J/A+A/670/A176ivo://CDS.VizieR/J/A+A/670/A176doi:10.26093/cds/vizier.36700176CDSAbdul Qadir Y.Berdyugin A.V.Piirola V.Sakanoi T.Kagitan M.2024-11-28T20:02:02Z2023-02-23T08:04:43ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.freclipsing-binary-starspolarimetryvisible-astronomyThe fact that the O-type close binary star system AO~Cassiopeiae exhibits variable phase-locked linear polarization has been known since the mid-1970s. In this work, we re-observe the polarization arising from this system more than 50 years later to better estimate the interstellar polarization and to independently derive the orbital parameters, such as inclination, i, orientation, {Omega}, and the direction of the rotation for the inner orbit from the phase-folded polarization curves of the Stokes q and u parameters. The Dipol-2 polarimeter was used to obtain linear polarization measurements of AO Cassiopeiae in the B, V, and R passbands with the T60 remotely controlled telescope at an unprecedented accuracy level of ~0.003%. We have obtained the first proper quantification of the interstellar polarization in the direction heading towards AO Cas by observing the polarization of three neighboring field stars. We employed a Lomb-Scargle algorithm and detected a clear periodic signal for the orbital period of AO Cas. The standard analytical method based on a two-harmonics Fourier fit was used to obtain the inclination and orientation of the binary orbit. Our polarimetric data exhibited an unambiguous periodic signal at 1.76-days, thus confirming the orbital period of the binary system of 3.52-days. Most of the observed polarization is of interstellar origin. The de-biased values of the orbital inclination are i=63^+2^_-3_{deg} and orientation of {Omega}=29{deg} (209{deg}) +/-8{deg}. The direction of the binary system rotation on the plane of the sky is clockwise.2023A&A...670A.176Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/670/A176CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/591/A92 : BVR polarimetry of HD 48099 (Berdyugin+, 2016)J/A+A/611/A69 : B,V and R band polarimetry of lambda Tau (Berdyugin+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/670/A176https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/670/A176http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/670/A176https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/670/A176https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/670/A176http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/670/A176GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/670/A176/polPolarization data of AO CasrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDJulian datedtime.epochdoubleq(B)Stokes q in B-bandphys.polarization.stokesfloatu(B)Stokes u in B-bandphys.polarization.stokesfloate_q(B)Error of q(B) and u(B)stat.errorfloatq(V)Stokes q in V-bandphys.polarization.stokesfloatu(V)Stokes u in V-bandphys.polarization.stokesfloate_q(V)Error of q(V) and u(V)stat.errorfloatq(R)Stokes q in R-bandphys.polarization.stokesfloatu(R)Stokes u in R-bandphys.polarization.stokesfloate_q(R)Error of q(R) and u(R)stat.errorfloat