J/A+A/707/A322 Abundances of alpha-elements in 16 GCs (Carretta, 2026)
Homogenous abundances of Mg, Si, Ca, and Ti for about 1500 red giants in 16
globular clusters from FLAMES spectra.
Carretta E.
<Astron. Astrophys. 707, A322 (2026)>
=2026A&A...707A.322C 2026A&A...707A.322C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, giant ; Stars, population II ;
Abundances ; Optical
Keywords: stars: abundances - stars: atmospheres - stars: population II -
globular clusters: general
Abstract:
The FLAMES survey "Na-O anti-correlation and HB" uncovered the modern
standard for globular clusters (GCs), that is their ubiquitous
multiple stellar populations (MPs) distinct by the abundance of
proton-capture elements. That survey can still be mined to extract a
wealth of data. We derive new abundances of Mg, Si, Ca, and Ti for
948, 954, 1542, and 1350 red giant branch stars in 16 GCs, both formed
in situ or accreted in the Milky Way. The program GCs cover the
metallicity range from [Fe/H]=-2.35dex to [Fe/H]=-0.74dex. Both the
halo and disc GCs show a clear overabundance of alpha-elements with
the modulation in Mg and Si due to the MPs phenomenon in different
clusters. We found star to star variations in Si abundance correlated
to changes in Na in more than half of our sample, implying that
temperatures in excess of about 65 MK were achieved in the polluters
responsible for the enrichment. We confirm with an enlarged sample the
previous result that significant variations in Mg are observed in GCs
that are metal-poor, massive or both. Evidence of excess of Ca with
respect to reference unpolluted field stars are found in NGC 6752 and
NGC 7078, indicating the action of proton-capture reactions at very
high temperature regime in these GCs. These excesses fit very well in
a previously found relation as a function of a combination of cluster
mass and metallicity shown by other typical signatures of MPs. At odds
with previous results based on the Si abundance from APOGEE, we found
that the average abundance of alpha-elements is not an efficient
discriminating factor between in situ and accreted GCs.
Description:
Abundances of alpha-elements Mg, Si, Ca, TiI and TiII for individual
red giants in 16 globular clusters: NGC 104, NGC 288, NGC 1904,
NGC 3201, NGC 4590, NGC 5904, NGC 6121, NGC 6171, NGC 6218, NGC 6254,
NGC 6397, NGC 6752, NGC 6809, NGC 6838, NGC 7078, NGC 7099
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea.dat 110 1769 Abundances of alpha elements in stars of 16 GCs
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See also:
J/A+A/505/139 : Abundances of red giants in 17 globular clusters
(Carretta+, 2009)
J/ApJ/712/L21 : Calcium abundances in 17 globular clusters (Carretta+, 2010)
J/ApJ/750/L14 : Abundances of red giants in NGC 6752 (Carretta+, 2012)
J/A+A/550/A34 : Abundances of red giants in M4 and 47 Tuc (Carretta+, 2013)
Byte-by-byte Description of file: tablea.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- NGC NGC cluster number
6 A1 --- Flag [UG] star with UVES (U) or GIRAFFE (G)
spectra (1)
8- 16 F9.5 deg RAdeg Right ascension (J2000.0) of star
18- 26 F9.5 deg DEdeg Declination (J2000.0) of star
29 I1 --- o_Mg ? Number of Mg lines
31- 36 F6.3 --- [Mg/Fe] ? Abundance [Mg/Fe]
39- 43 F5.3 --- e_[Mg/Fe] ? rms uncertainty on [Mg/Fe]
45- 46 I2 --- o_Si ? Number of Si lines
49- 53 F5.3 --- [Si/Fe] ? Abundance [Si/Fe]
55- 59 F5.3 --- e_[Si/Fe] ? rms uncertainty on [Si/Fe]
61- 62 I2 --- o_Ca ? Number of Ca lines
65- 69 F5.3 --- [Ca/Fe] ? Abundance [Ca/Fe]
71- 75 F5.3 --- e_[Ca/Fe] ? rms uncertainty on [Ca/Fe]
77- 78 I2 --- o_TiI ? Number of TiI lines
81- 86 F6.3 --- [TiI/Fe] ? Abundance [Ti/Fe]I
89- 93 F5.3 --- e_[TiI/Fe] ? rms uncertainty on [Ti/Fe]I
95- 96 I2 --- o_TiII ? Number of TiII lines
100-104 F5.3 --- [TiII/Fe] ? Abundance [Ti/Fe]II
106-110 F5.3 --- e_[TiII/Fe] ? rms uncertainty on [Ti/Fe]II
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Note (1): Mg and Si for all U stars are from Carretta et al.,
2009A&A...505..139C 2009A&A...505..139C, Cat. J/A+A/505/139
Ca for all U stars are from Carretta et al., 2010ApJ...712L..21C 2010ApJ...712L..21C,
Cat. J/ApJ/712/L21
Mg and Si for G stars in NGC 104 and NGC 6121 are from
Carretta et al., 2013A&A...550A..34C 2013A&A...550A..34C, cat. J/A+A/550/A34
Mg and Si for G stars in NGC 6752 are from
Carretta et al., 2012ApJ...750L..14C 2012ApJ...750L..14C, Cat. J/ApJ/750/L14
For convenience, they are reported here together with the other elements
for all stars.
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Acknowledgements:
Eugenio Carretta, eugenio.carretta(at)inaf.it
(End) Patricia Vannier [CDS] 29-Jan-2026