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dc.rights.license© ESO 2021-
dc.contributor.authorHeeren, P.-
dc.contributor.authorReffert, S.-
dc.contributor.authorTrifonov, T.-
dc.contributor.authorWong, K. H.-
dc.contributor.authorHoi Lee, M.-
dc.contributor.authorLillo Box, J.-
dc.contributor.authorQuirrenbach, A.-
dc.contributor.authorArentoft, T.-
dc.contributor.authorAlbrecht, S.-
dc.contributor.authorGrundahl, F.-
dc.contributor.authorFredslund Andersen, M.-
dc.contributor.authorAntoci, V.-
dc.contributor.authorPallé, P. L.-
dc.contributor.otherUnidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737-
dc.date.accessioned2022-02-15T14:12:35Z-
dc.date.available2022-02-15T14:12:35Z-
dc.date.issued2021-03-29-
dc.identifier.citationAstronomy and Astrophysics 647: A160(2021)es
dc.identifier.issn0004-6361-
dc.identifier.otherhttps://www.aanda.org/articles/aa/abs/2021/03/aa40087-20/aa40087-20.html-
dc.identifier.urihttp://hdl.handle.net/20.500.12666/572-
dc.descriptionRV data (Tables A.1 and A.2) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/647/A160 Based on observations collected at the Lick Observatory, University of California. Based on observations collected with the Hertzsprung SONG telescope at the Spanish Observatorio del Teide, Tenerife. Based on data collected by the BRITE Constellation satellite mission, designed, built, launched, operated, and supported by the Austrian Research Promotion Agency (FFG), the University of Vienna, the Technical University of Graz, the University of Innsbruck, the Canadian Space Agency (CSA), the University of Toronto Institute for Aerospace Studies (UTIAS), the Foundation for Polish Science & Technology (FNiTP MNiSW), and National Science Centre (NCN). a Fellow of the International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD).es
dc.description.abstractContext. Using the Hamilton Échelle Spectrograph at Lick Observatory, we have obtained precise radial velocities (RVs) of a sample of 373 G- and K-giant stars over more than 12 yr, leading to the discovery of several single and multiple planetary systems. The RVs of the long-period (~53 yr) spectroscopic binary ε Cyg (HIP 102488) are found to exhibit additional regular variations with a much shorter period (~291 days). Aims. We intend to improve the orbital solution of the ε Cyg system and attempt to identify the cause of the nearly periodic shorter period variations, which might be due to an additional substellar companion. Methods. We used precise RV measurements of the K-giant star ε Cyg from Lick Observatory, in combination with a large set of RVs collected more recently with the SONG telescope, as well as archival data sets. We fit Keplerian and fully dynamical N-body models to the RVs in order to explore the properties of a previously known spectroscopic stellar companion and to investigate whether there is an additional planetary companion in the system. To search for long-term stable regions in the parameter space around the orbit of this putative planet, we ran a stability analysis using an N-body code. Furthermore, we explored the possibility of co-orbital bodies to the planet with a demodulation technique. We tested the hypothesis of ε Cyg being a hierarchical stellar triple by using a modified version of the N-body code. Alternative causes for the observed RV variations, such as stellar spots and oscillations, were examined by analyzing photometric data of the system and by comparing its properties to known variable stars with long secondary periods and heartbeat stars from the literature. Results. Our Keplerian model characterizes the orbit of the spectroscopic binary to higher precision than achieved previously, resulting in a semi-major axis of a = 15.8 AU, an eccentricity of e = 0.93, and a minimum mass of the secondary of msini = 0.265 M⊙. Additional short-period RV variations closely resemble the signal of a Jupiter-mass planet orbiting the evolved primary component with a period of 291 d, but the period and amplitude of the putative orbit change strongly over time. Furthermore, in our stability analysis of the system, no stable orbits could be found in a large region around the best fit. Both of these findings deem a planetary cause of the RV variations unlikely. Most of the investigated alternative scenarios also fail to explain the observed variability convincingly. Due to its very eccentric binary orbit, it seems possible, however, that ε Cyg could be an extreme example of a heartbeat system.es
