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J/A+A/534/A53  Equivalent widths of 18 subgiant of ω Cen  (Pancino+, 2011)

The subgiant branch of omega Cen seen through high-resolution spectroscopy. II. The most metal-rich population. Pancino E., Mucciarelli A., Bonifacio P., Monaco L., Sbordone L. <Astron. Astrophys. 534, A53 (2011)> =2011A&A...534A..53P
ADC_Keywords: Clusters, globular ; Stars, giant ; Stars, population II ; Equivalent widths Keywords: stars: abundances - globular clusters: individual: omega Centauri Abstract: We analyze spectra of 18 stars belonging to the faintest subgiant branch in omega Centauri (the SGB-a), obtained with GIRAFFE@VLT at a resolution of R~=17000 and a S/N ratio between 25 and 50. We measure abundances of Al, Ba, Ca, Fe, Ni, Si, and Ti and we find that these stars have <[Fe/H]≥-0.73±0.14dex, similarly to the corresponding red giant branch population (the RGB-a). We also measure <[alpha/Fe]≥+0.40±0.16dex, and <[Ba/Fe]≥+0.87±0.23dex, in general agreement with past studies. It is very interesting to note that we found a uniform Al abundance, <[Al/Fe]≥+0.32±0.14dex, for all the 18 SGB-a stars analysed here, thus supporting past evidence that the usual (anti-)correlations are not present in this population, and suggesting a non globular cluster-like origin of this particular population. In the dwarf galaxy hypothesis for the formation of omega Cen, this population might be the best candidate for the field population of its putative parent galaxy, although some of its properties appear contradictory. It has also been suggested that the most metal-rich population in omega Cen is significantly enriched in helium. If this is true, the traditional abundance analysis techniques, based on model atmospheres with normal helium content, might lead to errors. We have computed helium enhanced atmospheres for three stars in our sample and verified that the abundance errors due to the use of non-enhanced atmospheres are negligible. Additional, indirect support to the enhanced helium content of the SGB-a population comes from our Li upper limits. Description: Equivalent widths and atomic data for all elements studied with a classical equivalent width analysis in the 18 omega Centauri subgiants studied. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 70 18 Observing Logs and atmospheric parameters table2.dat 52 589 Equivalent widths for 18 subgiants in ω Centauri
See also: J/MNRAS/357/265 : BVI photometry of omega Cen red giants (Sollima+, 2005) J/ApJ/661/L155 : Radial velocities Rgb stars in omega Cen (Pancino+, 2007) J/A+A/527/A18 : EW of 6 subgiants of ω Cen (Pancino+, 2011) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 6 I6 --- WFI WFI identification number, <Cl* NGC 5139 WFI NNNNNN> in Simbad 8- 12 I5 --- FORS FORS identification number (Sollima et al. 2005, Cat. J/MNRAS/357/265), <Cl* NGC 5139 SGP NNNNNN> in Simbad (1) 14- 24 F11.7 deg RAdeg Right ascension in decimal degrees (J2000) 26- 36 F11.7 deg DEdeg Declination in decimal degrees (J2000) 38- 42 F5.2 mag Vmag V magnitude (1) 44- 47 F4.2 mag (B-V)0 Deredenned B-V colour index (1) 49- 52 F4.2 mag (V-I)0 Deredenned V-I_J_ colour index (1) 54 I1 --- Nobs Number of observations 56- 57 I2 --- S/N Signal-to-noise ratio 59- 62 I4 K Teff Hα effective temperature 64- 66 F3.1 [cm/s2] logg Surface gravity 68- 70 F3.1 km/s vt Microturbulent velocity
Note (1): From Sollima et al., 2005, Cat. J/MNRAS/357/265
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 6 I6 --- WFI WFI identification number of subgiant 9- 15 F7.2 0.1nm lambda Wavelength in Angstroms 17- 20 A4 --- Ion Element name and ionization stage 22- 25 F4.2 eV EP Excitation potential 28- 32 F5.2 [-] loggf Logarithm of the oscillator strength 35- 39 F5.1 0.1pm EW Equivalent width in mÅ 42- 45 F4.1 0.1pm e_EW Formal DAOSPEC error on EW (in mÅ) 48- 52 F5.3 --- q_EW DAOSPEC Q parameter on EW
Acknowledgements: Elena Pancino, elena.pancino(at) References: Pancino et al., Paper I 2011A&A...527A..18P, Cat. J/A+A/527/A18
(End) E. Pancino [INAF, Bologna Obs., Italy], P. Vannier [CDS] 06-Sep-2011
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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