J/MNRAS/413/1275ivo://CDS.VizieR/J/MNRAS/413/1275doi:10.26093/cds/vizier.74131275CDSBramich D.M.Figuera Jaimes R.Giridhar S.Arellano Ferro A.2024-07-13T20:15:11Z2012-04-02T12:51:51ZCDS support team

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

cds-question@unistra.frglobular-star-clustersvariable-starsccd-photometryWe present the results from 10 nights of observations of the globular cluster NGC 6981 (M72) in the V, R and I Johnson wavebands. We employed the technique of difference image analysis to perform precision differential photometry on the time-series images, which enabled us to carry out a census of the understudied variable star population of the cluster. We show that 20 suspected variables in the literature are actually non-variable, and we confirm the variable nature of another 29 variables while refining their ephemerides. We also detect 11 new RR Lyrae variables and three new SX Phe variables, bringing the total confirmed variable star count in NGC 6981 to 43. We performed Fourier decomposition of the light curves for a subset of RR Lyrae stars and used the Fourier parameters to estimate the fundamental physical parameters of the stars using relations available in the literature. Mean values of these physical parameters have allowed us to estimate the physical parameters of the parent cluster. We derive a metallicity of [Fe/H]_ZW_~-1.48+/-0.03 on the Zinn & West scale (or [Fe/H]_UVES_~-1.38+/-0.03 on the new Carretta et al. scale) for NGC 6981, and distances of ~16.73+/-0.36 and ~16.68+/-0.36kpc from analysis of the RR0 and RR1 stars separately. We also confirm the Oosterhoff type I classification for the cluster, and show that our colour-magnitude data are consistent with the age of ~12.75+/-0.75Gyr derived by Dotter et al.2011MNRAS.413.1275Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/413/1275CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/413/1275https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/413/1275http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/413/1275https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/413/1275https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/413/1275http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/413/1275GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/413/1275/table23 (Celestial coordinates for all the confirmed variables in our field of view, except V27 and V35 which lie outside of our field of view and details of all confirmed variables in NGC 6981)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/413/1275/table23?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/413/1275/table23?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/413/1275/table23?GETtext/xml+votable180.050000true313.3796667-12.55330560.0055555555555555566/48952https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/413/1275?format=asciiOpticaldefaultJ/MNRAS/413/1275/table23Celestial coordinates for all the confirmed variables in our field of view, except V27 and V35 which lie outside of our field of view and details of all confirmed variables in NGC 6981LCShow the light curvesmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintVNameVariable Star ID (VN or VNN, NN<=56)meta.id;meta.maincharRAJ2000? Right ascension (J2000.0) (1)pos.eq.ra;meta.mainnullableDEJ2000? Declination (J2000.0) (1)pos.eq.dec;meta.mainnullableK95Kadla et al. (1995A&A...302..723K) candidate variables ID, <Cl* NGC 6981 KBP AN> in Simbadmeta.idcharVTypeVariable Type (RR0, RR0/RR1, RR1 or SX Phe)meta.code;src.varcharu_VType[abc] Uncertain variable type (2)meta.notecharBlendBlend Guide: Inner or Outer (3)obs.fieldcharNmax? Number of observed maxima (4)meta.numberintnullableNmin? Number of observed minima (4)meta.numberintnullableTmax? HJD epoch of maximum lightdtime.epochdoublenullablen_Tmax[d] Uncertainty flag on Tmax (5)meta.notecharPer? Perioddtime.perioddoublenullablen_Per[efg] Note on Per (6)meta.notecharPerS? Period from Shapley & Ritchie, 1920ApJ....52..232S (7)dtime.perioddoublenullablen_PerS[h] PerS does not match our data (8)meta.notecharPerR? Period from Rosino (1953, Pub. Oss. Bologna, 6, 49 (No.2)) (7)dtime.perioddoublenullablen_PerR[h] PerR does not match our data (8)meta.notecharPerN? Period from Nobili (1957MmSAI..28..141N) (7)dtime.perioddoublenullablen_PerN[h] PerN does not match our data (8)meta.notecharPerD? Period from Dickens & Flinn (1972MNRAS.158...99D) (7)dtime.perioddoublenullablen_PerD[h] PerD does not match our data (8)meta.notecharSimbadSimbad column added by the CDSmeta.refcharJ/MNRAS/413/1275/table4CCD time-series V, R, and I photometry of 41 variables in NGC6981pPhotometric scale factorarith.factorfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintVNameVariable star ID, as in table4meta.id;meta.maincharHJDHeliocentric Julian date at mid-exposuredtime.epochdoublemagst? Standard magnitudemagphot.magfloatnullablemaginstInstrumental magnitudemagphot.magfloate_magMagnitude uncertainty (standard or instrumental)magstat.error;phot.magfloatFrefReference flux (in ADU/s unit)s**-1meta.ref;phot.fluxdoublee_FrefReference flux uncertainty (in ADU/s unit)s**-1stat.errorfloatDFluxDifference flux (in ADU/s unit)s**-1meta.unit;phot.flux;arith.diffdoublee_DFluxDifference flux uncertainty (in ADU/s unit)s**-1stat.errorfloatFilter[VRI] Observation filterobs.param;obschar