Comprehensive abundance analysis of red giants in the open clusters NGC 752, 1817, 2360 and 2506

Abstract

We have analysed high‐dispersion echelle spectra (R ≳ 50 000) of red giant members for four open clusters to derive abundances for many elements. The spread in temperatures and gravities being very small among the red giants nearly the same stellar lines were employed thereby reducing the random errors. The errors of average abundance for the cluster were generally in the range 0.02–0.07 dex. Our present sample covers Galactocentric distances of 8.3–10.5 kpc. The [Fe/H] values are −0.02 ± 0.05 for NGC 752, −0.07 ± 0.06 for NGC 2360, −0.11 ± 0.05 for NGC 1817 and −0.19 ± 0.06 for NGC 2506. Abundances relative to Fe for elements from Na to Eu are equal within measurement uncertainties to published abundances for thin‐disc giants in the field. This supports the view that field stars come from disrupted open clusters.

The evolution of the Milky Way: new insights from open clusters

“…The chemical abundances for the individual cluster members averaged over all available lines of given species are presented in Tables 3−12 8 , relative to solar abundances derived from the adopted gf -values (see Table 4 from Reddy et al 2012). Table entries (2015), we evaluated the impact of stellar parameters (T eff , log g, ξt) on the derived abundances and the abundance differences caused by the variation of each stellar parameter with respect to the best model parameter are summed in quadrature to obtain a global uncertainty σ2.…”

“…Following the precepts discussed in Reddy et al (2012), we derived the star's effective temperature, T phot eff⋆ , by substituting the dereddened 6 optical and 2MASS photometric colors (B-V), (V-Ks) and (J-Ks) into the infrared flux method metallicity-dependent color−temperature calibrations of Alonso et al (1999).…”

“…The surface gravities, log g, were computed by incorporating the known distance to the OCs, T phot eff⋆ , bolometric correction BCV , cluster turn-off mass M⋆ and the solar values of T eff ,⊙= 5777 K and log g⊙= 4.44 cm s −2 into the well known log g − T eff relation (Reddy et al 2012). Estimates of BCV s were made using Alonso et al's (1999) relation connecting the photometric T eff⋆ s and metallicities.…”

“…We have presented in our previous papers (Reddy et al 2012(Reddy et al , 2013(Reddy et al , 2015 abundance measurements for 16 OCs with ages from 130 Myr to 4.3 Gyr and Rgcs from 8.3 and 11.3 kpc. We combine our sample of twenty-eight OCs (12 from this study and 16 from our previous papers) with a sample of 51 OCs drawn from the literature for which we have remeasured the chemical content using their published EWs, our models, linelists and reference solar abundances to establish a common abundance scale.…”

Comprehensive abundance analysis of red giants in the open clusters NGC 1342, 1662, 1912, 2354 and 2447

“…In our first paper (Reddy et al 2012, hereafter paper I) we have presented abundance measurements for four open clusters (OCs) whose Galactocentric distances (Rgc) lie between 8.3 and 10.5 kpc, where the Sun's Galactocentric distance is taken as 8.0±0.6 kpc (Ghez et al 2008). Here, we add seven OCs six of which have not previously analysed in detail also in the Galactic anticentre direction in the disc.…”