J/AJ/123/3154ivo://CDS.VizieR/J/AJ/123/3154doi:10.26093/cds/vizier.51233154CDSDolphin A.E.Saha A.Claver J.Skillman E.D.Cole A.A.Gallagher J.S.,Tolstoy E.Dohm-Palmer R.C.Mateo M.2023-04-06T16:50:49Z2002-11-30T10:36:18ZCDS support team

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

cds-question@unistra.frvariable-starsvisible-astronomyWide-band photometryWe present the results of a search for short-period variable stars in Leo A. We have found 92 candidate variables, including eight candidate RR Lyrae stars. From the RR Lyrae stars, we measure a distance modulus of (m-M)0=24.51+/-0.12, or 0.80+/-0.04Mpc. This discovery of RR Lyrae stars confirms for the first time the presence of an ancient (older than ~11Gyr) population in Leo A, accounting for at least 0.1% of the galaxy's V luminosity. We have also discovered a halo of old (more than ~2Gyr) stars surrounding Leo A, with a scale length roughly 50% larger than that of the dominant young population. We also report the discovery of a large population of Cepheids in Leo A. The median absolute magnitude of our Cepheid sample is M_V_=-1.1, fainter than 96% of SMC and 99% of LMC Cepheids. Their periods are also unusual, with three Cepheids that are deduced to be pulsating in the fundamental mode having periods of under 1 day. Upon examination, these characteristics of the Leo A Cepheid population appear to be a natural extension of the classical Cepheid period-luminosity relations to low metallicity, rather than being indicative of a large population of "anomalous" Cepheids. We demonstrate that the periods and luminosities are consistent with the expected values of low-metallicity blue helium-burning stars (BHeB's), which populate the instability strip at lower luminosities than do higher metallicity BHeB's. Observations of Leo A were obtained at the WIYN 3.5 m telescope on the nights of 20-22 December 2000, using the MIMO camera.2002AJ....123.3154Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/123/3154CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/123/3154https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/123/3154http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/123/3154https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/123/3154https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/123/3154http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/123/3154GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/123/3154/table2BV light curvesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint[DSC2002]Variable name (VN-CNN)meta.id;meta.maincharBand[RV] Bandinstr.bandpasscharHJDHeliocentric Julian date of observationdtime.epochdoublemagB or V magnitudemagphot.mag;em.opt.Vfloate_magrms uncertainty on magmagstat.errorfloatJ/AJ/123/3154/table3Variable starsQ[1/4] Quality flag (3)meta.code.qualintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint[DSC2002]Variable name (1)meta.id;meta.maincharprimaryLCurvePlot the light curvemeta.refcharChipChip numbermeta.id;instrintXposX position (2)pixpos.cartesian.x;instr.detfloatYposY position (2)pixpos.cartesian.y;instr.detfloatVmagV magnitudemagphot.mag;em.opt.Vfloate_Vmagrms uncertainty on Vmagmagstat.errorfloatRmagR magnitudemagphot.mag;em.opt.Rfloate_Rmagrms uncertainty on Rmagmagstat.errorfloatPerPerioddtime.periodfloate_Perrms uncertainty on Perdstat.errorfloatn_Per[*] *: Upper limits of the periods of stars C2-V08, C2-V63, and C2-V64 are unconstrainedmeta.notecharClassVariable classification (4)meta.code;src.varchar