J/AJ/151/40ivo://CDS.VizieR/J/AJ/151/40doi:10.26093/cds/vizier.51510040CDSBond H.E.Ciardullo R.Siegel M.H.2017-06-12T08:25:09Z2016-07-12T12:42:00ZCDS support team

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

cds-question@unistra.frglobular-star-clustersvariable-starsvisible-astronomybroad-band-photometryWe report the discovery of a luminous F-type post-asymptotic-giant-branch (PAGB) star in the Galactic globular cluster (GC) M79 (NGC 1904). At visual apparent and absolute magnitudes of V=12.20 and M_V_=-3.46, this "yellow" PAGB star is by a small margin the visually brightest star known in any GC. It was identified using CCD observations in the uBVI photometric system, which is optimized to detect stars with large Balmer discontinuities, indicative of very low surface gravities. Follow-up observations with the SMARTS 1.3 and 1.5m telescopes show that the star is not variable in light or radial velocity, and that its velocity is consistent with cluster membership. Near- and mid-infrared observations with 2MASS and WISE show no evidence for circumstellar dust. We argue that a sharp upper limit to the luminosity function exists for yellow PAGB stars in old populations, making them excellent candidates for Population II standard candles, which are four magnitudes brighter than RR Lyrae variables. Their luminosities are consistent with the stars being in a PAGB evolutionary phase, with core masses of ~0.53M_{sun}_. We also detected four very hot stars lying above the horizontal branch ("AGB-manque" stars); along with the PAGB star, they are the brightest objects in M79 in the near-ultraviolet. In the Appendix, we give periods and light curves for five variables in M79: three RR Lyrae stars, a Type II Cepheid, and a semiregular variable.2016AJ....151...40Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/151/40CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)VII/202 : Globular Clusters in the Milky Way (Harris, 1997)J/A+A/548/A92 : VrI light curves of NGC1904 variables (Kains+, 2012)J/MNRAS/370/1979 : JHKs photometry of T2Cs in globular clustersJ/A+AS/144/5 : Nearby globular clusters photometric catalogJ/A+AS/125/1 : The globular cluster NGC 1904 (Kravtsov+ 1997)J/AJ/107/230 : BVRI CCD photometry of NGC 1904 (Alcaino+, 1994)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/151/40https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/151/40http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/151/40https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/151/40https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/151/40http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/151/40GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/151/40/table5Differential photometry of variable stars in M79Band[BV] Band used in the observation (B or V)meta.code;instr.filtercharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarM79 variable star identifier (V6, V7, V8, V13, or V14)meta.id;meta.maincharHJDHeliocentric Julian Date (HJD-2450000)dtime.epochdoublemag[0.6/5.17] Differential photometry in Band (1)magphot.magfloatJ/AJ/151/40/table4Elements for M79-V6recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintYear0Starting year of seasonyrtime.epochintYear1? Ending year of seasonyrtime.epochintnullableT0Heliocentric Julian Date at zero phase T_0_ (HJD-2450000)dtime.epochdoublePerPerioddtime.perioddoubleJ/AJ/151/40/table3M79 variables in our 1.3m monitoring fieldTypeStar typesrc.classcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarM79 variable star identifiermeta.id;meta.maincharNpSimbad column added by the CDSmeta.numberintnullableT0? Heliocentric Julian Date at zero phase T_0_ (HJD-2450000)dtime.epochdoublenullablef_T0See Table 4 for seasonal elementsmeta.codecharPer? Perioddtime.perioddoublenullablef_PerSee Table 4 for seasonal elementsmeta.codecharIPer? Period interval for V8dtime.periodcharLCLight Curvemeta.ref.urlchar