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An estimate of the k2 Love number of WASP-18Ab from its radial velocity measurements

Csizmadia, Sz. and Hellard, H. and Smith, A. M. S. (2019) An estimate of the k2 Love number of WASP-18Ab from its radial velocity measurements. Astronomy and Astrophysics, 623, A45. EDP Sciences. ISSN 0004-6361

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Official URL: http://dx.doi.org/10.1051/0004-6361/201834376

Abstract

Context. Increasing our knowledge of the interior structure, composition, and density distribution of exoplanets is crucial to make progress in the understanding of exoplanetary formation, migration and habitability. However, the directly measurable mass and radius values offer little constraint on interior structure, because the inverse problem is highly degenerate. Therefore, there is a clear need for a third observable of exoplanet interiors. This third observable can be the k2 fluid Love number which measures the central mass concentration of an exoplanet. Aims: The aims of this paper are (i) to develop a basic model to fit the long-term radial velocity and TTV variations caused by tidal interactions, (ii) to apply the model to the WASP-18Ab system, and (iii) to estimate the Love number of the planet. Methods: Archival radial velocity, transit and occultation timing data were collected and fitted using the model introduced here. Results: The best model fit to the archival radial velocity and timing data of WASP-18Ab was obtained with a Love number of the massive ( 10 MJup) hot Jupiter WASP-18Ab: k2,Love = 0.62-0.19+0.55. This causes apsidal motion in the system, at a rate of 0.0087 ± 0.0033°/days ≊ 31.3 ± 11.8 arcsec day-1. When checking possible causes of periastron precession, other than the relativistic term or the non-spherical shape of the components, we found a companion star to the WASP-18 system, named WASP-18B which is a probable M6.5V dwarf with 0.1 M☉ at 3519 AU distance from the transit host star. We also find that small orbital eccentricities may be real, rather than an apparent effect caused by the non-spherical stellar shape.

Item URL in elib:https://elib.dlr.de/127759/
Document Type:Article
Title:An estimate of the k2 Love number of WASP-18Ab from its radial velocity measurements
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Csizmadia, Sz.szilard.csizmadia (at) dlr.dehttps://orcid.org/0000-0001-6803-9698
Hellard, H.hugo.hellard (at) dlr.dehttps://orcid.org/0000-0003-0077-3196
Smith, A. M. S.alexis.smith (at) dlr.dehttps://orcid.org/0000-0002-2386-4341
Date:March 2019
Journal or Publication Title:Astronomy and Astrophysics
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:623
Page Range:A45
Editors:
EditorsEmail
Forveille, ThierryUNSPECIFIED
Publisher:EDP Sciences
ISSN:0004-6361
Status:Published
Keywords:techniques: radial velocities; planets and satellites: interiors; planets and satellites: individual: WASP-18b; methods: data analysis; Astrophysics - Earth and Planetary Astrophysics
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Project PLATO
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Extrasolar Planets and Atmospheres
Deposited By: Csizmadia, Szilard
Deposited On:13 Jun 2019 10:12
Last Modified:31 Jul 2019 20:25

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