Society, Volume 507, Issue 2, October 2021, Pages 1847–1868 is available online at: https://doi.org/10.1093/mnras/stab2192 | ||||||||||||||||||||||||||||||
| Access rights to Published version: | Restricted or Subscription Access | ||||||||||||||||||||||||||||||
| RIOXX Funder/Project Grant: |
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