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

Abstract

We have analyzed high-resolution echelle spectra of red giant members for seven open clusters in the Galactic anticentre direction to explore their chemical compositions. Cluster membership has been confirmed by radial velocity. The spread in temperatures and gravities being very small among the red giants, nearly the same stellar lines were employed for all stars thereby reducing the abundance errors: the errors of the average abundance for a cluster were generally in the 0.02 to 0.05 dex range. Our present sample covers Galactocentric distances of 8.3 to 11.3 kpc and an age range of 0.2 to 4.3 Gyr. A careful comparison of our results for the cluster NGC 2682 (M 67) to other high-resolution abundance studies in the literature shows general good agreement for almost all elements in common.

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

“…Systematic offsets between chemical abundances of OCs collected from different resources and our sample of 28 OCs are negligible as we have remeasured the chemical content of all 51 OCs drawn from the literature using their published EWs, our models, linelists and reference solar abundances. The chemical abundances of 51 OCs are presented previously in Table 13 from Reddy et al (2015). Stars in our sample and those drawn from the literature are similar red giants analysed identically and, thus, systematic errors affecting the abundances and abundance ratios [X/Fe] should be consistent (and small) across the sample which spans a narrow range in metallicity of ∼ −0.5 to 0.3 dex but a good range in ages and Galactocentric distances.…”

“…6 The adopted interstellar extinctions are (A V , A K , E(V-K), E(J-K))= (3.1, 0.28, 2.75, 0.54)*E(B-V), where E(B-V) is taken from WEBDA We performed a differential abundance analysis relative to the Sun by running the abfind driver of MOOG 7 adopting the 1D model atmospheres and the iron line equivalent widths (EWs) following the local thermodynamic equilibrium (LTE) abundance analysis technique described in Reddy et al (2015). The line EWs for a selected sample of clean, unblended, isolated and symmetric spectral lines of various atomic/ionic species were measured manually using routines in IRAF while avoiding the wavelength regions affected by telluric contamination and heavy line crowding.…”

“…The line EWs for a selected sample of clean, unblended, isolated and symmetric spectral lines of various atomic/ionic species were measured manually using routines in IRAF while avoiding the wavelength regions affected by telluric contamination and heavy line crowding. We prepared a linelist of 300 absorption lines covering 23 elements from Na-Eu in the spectral range 4450−8850Å, as described in Reddy et al (2015). The model atmospheres were interpolated linearly from the ATLAS9 model atmosphere grid of Castelli & Kurucz (2003).…”

“…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.…”

“…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. Useful data on chemical composition of the literature sample is presented previously in Table 13 from Reddy et al (2015). This paper is organized as follows: In Section 2 we describe observations, data reduction and radial velocity measurements.…”