J/ApJ/463/26ivo://CDS.VizieR/J/ApJ/463/26doi:10.26093/cds/vizier.14630026CDSKelson D.D.Illingworth G.D.Freedman W.F.Graham J.A.Hill R.,Madore B.F.Saha A.Stetson P.B.Kennicutt Jr.R.C.Mould J.R.,Hughes S.M.Ferrarese L.Phelps R.Turner A.Cook K.H.Ford H.,Hoessel J.G.Huchra J.2017-06-19T07:57:36Z2008-06-29T09:39:41ZCDS support team

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

cds-question@unistra.frvariable-starsphotometryWe report on the discovery of 29 Cepheid variables in the galaxy M101 using the original Wide Field Camera (WFC) and the new Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope. We observed a field in M101 at 17 independent epochs in V (F555W), five epochs in I (F785LP/F814W), and one epoch in B (F439W), with a time interval baseline of 381 days. We have found Cepheids with periods ranging from 10 to 60 days. The data have been calibrated using WFPC2 observations with zero points derived from Omega Cen, Pal 4, and NGC 2419 observations. This calibration has been verified by using the Medium Deep Survey (MDS) WFC photometric zero points, and ground-based secondary standards in V and I. The V calibrations agree to +/-0.06mag, and the I calibrations agree to +/-0.4mag. We have constructed V and I period-luminosity (PL) relations and have derived apparent distance moduli based on a distance modulus for the Large Magellanic Cloud (LMC) of 18.50mag and a reddening of E(B-V)=0.10mag to the LMC Cepheids. Period-residual minimization was used to minimize the effects of Malmquist bias on the period-luminosity relation fitting process. Using a Galactic extinction law and the apparent V and I distance moduli, we have found a mean reddening for the M101 sample of E(B-V)=0.03mag and a true distance modulus to M101 of 29.34+/-0.17mag, corresponding to a distance of 7.4+/-0.6Mpc. The sources of error have been rigorously tracked through an error budget; systematic and random errors contribute roughly equally to the quoted error. The mean gas-phase metal abundances in the LMC and in the M101 outer field are similar so we expect metallicity effects to be minimal. These Cepheids will be used in conjunction with results from a Key Project search for Cepheids in an inner field, where the metallicity is larger by a factor of 5, to probe the effects of abundance on the Cepheid period-luminosity relation.1996ApJ...463...26Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/463/26CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/507/655 : VI photometry of new Cepheids in NGC 2541 (Ferrarese+, 1998)J/ApJ/508/491 : M101 Cepheids (Stetson+, 1998)J/ApJ/523/540 : VI photometry of new Cepheids in NGC 3319 (Sakai+, 1999)J/ApJ/521/155 : New Cepheids and distance to NGC 4535 (Macri+, 1999)J/ApJ/523/540 : VI photometry of new Cepheids in NGC 3319 (Sakai+, 1999)J/ApJ/529/723 : VI photometry of Cepheids (Gibson+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/463/26https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/463/26http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/463/26https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/463/26https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/463/26http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/463/26GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapHSTOpticaldefaultJ/ApJ/463/26/tableb1V photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCepCepheid numbermeta.id;meta.mainintPerPerioddtime.periodfloatJDJulian date, midpoint of individual exposuredtime.epochdoubleCCDWhich CCD the star can be found inmeta.id;instrintXposX position on CCD framepixpos.cartesian.x;instr.detfloatYposY position on CCD framepixpos.cartesian.y;instr.detfloatVmagCalibrated F555W magnitudemagphot.mag;em.opt.Vfloate_VmagALLFRAME uncertainty in F555W magnitudemagstat.error;phot.mag;em.opt.VfloatJ/ApJ/463/26/tableb2I photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCepCepheid numbermeta.id;meta.mainintPerPerioddtime.periodfloatJDJulian date, midpoint of individual exposuredtime.epochdoubleCCDWhich CCD the star can be found inmeta.id;instrintXposX position on CCD framepixpos.cartesian.x;instr.detfloatYposY position on CCD framepixpos.cartesian.y;instr.detfloatImagCalibrated F814W magnitudemagphot.mag;em.opt.Ifloate_ImagALLFRAME uncertainty in F814W magnitudemagstat.error;phot.mag;em.opt.IfloatJ/ApJ/463/26/table2Cepheids observed (mean coordinates)PerPeriod, in days.dtime.periodfloatCCDChip numbermeta.id;instrintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCepCepheid numbermeta.id;meta.mainintprimaryXposPosition of Cepheid along X axispixphys.angSizefloatYposPosition of Cepheid along Y axispixphys.angSizefloatPlotSimbad column added by the CDSmeta.ref.urlchar