2004A&A...424..951P


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.14CEST17:02:04

2004A&A...424..951P - Astronomy and Astrophysics, volume 424, 951-963 (2004/9-4)

Detailed chemical composition of the open cluster IC 4651: The iron peak, α elements, and Li.

PASQUINI L., RANDICH S., ZOCCALI M., HILL V., CHARBONNEL C. and NORDSTROEM B.

Abstract (from CDS):

We present a detailed chemical analysis of 22 stars along the colour-magnitude sequence of the intermediate-age (1.7Gyr) open cluster IC 4651, based on high-resolution, high S/N ratio spectra from UVES/VLT. IC 4651 thus becomes one of the few open clusters for which a detailed composition analysis exists for stars spanning 3.5mag, from solar-type main-sequence stars to giants above the RGB clump. In a strict comparison with the Sun, we find for the cluster a well-defined Fe abundance of [Fe/H]=0.10±0.03 (internal errors), with a reddening E(b-y)=0.091. We also derive abundances for the α elements Mg, Si, Ti, and Ca and find a moderate enhancement of the three former elements, in excellent agreement with the results for field stars of similar Fe abundance. Among the Fe group elements, Cr and Ni are slightly overabundant ([X/Fe]∼0.05). As also observed in M 67, the Na abundance among the giants is more than 0.2dex higher than in the dwarfs. We interpret this effect as real, and due to dredge-up of 23Na in the giants. Four turnoff stars, all fairly rapid rotators (vsini≥25km/s), appear to have higher [Fe/H] than the other stars; our tests show that, while a spurious enhancement of 0.1dex can be produced by the effect of high rotation on our spectral analysis, this cannot explain the whole difference. These stars appear overabundant because we tend to overestimate their effective temperatures by forcing excitation equilibrium. Li abundances have been computed for all the stars and show a well-defined pattern: the Solar-type stars have an almost constant Li abundance, just below that of the Hyades, and the Li-dip is pronounced and well determined. Turnoff stars just above the dip have a ``cosmic'' Li abundance, but within a very small range of magnitudes (0.25mag) higher on the turnoff, the Li level drops by more than a factor 10. This cannot be due just to dilution; rather some extra mixing is required. Among the giants, two probable clump stars show detectable Li, while all the other (likely) RGB stars do not - as is also observed in the similar cluster NGC 3680. None of these patterns can be explained by classical stellar evolution models. Again, some extra mixing is required. We show that rotating stellar models including the most recent developments for meridional circulation and turbulence by shear instabilities explain very well the behaviour of the lithium abundance along the colour-magnitude diagram of IC 4651, including subgiant and giant phases. The possibility remains open that the giants exhibiting the highest lithium abundances are actual RGB bump stars which have just been through the so-called ``lithium flash".

Abstract Copyright:

Journal keyword(s): stars: abundances - Galaxy: open clusters and associations: individual: IC 4651 - stars: evolution - stars: rotation

CDS comments: Tables: T812 or E812 is the same star 'IC 4651 812' in SIMBAD.

Simbad objects: 26

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Number of rows : 26

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 752 OpC 01 57 41 +37 47.1           ~ 538 0
2 NGC 3680 OpC 11 25 38 -43 14.6   8.40 7.6     ~ 290 0
3 IC 4651 199 * 17 24 30.8884919902 -50 00 53.694721993   12.66 12.061     ~ 13 0
4 IC 4651 200 * 17 24 31.9672049907 -49 59 43.224503929   14.12 13.55     ~ 11 0
5 IC 4651 201 * 17 24 32.4190803619 -49 59 20.677899697   13.66 13.117     ~ 11 0
6 IC 4651 95 * 17 24 36.8673353386 -49 55 54.691175424   13.473 12.937     ~ 12 0
7 IC 4651 109 * 17 24 37.5542584853 -49 57 51.524626175   14.10 13.424     ~ 10 0
8 IC 4651 202 * 17 24 38.2693719145 -49 59 47.236150261   13.18 12.618     ~ 7 0
9 CD-49 11401 * 17 24 41.5352500573 -49 59 06.472606126   11.401 10.363     ~ 26 0
10 IC 4651 174 * 17 24 42.0637178257 -49 53 02.417010159   12.99 12.381     ~ 12 0
11 IC 4651 208 * 17 24 45.0587259439 -50 00 52.256260918   13.45 12.832     ~ 10 0
12 IC 4651 77 * 17 24 46.0311708359 -49 54 51.049145684   14.09 13.53 13.48   ~ 12 0
13 CD-49 11402 * 17 24 46.7175582312 -49 54 06.990074317   12.027 10.894     ~ 27 0
14 IC 4651 26 * 17 24 48.2600006414 -49 56 37.110790149   14.293 13.699     ~ 10 0
15 IC 4651 OpC 17 24 49 -49 56.0           ~ 309 0
16 IC 4651 29 * 17 24 49.4896781310 -49 57 26.934679880   12.03 10.90     K0III 24 0
17 IC 4651 211 * 17 24 52.5647446485 -50 01 03.497853024   14.93 14.28     ~ 12 0
18 IC 4651 22 * 17 24 52.5925891435 -49 56 31.358109070   12.23 11.37     ~ 13 0
19 CD-49 11410 * 17 24 57.7598325878 -50 01 32.957880075   11.89 10.78     ~ 21 0
20 IC 4651 5 * 17 25 00.25 -49 56 38.1   14.653 14.022     ~ 10 0
21 IC 4651 64 * 17 25 01.2734927328 -49 53 52.902180624   12.81 11.989     ~ 14 0
22 IC 4651 812 * 17 25 03.0269849598 -50 04 17.562257079   12.01 11.09     ~ 11 0
23 IC 4651 131 * 17 25 06.2286493972 -49 59 49.963544598   12.97 12.256     ~ 13 0
24 IC 4651 52 * 17 25 12.7200674261 -49 54 55.749748495   14.43 13.743     ~ 10 0
25 IC 4651 43 * 17 25 14.2401467688 -49 56 43.667985114   14.89 14.193     ~ 18 0
26 IC 4651 142 * 17 25 18.3153652775 -49 58 10.235454744   13.22 12.685     ~ 12 0

    Equat.    Gal    SGal    Ecl

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2020.08.14-17:02:04

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