J/MNRAS/535/1586ivo://CDS.VizieR/J/MNRAS/535/1586doi:10.26093/cds/vizier.75351586CDSCotton D.V.Bailey J.Kedziora-Chudczer L.Bott K.De Horta A.,Filcek N.Marshall J.P.Melville G.Buzasi D.L.Boiko I.Borsato N.W.,Perkins J.Opitz D.Melrose S.Gruening G.Evensberget D.Zhao J.2025-02-27T20:16:13Z2025-01-21T11:39:49ZCDS support team

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

cds-question@unistra.frstandard-starspolarimetryObservations of polarization position angle ({theta}) standards made from 2014 to 2023 with the High Precision Polarimetric Instrument (HIPPI) and other HIPPI-class polarimeters in both hemispheres are used to investigate their variability. Multi-band data were first used to thoroughly recalibrate the instrument performance by bench-marking against carefully selected literature data. A novel Co-ordinate Difference Matrix (CDM) approach - which combines pairs of points - was then used to amalgamate monochromatic (g' band) observations from many observing runs and re-determine {theta} for 17 standard stars. The CDM algorithm was then integrated into a fitting routine and used to establish the impact of stellar variability on the measured position angle scatter. The approach yields variability detections for stars on long time scales that appear stable over short runs. The best position angle standards are l Car, o Sco, HD 154445, HD 161056 and {iota}^1^ Sco which are stable to <=0.123deg. Position angle variability of 0.27-0.82 deg, significant at the 3-{sigma} level, is found for 5 standards, including the Luminous Blue Variable HD 160529 and all but one of the other B/A-type supergiants (HD 80558, HD 111613, HD 183143 and 55 Cyg), most of which also appear likely to be variable in polarization magnitude (p) - there is no preferred orientation for the polarization in these objects, which are all classified as {alpha} Cygni variables. Despite this we make six key recommendations for observers - relating to data acquisition, processing and reporting - that will allow them to use these standards to achieve <0.1deg precision in the telescope position angle with similar instrumentation, and allow data sets to be combined more accurately.2024MNRAS.535.1586Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/535/1586CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/535/1586https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/535/1586http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/535/1586https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/535/1586https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/535/1586http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/535/1586GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/535/1586/stars (List of studied stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/535/1586/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/535/1586/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/535/1586/stars?GETtext/xml+votable180.050000true20.020458358.23161110.0055555555555555566/461 2940 15392 19009 24340 28804 29621 30128 30718 30818 31133 37303 37754 42334 42988 43033 45105https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/535/1586?format=asciidefaultJ/MNRAS/535/1586/starsList of studied starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObjectHD catalogue numbermeta.id;meta.maincharRAJ2000Simbad right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Simbad Declination (J2000)pos.eq.dec;meta.mainNobsNumber of observations on obs.dat tablemeta.numberintSimbadSimbad column added by the CDSmeta.ref.urlcharJ/MNRAS/535/1586/runsSummary of observing runsfTelTelescope f-numberphys.size;instr.telfloatBLBarlow lens used: x2 or NA (3)meta.codecharTPAeAdopted error in telescope position angledegstat.errorfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRunRun designation: [X]YYYYMMM[S] (1)meta.id;obscharUTStartUT Start date of observation: YYYY-MM-DDtime.start;obsnullableUTEndUT End date of observation: YYYY-MM-DDtime.end;obsnullableInstInstrment name: HIPPI, HIPPI-2 or Mini-HIPPImeta.id;instrcharMod-ErModulator and performance era: MMM-EN (2)meta.codecharTelTelescope: AAT, PIN, GN, OOS, UNSW or WSUinstr.telcharJ/MNRAS/535/1586/obsHigh polarization standard observationspobsPolarization magnitude of observation(10-6)phys.polarizationfloate_pobsError in pobs from measurement statistics(10-6)stat.errorfloatPAobsPosition angle of observation, 2020 Equinoxdegpos.posAng;obsfloate_PAobsPosition angle error from measurement statisticsdegstat.errorfloatppredPredicted polarization magnitude(10-6)phys.polarizationfloatPApredPredicted position angledegpos.posAngfloatNotes[S/M] Notes (4)meta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObs.dateObservation mid-point: YYYY-MM-DDThh:mm:ssstime.epochnullableDwellObservation dwell timestime.intervalintRunRun designation: [X]YYYYMMM[S] (1)meta.id;obscharObjectHD catalogue numbermeta.id;meta.maincharApDiamAperture diameterarcsecphys.angSize;instr.fovfloatSkySky timing at each PA (2)meta.codecharFilterFilter (3)meta.id;instr.filtercharPMT[B/R] Blue (B) or Red (R) sensitive PMTmeta.codecharWLeffEffective wavelengthnmem.wl.effectivefloatEff1/efficiency correction appliedinstr.paramdoubleExpTimeExposure timestime.duration;obs.exposureint