2014A&A...566A..39C


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST01:38:36

2014A&A...566A..39C - Astronomy and Astrophysics, volume 566A, 39-39 (2014/6-1)

Updated properties of the old open cluster Melotte 66: Searching for multiple stellar populations.

CARRARO G., DE SILVA G., MONACO L., MILONE A.P. and MATELUNA R.

Abstract (from CDS):

Multiple generations of stars are routinely encountered in globular clusters but no convincing evidence has been found in Galactic open clusters to date. In this paper, we use new photometric and spectroscopic data to search for multiple stellar population signatures in the old, massive open cluster, Melotte 66. The cluster is known to have a red giant branch wide in color, which could be an indication of metallicity spread. Also the main sequence is wider than what is expected from photometric errors only. This evidence might be associated with either differential reddening or binaries. Both hypothesis have, however, to be evaluated in detail before recurring to the presence of multiple stellar populations. New, high-quality, CCD UBVI photometry have been acquired to this aim with high-resolution spectroscopy of seven clump stars that are complemented with literature data; this doubles the number of clump star members of the cluster for which high-resolution spectroscopy is available. All this new material is carefully analyzed in search for any spectroscopic or photometric manifestation of multiple populations among the cluster stars. Our photometric study confirms that the width of the main sequence close to the turn off point is entirely accounted for by binary stars and differential reddening with no need to advocate more sofisticated scenarios, such as metallicity spread or multiple main sequences. By constructing synthetic color-magnitude diagrams, we infer that the binary fraction has to be as large as 30% and their mass ratio in the range 0.6-1.0. As a by-product of our simulations, we provide new estimates of the cluster fundamental parameters. We measure a reddening E(B-V)=0.15±0.02, and confirm the presence of a marginal differential reddening. The distance to the cluster is 4.7+0.2–0.1kpc and the age is 3.4±0.3Gyr, which is somewhat younger and better constrained than previous estimates. Our detailed abundance analysis reveals that, overall, Melotte 66 looks like a typical object of the old thin disk population with no significant spread in any of the chemical species we could measure. Finally, we perform a photometric study of the blue straggler star population and argue that their number in Melotte 66 has been significantly overestimated in the past. The analysis of their spatial distribution supports the scenario that they are most probably primordial binaries.

Abstract Copyright:

Journal keyword(s): stars: abundances - open clusters and associations: general - Galaxy: disk

VizieR on-line data: <Available at CDS (J/A+A/566/A39): table2.dat>

Status at CDS:   All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 18

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Number of rows : 18

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 188 OpC 00 48 26 +85 15.3           ~ 813 0
2 IC 1805 OpC 02 32 42 +61 27.0   7.03 6.5     ~ 473 2
3 NGC 1783 GlC 04 59 08.590 -65 59 15.84   10.9 10.93     ~ 226 0
4 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14826 1
5 C 0634+094 OpC 06 36 29 +09 28.2     10.9     ~ 73 0
6 SA 98- reg 06 52 04.1 -00 23 58           ~ 164 0
7 NGC 2324 OpC 07 04 07 +01 02.7   8.83 8.4     ~ 124 0
8 Cl Melotte 66 OpC 07 26 23 -47 40.0   8.73 7.8     ~ 170 0
9 Cl Berkeley 39 OpC 07 46 42 -04 36.0           ~ 152 1
10 NGC 2477 OpC 07 52 10 -38 31.8   6.64 5.8     ~ 256 0
11 IRAS 09110-6439 GlC 09 12 03.10 -64 51 48.6   7.77 5.69     ~ 1244 0
12 NAME Sextans C GlC 10 05 30.96 +00 04 15.4   15.5 13.9     ~ 290 1
13 Cl Collinder 261 OpC 12 38 11.5 -68 22 01     10.7     ~ 156 0
14 C 1235-509 GlC 12 38 40.20 -51 09 01.0           ~ 322 0
15 Cl Terzan 7 GlC 19 17 43.92 -34 39 27.8           ~ 359 0
16 NGC 6791 OpC 19 20 53 +37 46.3   10.52 9.5     ~ 869 0
17 Cl Terzan 8 GlC 19 41 44.41 -33 59 58.1     11.54     ~ 256 0
18 NAME Galactic Bulge reg ~ ~           ~ 3387 0

    Equat.    Gal    SGal    Ecl

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2020.07.04-01:38:36

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