J/AJ/149/194ivo://CDS.VizieR/J/AJ/149/194doi:10.26093/cds/vizier.51490194CDSLee J.W.Youn J.-H.Park J.-H.Wolf M.2017-06-20T13:17:01Z2015-06-12T09:44:30ZCDS support team

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

cds-question@unistra.freclipsing-binary-starsinfrared-photometryvisible-astronomybroad-band-photometryccd-photometryNew CCD photometry is presented for the hot overcontact binary DK Cyg together with reasonable explanations for the light and period variations. Historical light and velocity curves from 1962 to 2012 were simultaneously analyzed with the Wilson-Devinney (W-D) synthesis code. The brightness disturbances were satisfactorily modeled by applying a magnetic cool spot on the primary star. Based on 261 times of minimum light that include 116 new timings and span more than 87 years, a period study reveals that the orbital period has varied due to a periodic oscillation superimposed on an upward parabola. The period and semi-amplitude of the modulation are about 78.1years and 0.0037days, respectively. This detail is interpreted as a light-travel-time effect due to a circumbinary companion with a minimum mass of M_3_=0.065M_{sun}_, within the theoretical limit of ~0.07M_{sun}_ for a brown dwarf star. The observed period increase at a fractional rate of +2.74x10^-10^ is in excellent agreement with that calculated from our W-D synthesis. Mass transfer from the secondary to the primary component is mainly responsible for the secular period change. We examined the evolutionary status of the DK Cyg system from the absolute dimensions.2015AJ....149..194Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/149/194CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)J/AJ/145/100 : Differential BVR light curves of EP And (Lee+, 2013)J/A+A/289/137 : DK Cygni light curve (Awadalla, 1994)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/149/194https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/149/194http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/149/194https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/149/194https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/149/194http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/149/194GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfraredOpticaldefaultJ/AJ/149/194/table6Observed photoelectric and CCD times of minimum light for DK CygrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric Julian Date (HJD-2400000)dtime.epochdoublee_HJD? Error in HJDdstat.error;time.epochdoublenullableHJEDHeliocentric Julian Ephemeris Date in the Terrestrial Time (TT) scale (HJED-2400000)dtime.epoch;pos.heliocentricdoubleE[-4753/39989] Epoch (cycle) (is integer for primary minimum, and half-nitegter for secondary minimum)time.epochfloatO-C[-0.005/0.004] The (O-C) residualdstat.fit.residual;stat.fit.omcdoubleMinMinimum type (I or II)meta.notenullableRefReference; in refs.dat filemeta.ref;pos.framecharJ/AJ/149/194/refsReferencesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRefReference identifierpos.frame;meta.maincharprimaryBibCodeBibliographic codemeta.bib.bibcodecharAutAuthor's namemeta.bib.authorcharComCommentsmeta.notecharJ/AJ/149/194/table1CCD photometric observations of DK Cyg observed at Sobaeksan Optical Astronomy Observatory (SOAO)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD-BHeliocentric Julian Date of B band observationdtime.epochdoubleDBmagDifferential B band magnitude (1)magphot.mag;em.opt.B;arith.difffloatHJD-V? Heliocentric Julian Date of V band observationdtime.epochdoublenullableDVmag? Differential V band magnitude (1)magphot.mag;em.opt.V;arith.difffloatnullableHJD-R? Heliocentric Julian Date of R band observationdtime.epochdoublenullableDRmag? Differential R band magnitude (1)magphot.mag;em.opt.R;arith.difffloatnullable