Chemical Composition of Intermediate-Mass Star Members of the M6 (Ngc 6405) Open Cluster

Abstract

We present here the first abundance analysis of 44 late B, A and F-type members of the young open cluster M6 (NGC 6405, age about 75 Myrs). Low and medium resolution spectra, covering the 4500 to 5800Å wavelength range, were obtained using the FLAMES/GIRAFFE spectrograph attached to the ESO Very Large Telescopes (VLT). We determined the atmospheric parameters using calibrations of the Geneva photometry and by adjusting the H β profiles to synthetic ones. The abundances of up to 20 chemical elements, from helium to mercury, were derived for 19 late B, 16 A and 9 F stars by iteratively adjusting synthetic spectra to the observations. We also derived a mean cluster metallicity of [Fe/H] = 0.07 ± 0.03 dex from the iron abundances of the F-type stars . We find that, for most chemical elements, the normal late B and A-type stars exhibit larger star-to-star abundance variations than the F-type stars do probably because of the faster rotation of the B and A stars. The abundances of C, O, Mg, Si and Sc appear to be anticorrelated to that of Fe, while the opposite holds for the abundances of Ca, Ti, Cr, Mn, Ni, Y, and Ba about as expected if radiative diffusion is efficient in the envelopes of these stars. In the course of this analysis, we discovered five new peculiar stars: one mild-Am, one Am, and one Fm star (HD 318091, CD-32 13109, GSC 07380-01211), one HgMn star (HD 318126), and one He-weak P-rich (HD 318101) star. We also discovered a new spectroscopic binary, most likely a SB2. We performed a detailed modelling of HD 318101,the new He-weak P-rich CP star, using the Montréal stellar evolution code XEVOL which treats self-consistently all particle transport processes. Although the overall abundance pattern of this star is properly reproduced, we find that detailed abundances (in particular the high P excess) resisted modelling attempts even when a range of turbulence profiles and mass loss rates were considered. Solutions -4are proposed, which are still under investigation. Subject headings: stars: abundances -open clusters: individual(M6) -stars individual: HD 318101stars in open clusters, with a variety of goals (Stütz et al. 2006;Villanova et al. 2009;Pace et al. 2010;Pancino et al. 2010; Jacobson et al. 2011;Carrera & Pancino 2011;Carraro et al. 2014).In this paper, we present the first abundance analysis of 44 late B, A and F-type dwarfs members of the young open cluster M6. M6 (NGC 6405) is an interarm object lying between the local arm and the Sagittarius arm (Vleeming 1974). It is a moderately-rich cluster (van den Bergh & Hagen 1975) and it contains about 120 most-likely members (for V ≤ 15.1) according to Antalová (1972). Previous age, distance, color excess and metallicity determinations for the cluster are collected in Table 1, along with our determinations (see Sec. 4.1.2 and 2.1). Early estimates of the distance, reddening and age of the cluster were obtained photometrically by Rohlfs et al. (1959) 1 who derived a distance of 630 pc from photoelectric UBV observations of 132 stars, a mean reddening E(B...

A spectroscopic study of the open cluster NGC 6250

“…After comparison between abundance and each of the fundamental parameters, we see no statistically significant patterns. This is consistent with the findings of Kılıçoglu et al (2016).…”

SPCANet: Stellar Parameters and Chemical Abundances Network for LAMOST-II Medium Resolution Survey

“…Same as Fig.10 but density distribution of elemental abundances for LAMOST MRS giants. The white scatters are values from the previous literature (Masseron et al 2019;Donor et al 2018;Kovalev et al 2019;Magrini et al 2017;Kılıçoglu et al 2016;Tautvaišienė et al 2015;Mishenina et al 2011;Bensby et al 2014;Zhao et al 2016;Nissen 2016). (Bensby et al 2014) studied 714 F and G dwarfs and subgiants in the Solar neighborhood and determined their stellar parameters and elemental abundances based on high-resolution spectra.…”

“…We cross-match our results with GALAH DR2 and get 396 common stars corresponding 1021 LAMOST-II MRS spectra after setting "flag cannon=0" in GALAH parameter catalog. (Masseron et al 2019;Donor et al 2018;Kovalev et al 2019;Magrini et al 2017;Kılıçoglu et al 2016;Tautvaišienė et al 2015;Mishenina et al 2011;Bensby et al 2014;Zhao et al 2016;Nissen 2016).…”

Metallicity calibrations for dwarf stars and giants in the Geneva photometric system

“…Table A1). We note that the result by Kılıçoglu et al (2016) for the latter object was not considered in the comparison in Sect. 4.1 owing to the adopted criteria.…”