J/ApJ/928/L11 Atmospheric param. of giants in omega Cen (Alvarez Garay+, 2022)
The Mg-K anticorrelation in ω Centauri.
Alvarez Garay D.A., Mucciarelli A., Lardo C., Bellazzini M., Merle T.
<Astrophys. J., 928, L11 (2022)>
=2022ApJ...928L..11A 2022ApJ...928L..11A
ADC_Keywords: Abundances; Spectra, optical; Radial velocities
Keywords: Chemical abundances
Abstract:
We present [K/Fe] abundance ratios for a sample of 450 stars in
ω Centauri, using high-resolution spectra acquired with the
multiobject spectrograph Abundances for Fe, Na, and Mg
were also derived. We detected intrinsic K variations in the analyzed
stars. Moreover, [K/Fe] shows a significant correlation with [Na/Fe]
and an anticorrelation with [Mg/Fe]. The presence of a clear-cut Mg-K
anticorrelation makes ω Centauri the third stellar system, after
NGC 2419 and NGC 2808, hosting a subpopulation of stars with
[Mg/Fe]<0.0dex, K-enriched in the case of ω Centauri by ∼0.3dex
with respect to Mg-rich stars ([Mg/Fe]>0.0dex). The
correlation/anticorrelation between K and other light elements
involved in chemical anomalies supports the idea that the spread in
[K/Fe] can be associated with the same self-enrichment process typical
of globular clusters. We suggest that significant variations in K
abundances perhaps can be found in the most massive and/or metal-poor
globular clusters as a manifestation of an extreme self-enrichment
process. Theoretical models face problems explaining K production in
globular clusters. Indeed, models where asymptotic giant branch stars
are responsible for the Mg-K anticorrelation only qualitatively agree
with the observations. Finally, we discovered a peculiar star with an
extraordinary K overabundance ([K/Fe]=+1.60dex) with respect to the
other stars with similar [Mg/Fe]. We suggest that this K-rich star
could be formed from the pure ejecta of AGB stars before dilution with
pristine material.
Description:
Observations were performed with the multiobject spectrograph FLAMES,
within the ESO program 095.D-0539 (P.I. Mucciarelli). We used FLAMES
in the GIRAFFE mode that allows us to allocate simultaneously up to
132 fibers. All the targets were observed with both HR11 and HR18
setups, covering the wavelength range from 5597 to 5840Å and from
7648 to 7889Å, and with a spectral resolution of 29500 and 20150,
respectively.
We selected targets among the member stars of ω Centauri already
analyzed in previous works (Norris & Da Costa 1995ApJ...447..680N 1995ApJ...447..680N ;
Johnson & Pilachowski 2010, J/ApJ/722/1373 and
Marino+ 2011, J/ApJ/731/64).
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
13 26 47.28 -47 28 46.1 ω Centauri = * ome Cen
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 90 440 Data for the analysed targets in ω Centauri
--------------------------------------------------------------------------------
See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010)
J/ApJ/731/64 : Spectroscopy of 300 RGBs in ω Cen (Marino+, 2011)
J/ApJ/760/86 : Equivalent widths for 13 NGC2419 RGB stars (Cohen+, 2012)
J/MNRAS/450/815 : Red giants in NGC 5286 (Marino+, 2015)
J/AJ/149/153 : Abundances of red giants in 10 GCs (Meszaros+, 2015)
J/A+A/600/A104 : K abundance in 3 globular clusters (Mucciarelli+, 2017)
J/A+A/601/A112 : GES iDR4 Mg-Al anticorrelation in GCs (Pancino+, 2017)
J/MNRAS/478/1520 : Milky Way globular clusters data (Baumgardt+, 2018)
J/A+A/616/A10 : Open clusters GaiaDR2 HR diagrams (Gaia Collaboration, 2018)
J/A+A/627/A177 : Non-LTE analysis of K I in late-type stars (Reggiani+, 2019)
J/MNRAS/492/1641 : APOGEE southern GCs with the BACCHUS code (Meszaros+, 2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- ID Identifier (1)
12- 18 F7.4 mag Gmag [10.69/14.4] Gaia EDR3 G band magnitude
20- 25 F6.2 km/s RVel [191/277] Radial velocity
27- 30 I4 K Teff [3934/5283] Effective temperature
32- 34 I3 K e_Teff [85/147] Uncertainty in Teff
36- 39 F4.2 [cm/s2] log(g) [0.4/2.5] log surface gravity
41- 44 F4.2 km/s vt [1.5/2.1] Microturbulent velocity
46- 50 F5.2 [-] [Fe/H] [-2.2/-0.5] log Fe/H abundance ratio
52- 55 F4.2 [-] e_[Fe/H] [0.05/0.2] Uncertainty in [Fe/H]
57- 61 F5.2 [-] [Na/Fe] [-0.42/0.6]?=99.99 log Na/Fe abundance ratio
63- 67 F5.2 [-] e_[Na/Fe] [0.03/0.2]?=99.99 Uncertainty in [Na/Fe]
69- 73 F5.2 [-] [Mg/Fe] [-0.5/0.7]?=99.99 log Mg/Fe abundance ratio
75- 79 F5.2 [-] e_[Mg/Fe] [0.02/0.21]?=99.99 Uncertainty in [Mg/Fe]
81- 85 F5.2 [-] [K/Fe] [-0.2/1.6] log K/Fe abundance ratio
87- 90 F4.2 [-] e_[K/Fe] [0.05/0.2] Uncertainty in [K/Fe]
--------------------------------------------------------------------------------
Note (1): In ID, references are:
NDC = Norris & Da Costa 1995ApJ...447..680N 1995ApJ...447..680N (12 occurrences;
in Simbad)
J10 = Johnson & Pilachowski 2010, J/ApJ/722/1373 (346 occurrences;
<Cl* NGC 5139 LEID NNNNN> in Simbad)
M11 = Marino+ 2011, J/ApJ/731/64 (82 occurrences;
<[MMP2011] RGB NNN> or <Cl* NGC 5139 WFI NNNNNN> in Simbad)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Mar-2024