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Asymmetric shocks in $\chi$ Cyg observed with linear spectropolarimetry

hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorARISTE, A. López
hal.structure.identifierInstitut de Planétologie et d'Astrophysique de Grenoble [IPAG]
dc.contributor.authorTESSORE, B.
hal.structure.identifierInstituto de Astrofisica de Canarias [IAC]
hal.structure.identifierUniversidad de La Laguna [Tenerife - SP] [ULL]
hal.structure.identifierIstituto Ricerche Solari Locarno
dc.contributor.authorCARLÍN, E. S.
hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorMATHIAS, Ph.
hal.structure.identifierLaboratoire Univers et Particules de Montpellier [LUPM]
dc.contributor.authorLÈBRE, A.
hal.structure.identifierLaboratoire Univers et Particules de Montpellier [LUPM]
dc.contributor.authorMORIN, J.
hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorPETIT, P.
hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorAURIERE, M.
hal.structure.identifierObservatoire de Haute-Provence [OHP]
dc.contributor.authorGILLET, D.
hal.structure.identifierLaboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
dc.contributor.authorHERPIN, Fabrice
dc.date.accessioned2021-07-07T15:47:57Z
dc.date.available2021-07-07T15:47:57Z
dc.date.issued2019-12
dc.identifier.issn0004-6361
dc.identifier.urihttps://oskar-bordeaux.fr/handle/20.500.12278/95348
dc.description.abstractEnAims: From a coherent interpretation of the linear polarisation detected in the spectral lines of the Mira star $\chi$ Cyg, we derive information about the dynamics of the stellar photosphere, including pulsation. Methods: From spectropolarimetric observations of $\chi$ Cyg, we perform careful analysis of the polarisation signals observed in atomic and molecular lines, both in absorption and emission, using the radiative transfer in the polarisation context, through two mechanisms: intrinsic polarisation and continuum depolarisation. We also explain the observed line doubling phenomenon in terms of an expanding shell in spherical geometry, which allows us to pinpoint the coordinates over the stellar disk with enhanced polarisation. Results: We find that the polarised spectrum of $\chi$ Cyg is dominated by intrinsic polarisation, with a negligible continuum depolarisation. The observed polarised signals can only be explained by assuming that this polarisation is locally enhanced by velocity fields. During the pulsation, radial velocities are not homogeneous over the disk. We map these regions of enhanced velocities. Conclusions: We have set an algorithm to distinguish in any stellar spectra of linear polarisation the origin of this polarisation and the way to increase signal by coherently adding many lines with an appropriated weight. Applied to the Mira star $\chi$ Cyg, we reached the unexpected result that during the pulsation, velocities are radial but not homogeneous over the disk. The reason for these local velocity enhancements are probably related to the interplay between the atmospheric pulsation dynamics and the underlying stellar convection.
dc.language.isoen
dc.publisherEDP Sciences
dc.subject.enTechniques: polarimetry
dc.subject.enStars: variable
dc.subject.enStars: imaging
dc.subject.enStars: HD 187796
dc.title.enAsymmetric shocks in $\chi$ Cyg observed with linear spectropolarimetry
dc.typeArticle de revue
dc.identifier.doi10.1051/0004-6361/201936189
dc.subject.halPlanète et Univers [physics]/Astrophysique [astro-ph]/Astrophysique stellaire et solaire [astro-ph.SR]
dc.identifier.arxiv1909.03720
bordeaux.journalAstronomy and Astrophysics - A&A
bordeaux.pageA30
bordeaux.volume632
bordeaux.hal.laboratoriesLaboratoire d'Astrophysique de Bordeaux (LAB) - UMR 5804*
bordeaux.institutionCNRS
bordeaux.institutionUniversité de Bordeaux
bordeaux.peerReviewedoui
hal.identifierhal-02282387
hal.version1
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-02282387v1
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