dc.description.sponsorshipPart of this work was supported by the International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg, IMPRS-HD, Germany. We would like to thank the staff at the Lick Observatory for their support during the years of this project. We are also thankful to the CAT observers who assisted with this project, including Saskia Hekker, Simon Albrecht, David Bauer, Christoph Bergmann, Stanley Browne, Kelsey Clubb, Dennis Kugler, Christian Schwab, Julian Sturmer, Kirsten Vincke, and Dominika Wylezalek. This work also includes observations made with the Hertzsprung SONG telescope operated at the Spanish Observatorio del Teide on the island of Tenerife by the Aarhus and Copenhagen Universities and by the Instituto de Astrofisica de Canarias. Part of the work has been performed with the RV analysis tool Exo-Striker (Trifonov 2019), and many of the simulations have been carried out on the machine of the Novel Astronomical Instrumentation based on photonic light Reformatting (NAIR) group at the Landessternwarte Heidelberg. This research has been funded by the Spanish State Research Agency (AEI) Projects No.ESP2017-87676-C5-1-R and No. MDM-2017-0737 Unidad de Excelencia Maria de Maeztu-Centro de Astrobiologia (INTA-CSIC). Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant agreement no.: DNRF106). S.A. acknowledges the support from the Danish Council for Independent Research through the DFF Sapere Aude Starting Grant No. 4181-00487B. K.H.W. and M.H.L. are supported in part by Hong Kong RGC grant HKU 17305015. V.A. was supported by a research grant (00028173) from VILLUM FONDEN. The research made use of the SIMBAD database operated at CDS, Strasbourg, France, as well as of 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. We are grateful to Bogdan Ghiorghiu's contribution in the analysis of the RV measurements. We thank A. Leleu and A. Correia for private discussions on the co-orbital demodulation technique. We also thank H. Kjeldsen for his feedback concerning the jitter analysis, and R. Kuschnig for making the BRITE data available to us. Finally, we thank the anonymous referee for his very valuable review, especially his questions concerning the jitter analysis.es
dc.language.isoenges
dc.publisherEDP Scienceses
dc.relationinfo:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016/ESP2017-87676-C5-1-R-
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 Internationales
dc.rights.urihttps://creativecommons.org/licenses/by-nc-nd/4.0/-
dc.subjectPlanetary systemses
dc.subjectPlanets and satellites: detectiones
dc.subjectPlanets and satellites: dynamical evolution and stailityes
dc.subjectBinaries: closees
dc.subjectStars: horizontal branches
dc.subjectStars: oscillationses
dc.titlePrecise radial velocities of giant stars XV. Mysterious nearly periodic radial velocity variations in the eccentric binary ε Cygnies
dc.typeinfo:eu-repo/semantics/articlees
dc.contributor.orcidHeeren, P. [0000-0002-3662-9930]-
dc.contributor.orcidReffert, S. [0000-0002-0460-8289]-
dc.contributor.orcidTrifonov, T. [0000-0002-0236-775X]-
dc.contributor.orcidHoi Lee, M. [0000-0003-1930-5683]-
dc.contributor.orcidLillo Box, J. [0000-0003-3742-1987]-
dc.contributor.orcidAlbrecht, S. [0000-0003-1762-8235]-
dc.contributor.orcidFredslund Andersen, M. [0000-0002-9194-8520]-
dc.contributor.orcidPallé, P. L. [0000-0003-3803-4823]-
dc.identifier.doi10.1051/0004-6361/202040087-
dc.identifier.e-issn1432-0746-
dc.contributor.funderAgencia Estatal de Investigación (AEI)-
dc.contributor.funderDanish National Research Foundation-
dc.contributor.funderDanish Council for Independent Research-
dc.description.peerreviewedPeerreviewes
dc.identifier.funderhttp://dx.doi.org/10.13039/501100011033-
dc.type.hasVersioninfo:eu-repo/semantics/publishedVersion-
dc.rights.accessRightsinfo:eu-repo/semantics/openAccess-
dc.type.coarhttp://purl.org/coar/resource_type/c_6501-
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