J/ApJ/767/62ivo://CDS.VizieR/J/ApJ/767/62doi:10.26093/cds/vizier.17670062CDSGarofalo A.Cusano F.Clementini G.Ripepi V.Dall'Ora M.,Moretti M.I.Coppola G.Musella I.Marconi M.2014-12-30T16:31:50Z2014-12-16T16:48:47ZCDS support team

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

cds-question@unistra.frvariable-starsvisible-astronomyWide-band photometrygalaxiesmetallicityWe have performed the first study of the variable star population of Ursa Major I (UMa I), an ultra-faint dwarf satellite recently discovered around the Milky Way (MW) by the Sloan Digital Sky Survey. Combining time series observations in the B and V bands from four different telescopes, we have identified seven RR Lyrae stars in UMa I, of which five are fundamental-mode (RRab) and two are first-overtone pulsators (RRc). Our V, B-V color-magnitude diagram of UMa I reaches V~23mag (at a signal-to-noise ratio of ~6) and shows features typical of a single old stellar population. The mean pulsation period of the RRab stars <P_ab_>=0.628, {sigma}=0.071 days (or <P_ab_>=0.599, {sigma}=0.032 days, if V4, the longest period and brightest variable, is discarded) and the position on the period-amplitude diagram suggest an Oosterhoff-intermediate classification for the galaxy. The RR Lyrae stars trace the galaxy horizontal branch (HB) at an average apparent magnitude of <V(RR)>=20.43+/-0.02mag (average on six stars and discarding V4), giving in turn a distance modulus for UMa I of (m-M)_0_=19.94+/-0.13mag, distance d=97.3_-5.7_^+6.0^kpc, in the scale where the distance modulus of the Large Magellanic Cloud is 18.5+/-0.1mag. Isodensity contours of UMa I red giants and HB stars (including the RR Lyrae stars identified in this study) show that the galaxy has an S-shaped structure, which is likely caused by the tidal interaction with the MW. Photometric metallicities were derived for six of the UMa I RR Lyrae stars from the parameters of the Fourier decomposition of the V-band light curves, leading to an average metal abundance of [Fe/H]=-2.29dex ({sigma}=0.06dex, average on six stars) on the Carretta et al. (2009, J/A+A/505/117) metallicity scale.2013ApJ...767...62Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/767/62CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)J/ApJ/756/121 : Variable stars in Her dwarf galaxy (Musella+, 2012)J/ApJ/756/108 : HST VI phot. of variable stars in Leo T (Clementini+, 2012)J/ApJ/752/42 : BV time series in Ursa Major II (Dall'Ora+, 2012)J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)J/ApJ/678/865 : LONEOS-I RR Lyrae stars (Miceli+, 2008)J/ApJ/674/L81 : Variable stars in dwarf galaxy CVn I (Kuehn+, 2008)J/A+A/421/937 : Metal abundances of LMC RR Lyrae (Gratton+, 2004)J/A+A/312/111 : [Fe/H] from RR Lyrae light curves (Jurcsik+, 1996)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/767/62https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/767/62http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/767/62https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/767/62https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/767/62http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/767/62GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/767/62/table2 (Identification and properties of the RR Lyrae stars identified in UMa I)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/767/62/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/767/62/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/767/62/table2?GETtext/xml+votable180.050000true158.74666751.9520280.0055555555555555566/6021 6023 60323.322582951404819e-19 4.920466254354166e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/767/62?format=asciiOpticaldefaultJ/ApJ/767/62/table3Johnson-Cousins B, V photometry of UMa I variable starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDStar identifier (V1 to V7)meta.id;meta.maincharTypeRR Lyrae type (RRab or RRc)meta.notecharFiltFilter used in the observation (B or V)instr.setup;obscharHJDHeliocentric Julian Date of the observation; HJD-2450000dtime.epochdoublemag[19.6/21.5] Observed magnitude in Filtmagphot.magfloate_mag[0.01/0.4] Uncertainty in magmagstat.error;phot.magfloatJ/ApJ/767/62/table2Identification and properties of the RR Lyrae stars identified in UMa ILCLight curvesmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDStar identifier (V1 to V7)meta.id;meta.maincharNpNumber of photometric measures for this star (table 3)meta.numberintnullableRAJ2000Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.mainTypeRR Lyrae type (RRab or RRc)meta.notecharPer[0.3/0.8] Pulsation period (1)dtime.perioddoubleHJDHeliocentric Julian Day of maximum light; HJD-2454000dtime.epoch;stat.maxfloat<Bmag>[20.5/21] Intensity-weighted mean B magnitudemagphot.mag;em.opt.Bfloat<Vmag>[20/20.5] Intensity-weighted mean V magnitudemagphot.mag;em.opt.VfloatBamp[0.3/1.4] B-band amplitudemagphot.mag;em.opt.BfloatVamp[0.3/1.1] V-band amplitudemagphot.mag;em.opt.Vfloat[Fe/H][-2.3/-2.1]? Spectroscopic metallicity (2)log(Sun)phys.abund.Zfloatnullable[Fe/H]p[-2.4/-2.2]? Photometric metallicity (3)log(Sun)phys.abund.Zfloatnullablee_[Fe/H]p[0.1/0.3]? [Fe/H]p uncertainty (3)log(Sun)stat.error;phys.abund.Fefloatnullable