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J/AJ/154/150      Spectroscopy of RGB stars in ω Centauri      (An+, 2017)

Medium-resolution spectroscopy of red giant branch stars in ω Centauri. An D., Lee Y.S., Jung J.In, Rey S.-C., Rhee J., Lee J.-W., Lee Y.-W., Joe Y.H. <Astron. J., 154, 150 (2017)> =2017AJ....154..150A (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, giant ; Spectroscopy ; Abundances ; Effective temperatures ; Radial velocities Keywords: globular clusters: individual (omega Centauri) - stars: abundances Abstract: We present [Fe/H] and [Ca/Fe] of ∼600 red giant branch (RGB) members of the globular cluster Omega Centauri (ω Cen). We collect medium-resolution (R∼2000) spectra using the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory equipped with Hydra, the fiber-fed multi-object spectrograph. We demonstrate that blending of stellar light in optical fibers severely limits the accuracy of spectroscopic parameters in the crowded central region of the cluster. When photometric temperatures are taken in the spectroscopic analysis, our kinematically selected cluster members, excluding those that are strongly affected by flux from neighboring stars, include relatively fewer stars at intermediate metallicity ([Fe/H]~-1.5) than seen in the previous high-resolution survey for brighter giants in Johnson & Pilachowski (2010, J/ApJ/722/1373). As opposed to the trend of increasing [Ca/Fe] with [Fe/H] found by those authors, our [Ca/Fe] estimates, based on Ca II H & K measurements, show essentially the same mean [Ca/Fe] for most of the metal-poor and metal-intermediate populations in this cluster, suggesting that mass- or metallicity-dependent SN II yields may not be necessary in their proposed chemical evolution scenario. Metal-rich cluster members in our sample show a large spread in [Ca/Fe], and do not exhibit a clear bimodal distribution in [Ca/Fe]. We also do not find convincing evidence for a radial metallicity gradient among RGB stars in ω Cen. Description: We selected spectroscopic targets among RGB stars in ω Cen based on a BV color-magnitude diagram (CMD) of Rey et al. (2004, J/AJ/127/958). We collected medium-resolution spectra using the Blanco 4 m telescope equipped with Hydra at the Cerro Tololo Inter-American Observatory (CTIO). The Hydra is a fiber-fed multi-object spectrograph with 138 large optical fibers, each of which has a ∼300 µm diameter or a ∼2" aperture on a focal plane. We observed ω Cen in 11 different fiber configurations on UT 2005 May 27 and 28. In this study, we present spectroscopic parameters of 712 stars (including cluster non-members) for which there exist at least one spectrum, with a signal-to-noise ratio (S/N) equal to or greater than 52 per resolution elements at 4500=<λ(Å)=<5500. Objects: ------------------------------------------------------- RA (ICRS) DE Designation(s) ------------------------------------------------------- 13 26 47.28 -47 28 46.1 omega Centauri = NGC 5139 ------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 108 712 Spectroscopic Properties of Stars in ω Cen
See also: J/ApJ/462/241 : Ca abundance for Omega Cen red giants (Norris+ 1996) J/AJ/127/958 : CCD BV photometry on Omega Cen (Rey+, 2004) 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/ApJ/681/1505 : Abundances of red giants in ω Cen (Johnson+, 2008) J/MNRAS/396/2183 : Radial velocities of red giants in ω Cen (Sollima+ 2009) J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010) J/ApJ/731/64 : Spectroscopy of 300 RGBs in ω Cen (Marino+, 2011) J/MNRAS/416/L6 : AGB and RGB stars in ω Cen (McDonald+, 2011) J/MNRAS/427/1153 : Stellar parameters of giants in ω Cen (Simpson+, 2012) J/MNRAS/433/1892 : Abundances of 848 giants of ω Cen (Simpson+, 2013) J/ApJ/837/176 : Spectroscopic obs. of 2 red giant stars in omega Cen (Yong+, 2017) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq [1/712] Sequential running star identifier 5- 6 I2 h RAh Hour of Right Ascension (J2000) 8- 9 I2 min RAm Minute of Right Ascension (J2000) 11- 15 F5.2 s RAs Second of Right Ascension (J2000) 17 A1 --- DE- Sign of the Declination (J2000) 18- 19 I2 deg DEd Degree of Declination (J2000) 21- 22 I2 arcmin DEm Arcminute of Declination (J2000) 24- 28 F5.2 arcsec DEs Arcsecond of Declination (J2000) 30- 35 F6.3 mag Vmag [14.201/14.998] V band magnitude from Rey et al. 2004 (J/AJ/127/958) 37- 41 F5.3 mag B-V [0.802/1.281] B-V color from Rey et al. 2004 (J/AJ/127/958) 43- 46 I4 K Teff [4601/5410] Adjusted IRFM (Infrared Flux Method) effective temperature 48- 50 I3 K e_Teff [0/107]?=-99 Uncertainty in Teff 53- 56 F4.2 [cm/s2] logg [0.5/4.04] Surface gravity 58- 62 F5.2 [cm/s2] e_logg [0/1.49]?=-9.99 Uncertainty in logg 64- 68 F5.2 [-] [Fe/H] [-2.28/0.21] Metallicity 70- 74 F5.2 [-] e_[Fe/H] [0/1.54]?=-9.99 Uncertainty in [Fe/H] 76- 80 F5.2 [-] [Ca/Fe] [-1.87/1.19] Calcium abundance 82- 86 F5.2 [-] e_[Ca/Fe] [0.01/0.72]?=-9.99 Uncertainty in [Ca/Fe] 88- 93 F6.1 km/s RV [-89.6/286.9]?=-999.9 Radial velocity 95- 98 F4.1 km/s e_RV [0/60.4]?=-9.9 Uncertainty in RV 100-104 F5.2 --- Fneighb [0/0.98]?=-9.99 Fractional contribution of flux in B passband from neighboring stars 106 I1 --- Nobs [1/3] Number of spectra with S/N≥52 108 A1 --- Mem [mx] Cluster membership (1)
Note (1): Cluster membership, based on radial velocities and proper motions, is defined as follows: m = Cluster member; x = Non-member.
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 10-Jul-2018
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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