J/A+A/697/A133ivo://CDS.VizieR/J/A+A/697/A133doi:10.26093/cds/vizier.36970133CDSAbdul Qadir Y.Berdyugin A.V.Piirola V.Sakanoi T.Kagitan M.,Berdyugina S.V.2025-08-04T20:01:03Z2025-05-15T09:10:36ZCDS support team

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

cds-question@unistra.frmultiple-starspolarimetryvisible-astronomyThis is a continuation of our study of early-type binaries with high-precision broad-band polarimetry. This time, we are presenting results of our observations of the massive O+O-type binary system HD 165052 located in the very young open cluster NGC 6530. Our aim was to investigate the variations of linear polarization in this system with time and obtain independent estimate of orbital period from polarization data. By fitting phase-locked variations of Stokes parameters q and u, it is possible to obtain independent estimates of orbit inclination i, orientation {Omega}, and the direction of rotation. We employed the Dipol-2 polarimeter in combination with the remotely controlled 60cm KVA and Tohoku T60 telescopes. Linear polarization measurements of HD 165052 were obtained in the B, V, and R passbands with an accuracy better than ~0.01%. Lomb-Scargle method of period search was applied to the acquired polarization data to identify present periodic signals. To study interstellar polarization in NGC 6530, we observed 25 cluster stars located in close proximity to the binary. Our observations clearly revealed periodic variations of Stokes parameters in all three passbands with the amplitude ~0.1%. Period search, applied to polarization data, detected unambiguous and strongest periodic signal at 1.47755+/-0.005d, that corresponds to half of the orbital period of 2.95510+/-0.005d. Our independent period search, performed on polarization data, supports a "shorter" value of the orbital period in HD 165052 determined from RV measurements done in the past and rejects "longer" value obtained very recently. In the observed polarization variations, the second terms of the Fourier harmonics are clearly dominating suggesting that light scattering material is symmetrically distributed with respect to the orbital plane. We concluded that the most probable polarization mechanism is the electron scattering in the interacting stellar winds. To evaluate the effect of non-periodic noise on the orbital parameters derived from analysis of periodic variations of polarization, we have employed rigorous Monte Carlo simulations for the available data. Thus, we derived our best estimate of the orbital inclination i as 55^+5^_-55_{deg}, and {Omega} as 148{deg} (328^+20^_-22_{deg} averaged over B, V, and R passbands. Our estimates provide direct and unambiguous evidence that non-periodic noise, if present, significantly reduce accuracy of orbital parameters obtained from high-precision polarization data for the low-inclination systems. Using the values of polarization variability amplitude, we estimated the mass-loss rate for the whole system to be (dM/dt=2.46x10^-7^+/-2.47x10^-8^M_{sun}/yr. The direction of the binary system rotation on the plane of the sky is clockwise. Our observations of HD 165052 neighbour stars revealed complex behaviour of interstellar polarization in the cluster NGC 6530.2025A&A...697A.133Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/697/A133CatalogResearchIsServedByTAP 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)J/A+A/670/A176 : B, V and R band polarimetry of AO Cas (Abdul Qadir+, 2023)J/A+A/677/A75 : B, V and R band polarimetry of DH Cep (Abdul Qadir+, 2023)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/697/A133https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/697/A133http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/697/A133https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/697/A133https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/697/A133http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/697/A133GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/697/A133/stokesubPolarimetric data of HD 165052, Stokes u in B passbandrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian datedtime.epochdoubleuStokes u parameter in Bandphys.polarization.stokesfloate_uStokes u parameter in Band errorstat.errorfloatBand[BVR] Bandinstr.bandpasscharJ/A+A/697/A133/stokesurPolarimetric data of HD 165052, Stokes u in R passbandrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian datedtime.epochdoubleuStokes u parameter in Bandphys.polarization.stokesfloate_uStokes u parameter in Band errorstat.errorfloatBand[BVR] Bandinstr.bandpasscharJ/A+A/697/A133/stokesuvPolarimetric data of HD 165052, Stokes u in V passbandrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian datedtime.epochdoubleuStokes u parameter in Bandphys.polarization.stokesfloate_uStokes u parameter in Band errorstat.errorfloatBand[BVR] Bandinstr.bandpasscharJ/A+A/697/A133/stokesqbPolarimetric data of HD 165052, Stokes q in B passbandrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian datedtime.epochdoubleqStokes q parameter in Bandphys.polarization.stokesfloate_qStokes q parameter in Band errorstat.errorfloatBand[BVR] Bandinstr.bandpasscharJ/A+A/697/A133/stokesqrPolarimetric data of HD 165052, Stokes q in R passbandrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian datedtime.epochdoubleqStokes q parameter in Bandphys.polarization.stokesfloate_qStokes q parameter in Band errorstat.errorfloatBand[BVR] Bandinstr.bandpasscharJ/A+A/697/A133/stokesqvPolarimetric data of HD 165052, Stokes q in v passbandrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian datedtime.epochdoubleqStokes q parameter in Bandphys.polarization.stokesfloate_qStokes q parameter in Band errorstat.errorfloatBand[BVR] Bandinstr.bandpasschar