SIMBAD references

2012ApJ...754...91L - Astrophys. J., 754, 91 (2012/August-1)

Chemical and kinematical properties of blue straggler stars and horizontal branch stars in NGC 6397.

LOVISI L., MUCCIARELLI A., LANZONI B., FERRARO F.R., GRATTON R., DALESSANDRO E. and CONTRERAS RAMOS R.

Abstract (from CDS):

We used three sets of high-resolution spectra acquired with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to investigate the chemical and kinematical properties of a sample of 42 horizontal branch (HB) stars, 18 blue straggler stars (BSSs), and 86 main-sequence (MS) turnoff (TO) and sub-giant branch stars in the nearby globular cluster NGC 6397. We measured rotational velocities and Fe, O, and Mg abundances. All of the unevolved stars in our sample have low rotational velocites (vsin i < 10 km/s), while the HB stars and BSSs show a broad distribution, with values ranging from 0 to ∼70 km/s. For HB stars with T < 10,500 K there is a clear temperature-oxygen anticorrelation that can be understood if the star position along the HB is mainly determined by the He content. The hottest BSSs and HB stars (with temperatures T > 8200 K and T > 10,500 K, respectively) also show significant deviations in their iron abundance with respect to the cluster metallicity (as traced by the unevolved stars, [Fe/H] = -2.12). While similar chemical patterns have already been observed in other hot HB stars, this is the first evidence ever collected for BSSs. We interpret these abundance anomalies as due to the metal radiative levitation, occurring in stars with shallow or no convective envelopes.

Abstract Copyright:

Journal keyword(s): blue stragglers - globular clusters: individual: NGC 6397 - stars: abundances - stars: evolution - techniques: spectroscopic

VizieR on-line data: <Available at CDS (J/ApJ/754/91): table2.dat table3.dat table4.dat>

Nomenclature: Tables 2-4: [LML2012] NNNNNNN N=146

Status at CDS:  

Simbad objects: 156

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2020.03.29-18:20:19

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