The CARMENES search for exoplanets around M dwarfs: characterization of the nearby ultra-compact multiplanetary system YZ Ceti

dc.contributor.authorCaballero, J. A.
dc.contributor.authorCortés Contreras, Miriam
dc.contributor.authorDíez Alonso, Enrique
dc.contributor.authorDomínguez Fernández, A.J.
dc.contributor.authorMontes Gutiérrez, David
dc.description© ESO 2020. Artículo firmado por 41 autores. This work was supported by the DFG Research Unit FOR2544 “Blue Planets around Red Stars”, project no. RE 2694 / 4-1. CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almería, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERF FICTS – 2011 – 02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l’Espai, Insitut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano - Alemán), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. The authors acknowledge support by the High Performance and Cloud Computing Group at the Zentrum für Datenverarbeitung of the University of Tübingen, the state of Baden-Württemberg through bwHPC and the German Research Foundation (DFG) through grant no. INST 37 / 935 – 1 FUGG. We acknowledge financial support from the Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades and the European FEDER/ERF funds through projects AYA2015-69350-C3-2-P, AYA2016-79425- C3-1/2/3-P, ESP2017-87676-C5-2-R, ESP2017-87143-R and the Centre of Excellence “Severo Ochoa” and “María de Maeztu” awards to the Instituto de Astrofísica de Canarias (SEV-2015-0548), Instituto de Astrofísica de Andalucía (SEV-2017-0709), and Centro de Astrobiología (MDM-2017-0737), and the Generalitat de Catalunya/CERCA programme. This work is supported by the Science and Technology Facilities Council [ST/M001008/1 and ST/P000584/1]. J.S.J. acknowledges support by Fondecyt grant 1161218 and partial support by CATA-Basal (PB06, CONICYT). Z.M.B acknowledges funds from CONICYTFONDECYT/Chile Postdoctorado 3180405. M.H.L. was supported in part by Hong Kong RGC grant HKU 17305618. T.H. acknowledges support from the European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins 83 24 28. Data were partly collected with the robotic 40-cm telescope ASH2 at the SPACEOBS observatory (San Pedro de Atacama, Chile) and the 90-cm telescope at Sierra Nevada Observatory (Granada, Spain) both operated by the Instituto de Astrofífica de Andalucía (IAA). This work has made use of the Exo-Striker tool (Trifonov 2019).
dc.description.abstractContext. The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets, and a fourth tentative signal. The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data. The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters. Aims. With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues. Methods. We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases. We discuss additional signals in the RV data, and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model. To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits. Results. We find no evidence for a fourth possible companion. We resolve the aliases: the three planets orbit the star with periods of 2.02 d, 3.06 d, and 4.66 d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters, in particular the eccentricity of the innermost planet. Using photometry we determine the stellar rotational period to be close to 68 d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators. From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is i_(min) = 0.9 deg. From the absence of a transit event with TESS, we derive an upper limit of the inclination of i_(max) = 87.43 deg. Conclusions. YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets. Additionally, stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system. Stability considerations then allow additional constraints to be placed on the planetary parameters.
dc.description.departmentDepto. de Física de la Tierra y Astrofísica
dc.description.facultyFac. de Ciencias Físicas
dc.description.sponsorshipUnión Europea. Horizonte 2020
dc.description.sponsorshipDFG Research Unit FOR2544 “Blue Planets around Red Stars”
dc.description.sponsorshipMinisterio de Ciencia e Innovación (MICINN)/FEDER
dc.description.sponsorshipCentro de Excelencia Severo Ochoa
dc.description.sponsorshipUnidad de Excelencia Maria de Maeztu
dc.description.sponsorshipGerman Max-Planck-Gesellschaft (MPG)
dc.description.sponsorshipConsejo Superior de Investigaciones Científicas (CSIC)
dc.description.sponsorshipMax-Planck-Institut für Astronomie
dc.description.sponsorshipInstituto de Astrofísica de Andalucía
dc.description.sponsorshipLandessternwarte Königstuhl
dc.description.sponsorshipInstitut de Ciències de l’Espai
dc.description.sponsorshipInsitut für Astrophysik Göttingen
dc.description.sponsorshipThüringer Landessternwarte Tautenburg
dc.description.sponsorshipInstituto de Astrofísica de Canarias
dc.description.sponsorshipHamburger Sternwarte
dc.description.sponsorshipCentro de Astrobiología and Centro Astronómico Hispano - Alemán
dc.description.sponsorshipthe German Science Foundation through the Major Research Instrumentation Programme
dc.description.sponsorshipDFG Research Unit FOR2544 “Blue Planets around Red Stars”
dc.description.sponsorshipthe Klaus Tschira Stiftung
dc.description.sponsorshipthe states of Baden-Württemberg and Niedersachsen
dc.description.sponsorshipJunta de Andalucía, Spain
dc.description.sponsorshipHigh Performance and Cloud Computing Group at the Zentrum für Datenverarbeitung of the University of Tübingen
dc.description.sponsorshipthe state of Baden-Württemberg through bwHPC
dc.description.sponsorshipthe German Research Foundation (DFG)
dc.description.sponsorshipAgencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades , Spain
dc.description.sponsorshipCentro de Astrobiología
dc.description.sponsorshipInstituto de Astrofísica de Andalucía, Spain
dc.description.sponsorshipthe Generalitat de Catalunya/CERCA programme
dc.description.sponsorshipthe Science and Technology Facilities Council
dc.description.sponsorshipCONICYTFONDECYT/Chile Postdoctorado
dc.description.sponsorshipHong Kong RGC
dc.journal.titleAstronomy & Astrophysics
dc.publisherEDP Sciencies
dc.relation.projectIDOrigins (832428)
dc.relation.projectID(AYA2015-69350-C3-2-P, AYA2016-79425- C3-1/2/3-P, ESP2017-87676-C5-2-R, ESP2017-87143-R)
dc.relation.projectIDRE 2694 / 4-1
dc.relation.projectID(SEV-2015-0548; SEV-2017-0709)
dc.relation.projectIDFICTS – 2011 – 02
dc.relation.projectIDINST 37 / 935 – 1 FUGG
dc.relation.projectIDPB06, CONICYT
dc.relation.projectIDHKU 17305618
dc.rights.accessRightsopen access
dc.subject.ucmAstronomía (Física)
dc.titleThe CARMENES search for exoplanets around M dwarfs: characterization of the nearby ultra-compact multiplanetary system YZ Ceti
dc.typejournal article
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