2022A&A...666A.177C


Query : 2022A&A...666A.177C

2022A&A...666A.177C - Astronomy and Astrophysics, volume 666A, 177 (2022/10-1)

Multiple stellar populations in the high-temperature regime: Potassium abundances in the globular cluster M 54 (NGC 6715).

CARRETTA E.

Abstract (from CDS):

Among the multiple stellar populations in globular clusters (GCs) the very high-temperature H-burning regime, able to produce elements up to potassium, is still poorly explored. Here we present the first abundance analysis of K in 42 giants of NGC 6715 (M 54) with homogeneous abundances of light elements previously derived in our FLAMES survey. Owing to the large mass and low metallicity, a large excess of K could be expected in this GC, which is located in the nucleus of the Sagittarius dwarf galaxy. We actually found a spread in [K/Fe] spanning about 1 dex, with [K/Fe] presenting a significant anti-correlation with [O/Fe] ratios, regardless of the metallicity component in M 54. Evidence for a K-Mg anti-correlation also exists, but this is statistically marginal because of the lack of very Mg-poor stars in this GC. We found, however, a strong correlation between K and Ca. These observations clearly show that the K enhancement in M 54 is probably due to the same network of nuclear reactions generating the phenomenon of multiple stellar populations, at work in a regime of very high temperature. The comparison with recent results in ω Cen is hampered by an unexplained trend with the temperatures for K abundances from optical spectroscopy, and somewhat by a limited sample size for infrared APOGEE data. There are few doubts, however, that the two most massive GCs in the Milky Way host a K-Mg anti-correlation.

Abstract Copyright: © E. Carretta 2022

Journal keyword(s): stars: abundances - stars: atmospheres - stars: Population II - globular clusters: general - globular clusters: individual: NGC 6715

Simbad objects: 12

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Number of rows : 12
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 M 79 GlC 05 24 10.59 -24 31 27.3     8.16     ~ 819 0
2 NGC 2419 GlC 07 38 08.51 +38 52 54.9     10.05     ~ 935 0
3 NGC 2808 GlC 09 12 03.10 -64 51 48.6           ~ 1424 0
4 NGC 4833 GlC 12 59 33.92 -70 52 35.4           ~ 426 0
5 NGC 5139 GlC 13 26 47.28 -47 28 46.1           ~ 3433 0
6 M 80 GlC 16 17 02.41 -22 58 33.9           ~ 719 0
7 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 2119 0
8 NGC 6388 GlC 17 36 17.461 -44 44 08.34           ~ 917 1
9 M 54 GlC 18 55 03.33 -30 28 47.5           ~ 1071 0
10 NAME SDG G 18 55 19.0 -30 32 43   4.5 3.6     ~ 2195 2
11 M 55 GlC 19 39 59.71 -30 57 53.1     6.49     ~ 857 0
12 M 15 GlC 21 29 58.33 +12 10 01.2           ~ 3143 0

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