J/AJ/149/66ivo://CDS.VizieR/J/AJ/149/66doi:10.26093/cds/vizier.51490066CDSNgeow C.-C.Lee C.-H.Yang M.T.-C.Lin C.-S.Hsiao H.-Y.Cheng Y.-C.,Lin Z.-Y.Lin I.-L.Kanbur S.M.Ip W.-H.2018-01-30T07:18:08Z2015-02-27T10:39:05ZCDS support team

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

cds-question@unistra.frgalaxiesvariable-starsinfrared-photometryvisible-astronomyphotometryThe ultra-long-period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding ~80days. The intrinsic brightness of ULPCs are ~1 to ~3mag brighter than their shorter period counterparts. This makes them attractive in future distance scale work to derive distances beyond the limit set by the shorter period Cepheids. We have initiated a program to search for ULPCs in M31, using the single-band data taken from the Palomar Transient Factory, and identified eight possible candidates. In this work, we presented the VI-band follow-up observations of these eight candidates. Based on our VI-band light curves of these candidates and their locations in the color-magnitude diagram and the Period-Wesenheit diagram, we verify two candidates as being truly ULPCs. The six other candidates are most likely other kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the applicability of ULPCs in distance scale work by deriving the distance modulus of M31. It was found to be {mu}_M31,ULPC_=24.30+/-0.76mag. The large error in the derived distance modulus, together with the large intrinsic dispersion of the Period-Wesenheit (PW) relation and the small number of ULPCs in a given host galaxy, means that the question of the suitability of ULPCs as standard candles is still open. Further work is needed to enlarge the sample of calibrating ULPCs and reduce the intrinsic dispersion of the PW relation before re-considering ULPCs as suitable distance indicators.2015AJ....149...66Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/149/66CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)J/ApJ/799/144 : M31 Cepheids in near-IR (Kodric+, 2015)J/AJ/145/106 : M31 Cepheid disk sample of 1st year of PS1 (Kodric+, 2013)J/ApJ/745/156 : M31 Cepheids with HST/WFC3 (Riess+, 2012)J/ApJ/743/19 : M31 variable star candidates photometry (Clementini+, 2011)J/AcA/59/239 : Light curves of LMC long-period variables (Soszynski+, 2009)J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)J/A+A/459/321 : BV photometry of M31 eclipsing binaries (Vilardell+, 2006)J/A+A/445/423 : WeCAPP Survey. M31 variables (Fliri+, 2006)J/MNRAS/351/1071 : POINT-AGAPE Survey. M31 variables (An+, 2004)J/A+A/421/509 : AGAPE catalogue of M31 variables (Ansari+, 2004)J/A+A/402/113 : (RI)c photometry of variables in M31 (Joshi+, 2003)J/AJ/126/175 : M31Y eclipsing binaries and Cepheids (Bonanos+, 2003)J/AJ/118/2211 : M31F eclipsing binaries and Cepheids (Mochejska+ 1999)J/AJ/118/346 : M31D eclipsing binaries and Cepheids (Kaluzny+ 1999)J/AJ/117/2810 : Eclipsing binaries and Cepheids in M31C (Stanek+, 1999)J/AJ/115/1894 : Eclipsing binaries and Cepheids in M31A field (Stanek+ 1998)J/AJ/115/1016 : M31B eclipsing binaries and Cepheids (Kaluzny+ 1998)J/A+AS/126/401 : M31 Cepheids periods (Magnier+ 1997)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/149/66https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/149/66http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/149/66https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/149/66https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/149/66http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/149/66GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/149/66/table3 (Revised periods and mean magnitudes for the candidates)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/149/66/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/149/66/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/149/66/table3?GETtext/xml+votable180.050000true10.6326583341.486297220.0055555555555555566/2623 2667 2708 2709https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/149/66?format=asciiOpticalInfrareddefaultJ/AJ/149/66/table2VI-band light curves for the candidatesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintULPCInternal identifier for the Ultra-Long-Period Cepheid candidate (G1)meta.id;meta.maincharprimaryTelTelescope used in the observation (LOT or P60) (1)instr.setup;obscharBand[VI] Bandpass used in the observationinstr.filter;obscharMJDModified Julian Date of the observationdtime.epoch;obsdoublemag[17.0/21.2] Observed magnitude in Bandmagphot.mag;instr.filter;obsfloate_magError in magmagstat.error;phot.mag;instr.filterfloatJ/AJ/149/66/table3Revised periods and mean magnitudes for the candidatesLCLight Curvesmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintf_ULPCClass of ULPC: C=M31 ULPC candidate, NC=M31 non-ULPC candidate)meta.codecharULPCInternal identifier for the Ultra-Long-Period Cepheid candidate (G1)meta.id;meta.maincharprimaryPerPerioddtime.periodfloate_PerUncertainty in Perdstat.errorfloat<Vmag>Mean V band magnitudemagphot.mag;em.opt.Vfloat<Imag>Mean I band magnitudemagphot.mag;em.opt.IfloatWmagExtinction-free Wesenheit magnitude, defined as W=I-1.55(V-I) (1)magphot.color.reddFreefloatRAJ2000Hour of Right Ascension (J2000) (2)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000) (2)pos.eq.dec;meta.mainSimbadSimbad name (2)meta.idchar