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J/A+A/527/A18       EW of 6 subgiants of ω Cen            (Pancino+, 2011)

The subgiant branch of omega Cen seen through high-resolution spectroscopy. I. The first stellar generation in omega Centauri? Pancino E., Mucciarelli A., Sbordone L., Bellazzini M., Monaco L., Ferraro F.R. <Astron. Astrophys. 527, A18 (2011)> =2011A&A...527A..18P
ADC_Keywords: Clusters, globular ; Stars, giant ; Stars, population II ; Equivalent widths Keywords: stars: abundances - stars: population II - stars: late-type - globular clusters: individual: omega Centauri - globular clusters: individual: NGC 6397 Abstract: We analysed high-resolution UVES spectra of six stars belonging to the subgiant branch of ω Centauri, and derived abundance ratios of 19 chemical elements (namely Al, Ba, C, Ca, Co, Cr, Cu, Fe, La, Mg, Mn, N, Na, Ni, Sc, Si, Sr, Ti, and Y). A comparison with previous abundance determinations for red giants provided remarkable agreement and allowed us to identify the sub-populations to which our targets belong. We found that three targets belong to a low-metallicity population at [Fe/H]=-2.0dex, [alpha/Fe]=+0.4dex and [s/Fe]=0dex. Stars with similar characteristics were found in small amounts by past surveys of red giants. We discuss the possibility that they belong to a separate sub-population that we name VMP (very metal-poor, at most 5% of the total cluster population), which - in the self-enrichment hypothesis - is the best-candidate first stellar generation in ω Cen. Two of the remaining targets belong to the dominant metal-poor population (MP) at [Fe/H]=-1.7dex, and the last one to the metal-intermediate (MInt) one at [Fe/H]=-1.2dex. The existence of the newly defined VMP population could help to understand some puzzling results based on low-resolution spectroscopy (Sollima et al. 2005ApJ...634..332S , Villanova et al., 2007, Cat. J/ApJ/663/296) in their age differences determinations, because the metallicity resolution of these studies was probably not enough to detect the VMP population. The VMP could also correspond to some of the additional substructures of the subgiant-branch region found in the latest HST photometry (Bellini et al., 2010, Cat. J/AJ/140/631). After trying to correlate chemical abundances with substructures in the subgiant branch of ω Cen, we found that the age difference between the VMP and MP populations should be small (0±2Gyr), while the difference between the MP and MInt populations could be slightly larger (2±2Gyr). Description: Equivalent widths and atomic data for all elements studied with a classical equivalent width analysis in the six ω Centauri subgiants studied. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 79 6 Observing logs table2.dat 146 507 Equivalent widths and atomic data
See also: J/ApJ/663/296 : omega Cen (NGC5139) subgiants UBV(RI)c phot. (Villanova+, 2007) J/AJ/135/1395 : omega Cen Spitzer photometry (Boyer+, 2008) J/A+A/493/959 : UBV(RI)cHalpha photometry in omega Cen (Bellini+, 2009) J/AJ/140/631 : HST WFC3/UVIS photometry of omega Cen core (Bellini+, 2010) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 6 I6 --- WFI WFI identification number of subgiant 8- 17 F10.6 deg RAdeg Right ascension (J2000) 19- 28 F10.6 deg DEdeg Declination (J2000) 30- 34 F5.2 mag Vmag V magnitude 36- 39 F4.2 mag (B-V)0 Deredenned B-V colour index 41- 44 F4.2 mag (V-I)0 Deredenned V-I colour index 46- 50 I5 --- R Resolution (λ/{dlta}λ ratio) 52- 56 I5 s Texp Exposure time 58- 59 I2 --- S/N Signal-to-noise ratio at 550nm 61- 65 F5.1 km/s RV Radial velocity 67- 69 F3.1 km/s e_RV rms uncertainty on RV 71- 79 A9 --- Notes Notes
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 7 F7.2 0.1nm lambda Wavelength in Angstroms 10- 13 A4 --- Ion Element name and ionization stage 16- 19 F4.2 eV EP Excitation potential 22- 26 F5.2 [-] loggf Logarithm of the oscillator strength 29- 33 F5.1 0.1pm W503358 ?=0 Equivalent width of star WFI 503358 (1) 36- 39 F4.1 0.1pm e_W503358 ?=0 formal error on W503358 (in mAA) (1) 42- 46 F5.3 --- q_W503358 ?=0 DAOSPEC Q parameter for star WFI 503358 (1) 49- 53 F5.1 0.1pm W503951 ?=0 Equivalent width of star WFI 503951 (1) 56- 59 F4.1 0.1pm e_W503951 ?=0 formal error on W503951 (in mAA) (1) 62- 66 F5.3 --- q_W503951 ?=0 DAOSPEC Q parameter for star WFI 503951 (1) 69- 73 F5.1 0.1pm W507109 ?=0 Equivalent width of star WFI 507109 (1) 76- 79 F4.1 0.1pm e_W507109 ?=0 formal error on W507109 (in mAA) (1) 82- 86 F5.3 --- q_W507109 ?=0 DAOSPEC Q parameter for star WFI 507109 (1) 89- 93 F5.1 0.1pm W507633 ?=0 Equivalent width of star WFI 507633 (1) 96- 99 F4.1 0.1pm e_W507633 ?=0 formal error on W507633 (in mAA) (1) 102-106 F5.3 --- q_W507633 ?=0 DAOSPEC Q parameter for star WFI 507633 (1) 109-113 F5.1 0.1pm W512115 ?=0 Equivalent width of star WFI 512115 (1) 116-119 F4.1 0.1pm e_W512115 ?=0 formal error on W512115 (in mAA) (1) 122-126 F5.3 --- q_W512115 ?=0 DAOSPEC Q parameter for star WFI 512115 (1) 129-133 F5.1 0.1pm W512938 ?=0 Equivalent width of star WFI 512938 (1) 136-139 F4.1 0.1pm e_W512938 ?=0 formal error on W512938 (in mAA) (1) 142-146 F5.3 --- q_W512938 ?=0 DAOSPEC Q parameter for star WFI 512938 (1)
Note (1): A value of zero in EW, EW error and Q parameter means that a line was not measured or not used for the abundance analysis of that star. The quality parameter Q measures the deviations from a gaussian line, and is high (Q>1) for problematic lines (introduced by Stetson & Pancino 2008PASP..120.1332S)
Acknowledgements: Elena Pancino, elena.pancino(at)oabo.inaf.it
(End) Elena Pancino [INAF-OABo, Italy], Patricia Vannier [CDS] 22-Dec-2010
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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