J/ApJ/816/70ivo://CDS.VizieR/J/ApJ/816/70doi:10.26093/cds/vizier.18160070CDSFerraro F.R.Lapenna E.Mucciarelli A.Lanzoni B.Dalessandro E.,Pallanca C.Massari D.2017-10-12T13:00:22Z2016-04-08T13:15:35ZCDS support team

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

cds-question@unistra.frline-intensitiesglobular-star-clustersradial-velocityinfrared-photometryvisible-astronomyphotometryGlobular clusters are known to host peculiar objects named blue straggler stars (BSSs), significantly heavier than the normal stellar population. While these stars can be easily identified during their core hydrogen-burning phase, they are photometrically indistinguishable from their low-mass sisters in advanced stages of the subsequent evolution. A clear-cut identification of these objects would require the direct measurement of the stellar mass. We used the detailed comparison between chemical abundances derived from neutral and from ionized spectral lines as a powerful stellar "weighing device" to measure stellar mass and to identify an evolved BSS in 47Tucanae. In particular, high-resolution spectra of three bright stars, located slightly above the level of the "canonical" horizontal branch (HB) sequence in the color-magnitude diagram of 47 Tucanae, have been obtained with the UVES spectrograph. The measurements of iron and titanium abundances performed separately from neutral and ionized lines reveal that two targets have stellar parameters fully consistent with those expected for low-mass post-HB objects, while for the other target the elemental ionization balance is obtained only by assuming a mass of ~1.4M_{sun}_, which is significantly larger than the main sequence turn-off mass of the cluster (~0.85M_{sun}_). The comparison with theoretical stellar tracks suggests that this is a BSS descendant possibly experiencing its core helium-burning phase. The large applicability of the proposed method to most of the globular clusters in our Galaxy opens the possibility to initiate systematic searches for evolved BSSs, thus giving access to still unexplored phases of their evolution.2016ApJ...816...70Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/816/70CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/202 : Globular Clusters in the Milky Way (Harris, 1997)J/MNRAS/443/2492 : {Delta}a observations of 3 GCs (Paunzen+, 2014)J/A+A/572/A108 : 47 Tuc red giants chemical composition (Thygesen+, 2014)J/ApJ/780/94 : Abundances of red giants in 47 Tuc (Cordero+, 2014)J/A+A/550/A34 : Abundances of red giants in M4 and 47 Tuc (Carretta+, 2013)J/A+A/549/A41 : Horizontal branch stars in 47 Tuc and M5 (Gratton+, 2013)J/A+A/537/A2 : 8.6um imaging of 47 Tuc (Momany+, 2012)J/A+A/524/A44 : CN and CH line strengths in 12 globulars (Pancino+, 2010)J/A+A/517/A81 : 2nd & 3d param. of HB of globular clusters (Gratton+, 2010)J/MNRAS/405/839 : Spectroscopic obs. of globular clusters (Sharina+, 2010)J/A+A/505/139 : Abundances of red giants in 17 GCs (Carretta+, 2009)J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)J/MNRAS/383/183 : CaII triplet of RGB from VLT/FLAMES obs. (Battaglia+, 2008)J/AJ/135/1551 : Abundances of stars in 47 Tuc (Koch+, 2008)J/AJ/134/1298 : CaII equivalent widths in 29 GCs (Carrera+, 2007)J/ApJS/166/249 : Stellar dynamics & proper motions in 47Tuc (McLaughlin+, 2006)J/A+A/435/657 : Equivalent widths of 5 giants in 47 Tuc (Alves-Brito+, 2005)J/ApJ/625/796 : X-ray sources in the globular cluster 47 Tuc (Heinke+, 2005)J/AJ/130/2140 : Abundances and velocities in globular clusters (Pritzl+, 2005)J/AJ/130/1693 : HST-ACS observations of 5 globular clusters (Brown+, 2005)J/AJ/127/1588 : 47 Tuc main-sequence star abundances (Briley+, 2004)J/A+A/391/945 : HST photometry of 74 galactic GCs (Piotto+, 2002)J/A+AS/128/19 : Variable stars in 47 Tuc fields 104A-E (Kaluzny+ 1998)J/A+AS/113/299 : Abundances and velocities for cluster giants (Minniti 1995)J/ApJS/93/161 : CCD photometry of 6 globular clusters (Sarajedini+ 1994)J/PASP/99/739 : BV photometry in 4 fields of 47 Tuc (Hesser+, 1987)http://www.cosmic-lab.eu/Cosmic-Lab : Cosmic-Lab project home pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/816/70https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/816/70http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/816/70https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/816/70https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/816/70http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/816/70GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/816/70/table1 (Observational parameters of the three targets)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/816/70/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/816/70/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/816/70/table1?GETtext/xml+votable180.050000true6.0601164-72.07265280.0055555555555555566/33321https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/816/70?format=asciiInfraredOpticaldefaultJ/ApJ/816/70/table1Observational parameters of the three targetsNameStar namemeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1090214/2625792] ID numbermeta.idintRAJ2000[5.93/6.1] Righ ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[-72.11/-72] Declination (J2000)degpos.eq.dec;meta.mainVmag[13.5/13.8] V-band magnitudemagphot.mag;em.opt.VfloatV-I[0.92/0.98] V-I color indexmagphot.color;em.opt.V;em.opt.Ifloatr[42.1/132.2] Distance from the center (1)arcsecpos.angDistancefloatTeff[4896/5013] Effective temperatureKphys.temperature.effectiveintRVel[-24.3/-7.8] Radial velocitykm/sphys.veloc;pos.heliocentricfloate_RVel[0.05/0.06] RVel uncertaintykm/sstat.error;spect.dopplerVelocfloatEWsDislay the Equivalent Widths from table 2meta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/ApJ/816/70/table2Adopted line listrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambda[4834.5/6750.2] Wavelength; in Angstroms0.1nmem.wldoubleElElemental species identification (FeI, FeII, TiI or TiII)meta.id;phys.molcharExPot[0/5] Excitation potentialeVphys.atmol.excitationfloatlog(gf)[-5.6/0.7] Log of the oscillator strengthphys.atmol.oscStrengthfloatE-BSS1[0/162.2] Equivalent width of E-BSS1 (1)1e-13mspect.line.eqWidthfloatbHB1[0/150.2] Equivalent width of bHB1 (1)1e-13mspect.line.eqWidthfloatbHB2[0/169.5] Equivalent width of bHB2 (1)1e-13mspect.line.eqWidthfloat