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J/A+A/609/A13       Star cluster Gaia 1 stars equivalent widths    (Koch+, 2018)

Detailed chemical abundance analysis of the thick disk star cluster Gaia 1. Koch A., Hansen T., Kunder A. <Astron. Astrophys. 609, A13 (2018)> =2018A&A...609A..13K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Spectroscopy ; Equivalent widths Keywords: stars: abundances - Galaxy: abundances - Galaxy: structure - open clusters and associations: individual: Gaia 1 - Galaxy: disk - globular clusters Abstract: Star clusters, particularly those objects in the disk-bulge-halo interface are as yet poorly charted, despite the fact that they carry important information about the formation and the structure of the Milky Way. Here, we present a detailed chemical abundance study of the recently discovered object Gaia 1. Photometry has previously suggested it as an intermediate-age, moderately metal-rich system, although the exact values for its age and metallicity remained ambiguous in the literature. We measured detailed chemical abundances of 14 elements in four red giant members, from high-resolution (R=25000) spectra that firmly establish Gaia 1 as an object associated with the thick disk. The resulting mean Fe abundance is -0.62±0.03(stat.)±0.10(sys.) dex, which is more metal-poor than indicated by previous spectroscopy from the literature, but it is fully in line with values from isochrone fitting. We find that Gaia 1 is moderately enhanced in the α-elements, which allowed us to consolidate its membership with the thick disk via chemical tagging. The cluster's Fe-peak and neutron-capture elements are similar to those found across the metal-rich disks, where the latter indicate some level of s-process activity. No significant spread in iron nor in other heavy elements was detected, whereas we find evidence of light-element variations in Na, Mg, and Al. Nonetheless, the traditional Na-O and Mg-Al (anti-)correlations, typically seen in old globular clusters, are not seen in our data. This confirms that Gaia 1 is rather a massive and luminous open cluster than a low-mass globular cluster. Finally, orbital computations of the target stars bolster our chemical findings of Gaia 1's present-day membership with the thick disk, even though it remains unclear which mechanisms put it in that place. Description: Observations of four candidate members were taken during four nights in March 2017 using the Echelle spectrograph at the 2.5-m du Pont telescope at the Las Campanas Observatory, Chile, with a seeing of 0.7"-1.0" throughout the nights. Our spectroscopic set-up included a 1.0" slit with 2x1 binning in spectral and spatial dimensions, resulting in a resolving power of R∼25000. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 84 4 Observing log and target properties table2.dat 65 250 Line list
See also: J/A+A/565/A23 : Abundances of NGC5897 red giants (Koch+, 2014) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1 I1 --- Star Star sequential number 3- 4 I2 h RAh Rigth ascension (J2000.0) 6- 7 I2 min RAm Rigth ascension (J2000.0) 9- 13 F5.2 s RAs Rigth ascension (J2000.0) 15 A1 --- DE- Declination sign (J2000.0) 16- 17 I2 deg DEd Declination (J2000.0) 19- 20 I2 arcmin DEm Declination (J2000.0) 22- 26 F5.2 arcsec DEs Declination (J2000.0) 28- 33 F6.3 mag Jmag J magnitude 35- 40 F6.3 mag Hmag H magnitude 42- 47 F6.3 mag Kmag K magnitude 49- 59 A11 "date" Obs.Date Date of observation 61- 66 A6 s texp Exposure time 68- 69 I2 --- SN6550 Signal-to-noise ration measured at 6550Å 71- 72 I2 --- SN5500 Signal-to-noise ration measured at 5500Å 74- 75 I2 --- SN4500 Signal-to-noise ration measured at 4500Å 77- 80 F4.1 km/s HV Heliocentric velocity 82- 84 F3.1 km/s e_HV rms uncertainty on HV
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 4 F4.1 --- Ion Ion designation 8- 14 F7.2 0.1nm lambda Wavelength 19- 22 F4.2 eV EP Excitation potential 26- 32 F7.3 [-] loggf Oscillator strength 38- 40 I3 10-13m EW1 ? Equivalent width for Star 1 (1) 41 A1 --- n_EW1 [s] s for syn 46- 48 I3 10-13m EW2 ? Equivalent width for Star 2 (1) 49 A1 --- n_EW2 [s] s for syn 54- 56 I3 10-13m EW3 ? Equivalent width for Star 3 (1) 57 A1 --- n_EW3 [s] s for syn 62- 64 I3 10-13m EW4 ? Equivalent width for Star 4 (1) 65 A1 --- n_EW4 [s] s for syn
Note (1): In milli-Angstroms.
Acknowledgements: Andreas Koch, a.koch1(at)lancaster.ac.uk
(End) Patricia Vannier [CDS] 25-Sep-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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