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J/AJ/118/1245   Elemental abundances in five stars in M54  (Brown+, 1999)

Elemental abundances in five stars in M54, a globular cluster associated with the Sagittarius galaxy Brown J.A., Wallerstein G., Gonzalez G. <Astron. J. 118, 1245 (1999)> =1999AJ....118.1245B
ADC_Keywords: Abundances ; Clusters, globular Keywords: globular clusters: individual (M54) - stars: abundances Abstract: Chemical abundances in five stars in M54, a globular cluster associated with the Sagittarius dwarf galaxy, have been determined using high-resolution echelle spectra. We find the cluster to have [Fe/H] = -1.55 and possibly halo-normal abundance patterns, although the [O/Fe] and [α/Fe] ratios lie between solar and the normal halo values. One star shows the combination of low oxygen and enhanced Na and Al, symptomatic of deep mixing of ON-cycle and other proton-capture products; a second star shows a lesser degree of O depletion unaccompanied by Na and Al excesses. In the cluster Eu is also enhanced, indicating that about 30% of the Ba in the cluster is due to the r-process. In general, M54 is similar to globulars of comparable metallicity in the inner Galactic halo, despite its clear association with the Sagittarius dwarf spheroidal. Description: The observations were taken in two different observing runs with the CTIO 4 m telescope and Cassegrain echelle spectrograph, with a Loral 3K CCD as a detector, with the 31.6 lines mm-1 grating, air Schmidt camera, and 226-3 cross disperser grating. The configuration yields a resolving power λ/δλ = 24,000 and a spectral coverage of 5500 - 9000 Å. Objects: ----------------------------------------- RA (2000) DE Designation(s) ----------------------------------------- 18 55 18 -30 28 18 Ibata 1 18 52 02 -30 34 33 Ibata 2 18 54 56 -30 28 48 Ibata 10 18 55 02 -30 28 22 Ibata 11 18 54 56 -30 28 47 Ibata 13 ----------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 83 142 Line data for the Ibata stars
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Ion Ion name 8- 11 F4.2 --- Abd Log Ion's solar number abundance (H=12) 14- 20 F7.2 0.1nm Wave Wavelength of Ion 24- 28 F5.2 eV ExPot Excitation potential 30- 35 F6.2 --- log(gf) Log of the oscillator strength 37- 41 F5.1 10-4nm EqWI1 ? Equivalent width for star Ibata 1 (in mÅ) 43 A1 --- f_EqWI1 [a] Flag on EqWI1 (1) 45- 48 A4 --- n_EqWI1 Special limit on EqWI1 (≤ indicates less than or equal to) 49- 53 F5.1 10-4nm EqWI2 ? Equivalent width for star Ibata 2 (in mÅ) 55 A1 --- f_EqWI2 [a] Flag on EqWI2 (1) 57 A1 --- l_EqWI2 Limit on EqWI2 58- 62 F5.1 10-4nm EqWI10 ? Equivalent width for star Ibata 10 (in mÅ) 64 A1 --- f_EqWI10 [a] Flag on EqWI10 (1) 67- 71 F5.1 10-4nm EqWI11 ? Equivalent width for star Ibata 11 (in mÅ) 73 A1 --- f_EqWI11 [a] Flag on EqWI11 (1) 75 A1 --- l_EqWI11 Limit on EqWI11 76- 80 F5.1 10-4nm EqWI13 ? Equivalent width for star Ibata 13 (in mÅ) 82 A1 --- f_EqWI13 [ab] Flag on EqWI13 (1)
Note (1): a = Line too strong (log(W/λ) > -4.5) to be included in abundance solution b = The abundances from the Ba II lines of Ibata 13 are badly mutually discrepant, and we have no reason to accept one over any of the others; we accept no fit for Ba for Ibata 13
History: From AJ electronic edition.
(End) Greg Schwarz [AAS] 11-Apr-2000
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