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J/A+A/601/A31          Reduced spectra of NGC 6528 stars            (Liu+, 2017)

Determination of robust metallicities for metal-rich red giant branch stars. An application to the globular cluster NGC 6528. Liu C., Ruchti G., Feltzing S., Primas F. <Astron. Astrophys. 601, A31 (2017)> =2017A&A...601A..31L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, normal ; Spectroscopy Keywords: Galaxy: bulge - globular clusters: individual: NGC 6528 - stars: atmospheres - stars: fundamental parameters Abstract: Here we explore robust ways of determining the iron content of metal-rich giant stars. We aim to understand what biases and shortcomings the widely applied methods suffer from. In this study we were mainly concerned with standard methods of analysing stellar spectra. These include the analysis of individual lines to determine stellar parameters, and analysis of the broad wings of certain lines (e.g. Halpha and calcium lines) to determine effective temperature and surface gravity for the stars. For NGC 6528 we find that [Fe/H]=+0.04dex with a scatter of 0.07dex, which gives an error in the derived mean abundance of 0.02dex. Our work has two important conclusions for analysis of metal-rich red giant branch stars. Firstly, for spectra with S/N of below about 35 per reduced pixel, [Fe/H] becomes too high. Secondly, determination of Teff using the wings of the Hα line results in [Fe/H] values about 0.1dex higher than if excitational equilibrium is used. The last conclusion is perhaps unsurprising, as we expect the NLTE effect to become more prominent in cooler stars and we can not use the the wings of the Hα line to determine Teff for the cool stars in our sample. We therefore recommend that in studies of metal-rich red giant stars care should be taken to obtain sufficient calibration data to enable use of the cooler stars. Description: The 1D spectra of globular cluster NGC 6528 stars could be directly used to measure stellar parameters and elemental abundances, and/or as benchmarks to calibrate metal-rich populations in bulge. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 121 75 Basic information for all stars analysed in this study list.dat 121 66 List of gfits spectra fits/* 0 66 Individual fits spectra
See also: J/AJ/84/1305 : UBV photometry in NGC 6528 (van den Bergh+, 1979) J/A+AS/127/167 : V,I CCD photometry of NGC 6528 (Richtler+ 1998) J/A+A/385/67 : NGC 6528 HST VI photometry & proper motions (Feltzing+, 2002) J/A+A/565/A8 : Stroemgren photometry near NGC 6528 (Calamida+, 2014) J/A+A/573/A13 : Metal abundances in 6 globular cluster (Dias+, 2015) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Seq [1/34] Sequential number of the source 4- 7 A4 --- ID Identification number of the source 9- 32 A24 --- Name Source name (2MASS or VVV) 34- 35 I2 h RAh Right ascension (J2000) 37- 38 I2 min RAm Right ascension (J2000) 40- 44 F5.2 s RAs Right ascension (J2000) 46 A1 --- DE- Declination sign (J2000) 47- 48 I2 deg DEd Declination (J2000) 50- 51 I2 arcmin DEm Declination (J2000) 53- 54 I2 arcsec DEs Declination (J2000) 56- 60 F5.2 mag Jmag0 ?=- De-reddened J magnitude (1) 62- 66 F5.2 mag Hmag0 ?=- De-reddened H magnitude (1) 68- 73 F6.3 mag Kmag0 ?=- De-reddened K magnitude (1) 75- 81 F7.2 km/s RV Radial velocity 83- 86 F4.2 km/s e_RV rms uncertainty on RV 87 A1 --- n_RV [c] Note on RV (2) 89- 98 A10 "date" Obs.Date Observation date 100-105 A6 s ExpTime Exposure time 107-117 A11 --- Inst Instrument 119-121 I3 --- S/N Signal-to-noise ratio measured from the spectrum (3)
Note (1): De-reddened magnitudes have been derived adopting the reddening law by Cardelli et al. (1989ApJ...345..245C). Note (2): c: The radial velocity is adopted from Carretta et al. (2001AJ....122.1469C). Note (3): The average S/N of the final co-added spectrum for each star was estimated using the SPLOT task within IRAF at three short wavelength regions (574.4-574.7nm, 604.7-606.3nm, and 606.8-607.6nm).
Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Seq [1/34] Sequentail number of the source 4- 8 I5 --- Nx Number of pixels along X-axis 10- 32 A23 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss.sss) 34- 40 F7.2 0.1nm blambda Lower value of wavelength interval 42- 48 F7.2 0.1nm Blambda Upper value of wavelength interval 50- 58 F9.7 0.1nm dlambda Resolution 60- 62 I3 Kibyte size Size of FITS file 64- 84 A21 --- FileName Name of FITS file, in subdirectory fits 86-121 A36 --- Title Title of the FITS file
Acknowledgements: Cheng Liu, cheng(at)astro.lu.se References: Zoccali et al., 2004A&A...423..507Z, Metal content of NGC 6528
(End) Cheng Liu [Lund Obs., Sweden], Patricia Vannier [CDS] 16-Feb-2017
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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