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dc.contributor.authorSicilia-Aguilar, Aurora
dc.contributor.authorFang, Min
dc.contributor.authorRoccatagliata, Veronica
dc.contributor.authorCollier Cameron, Andrew
dc.contributor.authorKóspál, Ágnes
dc.contributor.authorHenning, Thomas
dc.contributor.authorÁbrahám, Peter
dc.contributor.authorSipos, Nikoletta
dc.identifier.citationSicilia-Aguilar , A , Fang , M , Roccatagliata , V , Collier Cameron , A , Kóspál , Á , Henning , T , Ábrahám , P & Sipos , N 2015 , ' The accretion dynamics of EX Lupi in quiescence : the star, the spot, and the accretion column ' , Astronomy & Astrophysics , vol. 580 , A82 .
dc.identifier.otherPURE: 192849882
dc.identifier.otherPURE UUID: 588a7d86-dee9-4f31-9d16-ab368d86d9d7
dc.identifier.otherBibCode: 2015arXiv150508011S
dc.identifier.otherBibCode: 2015A&A...580A..82S
dc.identifier.otherScopus: 84938807969
dc.identifier.otherORCID: /0000-0002-8863-7828/work/58531429
dc.identifier.otherWOS: 000360020200082
dc.description.abstractContext. EX Lupi is a young, accreting M0 star and the prototype of EXor variable stars. Its spectrum is very rich in emission lines, including many metallic lines with narrow and broad components. The presence of a close companion has also been proposed, based on radial velocity signatures. Aims: We use the metallic emission lines to study the accretion structures and to test the companion hypothesis. Methods: We analyse 54 spectra obtained during five years of quiescence time. We study the line profile variability and the radial velocity of the narrow and broad metallic emission lines. We use the velocity signatures of different species with various excitation conditions and their time dependency to track the dynamics associated with accretion. Results: We observe periodic velocity variations in the broad and the narrow line components, consistent with rotational modulation. The modulation is stronger for lines with higher excitation potentials (e.g. He II), which are likely produced in a confined area very close to the accretion shock. Conclusions: We propose that the narrow line components are produced in the post-shock region, while the broad components originate in the more extended, pre-shock material in the accretion column. All the emission lines suffer velocity modulation due to the rotation of the star. The broad components are responsible for the line-dependent veiling observed in EX Lupi. We demonstrate that a rotationally modulated line-dependent veiling can explain the radial velocity signature of the photospheric absorption lines, making the close-in companion hypothesis unnecessary. The accretion structure is locked to the star and very stable during the five years of observations. Not all stars with similar spectral types and accretion rates show the same metallic emission lines, which could be related to differences in temperature and density in their accretion structure(s). The contamination of photospheric signatures by accretion-related processes can be turned into a very useful tool for determining the innermost details of the accretion channels in the proximity of the star. The presence of emission lines from very stable accretion columns will nevertheless be a very strong limitation for the detection of companions by radial velocity in young stars, given the similarity of the accretion-related signatures with those produced by a companion. Appendices are available in electronic form at
dc.relation.ispartofAstronomy & Astrophysicsen
dc.rightsReproduced with permission from Astronomy & Astrophysics, © 2015 ESOen
dc.subjectStars: pre-main sequenceen
dc.subjectStars: variabilityen
dc.subjectStars: EX Lupien
dc.subjectProtoplanetary disksen
dc.subjectStars: variables: T Tauri, Herbig Ae/Been
dc.subjectStars: individual: EX Lupien
dc.subjectAccretion disksen
dc.subjectTechniques: spectroscopicen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleThe accretion dynamics of EX Lupi in quiescence : the star, the spot, and the accretion columnen
dc.typeJournal articleen
dc.contributor.institutionUniversity of St Andrews.School of Physics and Astronomyen
dc.description.statusPeer revieweden

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