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Asymmetric shocks in χ Cygni observed with linear spectropolarimetry

hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorLÓPEZ ARISTE, A.
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.
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.authorAURIÈRE, M.
hal.structure.identifierObservatoire de Haute-Provence [OHP]
dc.contributor.authorGILLET, D.
hal.structure.identifierLaboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
hal.structure.identifierFEMIS 2021
dc.contributor.authorHERPIN, F.
dc.date.issued2019-12
dc.identifier.issn0004-6361
dc.description.abstractEnAims. We derive information about the dynamics of the stellar photosphere, including pulsation, from a coherent interpretation of the linear polarisation detected in the spectral lines of the Mira star χ Cyg. Methods. From spectropolarimetric observations of χ Cyg, we performed a careful analysis of the polarisation signals observed in atomic and molecular lines, both in absorption and emission, using radiative transfer in the context of polarisation produced 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 disc with enhanced polarisation. Results. We find that the polarised spectrum of χ Cyg is dominated by intrinsic polarisation and has 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 disc. We map these regions of enhanced velocities. Conclusions. We set an algorithm to distinguish the origin of this polarisation in any stellar spectra of linear polarisation and to find a way to increase the signal by coherently adding many lines with an appropriated weight. Applied to the Mira star χ Cyg, we reached the unexpected result that during the pulsation, velocities are radial but not homogeneous over the disc. 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.enStars: HD 187796
dc.subject.enstars
dc.subject.envariables
dc.subject.engeneral -stars
dc.subject.enimaging -techniques
dc.subject.enpolarimetric
dc.subject.enTechniques: polarimetry
dc.title.enAsymmetric shocks in χ Cygni observed with linear spectropolarimetry
dc.typeArticle de revue
dc.identifier.doi10.1051/0004-6361/201936189
dc.subject.halPhysique [physics]/Astrophysique [astro-ph]
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.peerReviewedoui
hal.identifierhal-03190436
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-03190436v1
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