J/AJ/157/35ivo://CDS.VizieR/J/AJ/157/35doi:10.26093/cds/vizier.51570035CDSVivas A.K.Alonso-Garcia J.Mateo M.Walker A.Howard B.2021-04-09T07:02:51Z2019-05-31T09:35:36ZCDS support team

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

cds-question@unistra.frgalaxiesstellar-populationsvariable-starsdwarf-starsvisible-astronomysloan-photometrystellar-distanceA large extension of the Sextans dwarf spheroidal galaxy, 7 deg^2^, has been surveyed for variable stars using the Dark Energy Camera at the Blanco Telescope at Cerro Tololo Inter-American Observatory, Chile. We report seven anomalous Cepheids, 199 RR Lyrae stars, and 16 dwarf Cepheids in the field. This is only the fifth extragalactic system in which dwarf Cepheids have been systematically searched. Henceforth, the new stars increase the census of stars coming from different environments that can be used to asses the advantages and limitations of using dwarf Cepheids as standard candles in populations for which the metallicity is not necessarily known. The dwarf Cepheids found in Sextans have a mean period of 0.066 day and a mean g amplitude of 0.87 mag. They are located below the horizontal branch, spanning a range of 0.8 mag: 21.9<g<22.7. The number of dwarf Cepheids in Sextans is low compared with other galaxies such as Carina, which has a strong intermediate-age population. On the other hand, the number and ratio of RR Lyrae stars to dwarf Cepheids are quite similar to those of Sculptor, a galaxy which, as Sextans, is dominated by an old stellar population. The dwarf Cepheid stars found in Sextans follow a well-constrained period-luminosity relationship with an rms=0.05 mag in the g band, which was set up by anchoring to the distance modulus given by the RR Lyrae stars. Although the majority of the variable stars in Sextans are located toward the center of the galaxy, we have found two RR Lyrae stars and one anomalous Cepheid in the outskirts of the galaxy that may be extratidal stars and suggest that this galaxy may be undergoing tidal destruction. These possible extratidal variable stars share the same proper motions as Sextans, as seen by recent Gaia measurements. Two additional stars that we initially classified as foreground RR Lyrae stars may actually be other examples of Sextans extratidal anomalous Cepheids, although radial velocities are needed to prove that scenario.2019AJ....157...35Vhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/157/35CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)J/AJ/110/2166 : Variables in Sextans dSph galaxy (Mateo+ 1995)J/AJ/126/2840 : BVI CCD photometry of Sextans dSph galaxy (Lee+, 2003)J/AJ/137/3100 : Radial velocities of 4 dSph galaxies (Walker+, 2009)J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)J/MNRAS/411/1013 : CaII triplet in Sextans dSph galaxy (Battaglia+, 2011)J/MNRAS/460/30 : gi photometry of Sextans dSph galaxy stars (Roderick+, 2016)J/A+A/609/A53 : Tracing stars of MW dwarf galaxies: SextansJ/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)J/ApJ/855/43 : Distant RR Lyrae stars discovered with HiTS (Medina+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/157/35https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/157/35http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/157/35https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/157/35https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/157/35http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/157/35GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/157/35/table4 (Anomalous Cepheids)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/157/35/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/157/35/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/157/35/table4?GETtext/xml+votable180.050000true153.21128-1.642430.005555555555555556Cone search capability for table J/AJ/157/35/table2 (Dwarf Cepheid (DC) stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/157/35/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/157/35/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/157/35/table2?GETtext/xml+votable180.050000true152.37167-1.294720.005555555555555556Cone search capability for table J/AJ/157/35/table3 (RR Lyrae stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/157/35/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/157/35/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/157/35/table3?GETtext/xml+votable180.050000true152.06381-2.273720.0055555555555555565/6804 6/27205 27206 27207 27212 27213 27224https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/157/35?format=asciiOpticaldefaultJ/AJ/157/35/table4Anomalous CepheidsONameOther name (only in Table 4)meta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDIdentification number (DCNN or ACN)meta.id;meta.maincharRAJ2000Right Ascension in decimal degrees (J2000.0)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000.0)degpos.eq.dec;meta.maingmagmean[18.64/22.79] Mean magnitude in g-bandmagphot.mag;em.opt.Bfloato_gmag[32/48] Number of gmag observationsmeta.numberintrmagmean[18.55/22.8] Mean magnitude in r-bandmagphot.mag;em.opt.Rfloato_rmag[4/38] Number of rmag observationsmeta.numberintPer[0.0509/0.9198] Perioddtime.periodfloatgamp[0.08/1.14] The g-band amplitudemagsrc.var.amplitudefloatramp[0.37/0.84]? The r-band amplitudemagsrc.var.amplitudefloatnullableSimbadSimbad column added by the CDSmeta.ref.urlcharJ/AJ/157/35/table2Dwarf Cepheid (DC) starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDIdentification number (DCNN or ACN)meta.id;meta.maincharRAJ2000Right Ascension in decimal degrees (J2000.0)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000.0)degpos.eq.dec;meta.maingmagmean[18.64/22.79] Mean magnitude in g-bandmagphot.mag;em.opt.Bfloato_gmag[32/48] Number of gmag observationsmeta.numberintrmagmean[18.55/22.8] Mean magnitude in r-bandmagphot.mag;em.opt.Rfloato_rmag[4/38] Number of rmag observationsmeta.numberintPer[0.0509/0.9198] Perioddtime.periodfloatgamp[0.08/1.14] The g-band amplitudemagsrc.var.amplitudefloatramp[0.37/0.84]? The r-band amplitudemagsrc.var.amplitudefloatnullableDSex[3.1/60.5]? Distance to the center of Sextans (only in Table 2)arcminpos.angDistancefloatnullableComComment on membership (only in Table 2) (G1)meta.code.membercharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/AJ/157/35/table3RR Lyrae starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDIdentification number (RRNNN)meta.id;meta.maincharRAJ2000Right Ascension in decimal degrees (J2000.0)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000.0)degpos.eq.dec;meta.mainType[ab c d] Type of variablemeta.code;src.varcharPer[0.2799/0.7801]? Perioddtime.periodfloatnullableMJD0[56723.9974/57848.33177]? Modified Julian Date at maximum lightdtime.epochdoublenullablegamp[0.14/1.49]? The g-band amplitudemagsrc.var.amplitudefloatnullablegmagmean[18.05/20.83] Mean magnitude in g-bandmagphot.mag;em.opt.Bfloato_gmag[28/48] Number of gmag observationsmeta.numberintgmagmax[17.43/20.47]? Maximum magnitude in g-bandmagphot.mag;em.opt.B;stat.maxfloatnullablegsigfit[0.01/0.09]? rms of the template fit in g-bandmagphot.mag;meta.modelledfloatnullablegtempBest template fitted in g-band from Sesar et al. (2010, J/ApJ/708/717) librarymeta.id;meta.filecharramp[0.1/0.95]? The r-band amplitudemagsrc.var.amplitudefloatnullablermagmean[17.91/20.61] Mean magnitude in r-bandmagphot.mag;em.opt.Rfloato_rmag[2/38] Number of rmag observationsmeta.numberintrmagmax[17.54/20.26]? Maximum magnitude in r-bandmagphot.mag;em.opt.R;stat.maxfloatnullablersigfit[0.01/0.06]? rms of the template fit in r-bandmagstat.fit.residual;phot.mag;meta.modelledfloatnullablertempBest template fitted in r-band from Sesar et al. (2010, J/ApJ/708/717) librarymeta.id;meta.filecharONameOther name(s)meta.idcharComComment on membership (G1)meta.code.membercharSimbadSimbad column added by the CDSmeta.ref.urlchar