J/AJ/154/217ivo://CDS.VizieR/J/AJ/154/217doi:10.26093/cds/vizier.51540217CDSSirorattanakul K.Engle S.Pepper J.Wells M.Laney C.D.,Rodriguez J.E.Stassun K.G.2018-10-01T05:45:09Z2018-08-14T08:01:10ZCDS support team

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

cds-question@unistra.frvariable-starsvisible-astronomybroad-band-photometryThe Cepheid Period-Luminosity law is a key rung on the extragalactic distance ladder. However, numerous Cepheids are known to undergo period variations. Monitoring, refining, and understanding these period variations allows us to better determine the parameters of the Cepheids themselves and of the instability strip in which they reside, and to test models of stellar evolution. VZ Cyg, a classical Cepheid pulsating at ~4.864 days, has been observed for over 100 years. Combining data from literature observations, the Kilodegree Extremely Little Telescope (KELT) transit survey, and new targeted observations with the Robotically Controlled Telescope (RCT) at Kitt Peak, we find a period change rate of dP/dt=-0.0642+/-0.0018 s/yr. However, when only the recent observations are examined, we find a much higher period change rate of dP/dt=-0.0923+/-0.0110 s/yr. This higher rate could be due to an apparent long-term (P~26.5 years) cyclic period variation. The possible interpretations of this single Cepheid's complex period variations underscore both the need to regularly monitor pulsating variables and the important benefits that photometric surveys such as KELT can have on the field. Further monitoring of this interesting example of Cepheid variability is recommended to confirm and better understand the possible cyclic period variations. Further, Cepheid timing analyses are necessary to fully understand their current behaviors and parameters, as well as their evolutionary histories.2017AJ....154..217Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/154/217CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/404/423 : BVI photometry of Galactic Cepheids (Tammann+, 2003)J/PAZh/39/942 : Galactic classical Cepheids properties (Marsakov+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/154/217https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/154/217http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/154/217https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/154/217https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/154/217http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/154/217GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/154/217/table4O-C Data for VZ CygrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTmaxTime of maximum light (HJD)dtime.epochdoubleEpoch[-4333/3281] Epoch of the observationdtime.epochintO-C[-0.4421/0.0418] O-C for Epochdtime;arith.difffloatWeight[1/3] Weightstat.weight;phys.atmol.weightinte_O-C[0.0025/0.1458]? Uncertainty in O-Cdstat.error;stat.fit.omcfloatnullableRefReferencemeta.ref;pos.framecharBibcodeBibcode of the reference or commentmeta.bib.bibcodecharJ/AJ/154/217/table2KELT Photometry of VZ CygrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric Julian Datedtime.epochdoubleKELTmag[-0.493/1.335] Relative KELT instrument magnitudemagphot.magfloate_KELTmag[0.001/0.016] Formal error in KELTmagmagstat.error;phot.magfloatJ/AJ/154/217/table3RCT BV Photometry of VZ Cyge_mag[0.0003/0.0414] Formal error in magmagstat.error;phot.magfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFilt[BV] Filter usedinstr.setup;instr.filtercharHJDHeliocentric Julian Datedtime.epochdoublemag[8.6067/10.2972] Apparent RCT magnitude in Filtmagphot.magfloat