HAL will be down for maintenance from Friday, June 10 at 4pm through Monday, June 13 at 9am. More information
Skip to Main content Skip to Navigation
Journal articles

NGC 6397: The metallicity trend along the isochrone revisited

Abstract : Context. Recent work has used spectra of ∼5000 stars in NGC 6397 that were extracted from a MUSE mosaic to determine the atmospheric parameters for these stars by fitting the spectra against the Göttingen Spectral Library. A significant change in metallicity between the turn off and the red giant branch was found and was discussed as a possible manifestation of predicted effects of atomic diffusion. However, the small amplitude of the effect and inconsistency with earlier measurements call for more attention before this result is interpreted. Systematic effects due to the interpolation or to the synthetic spectra cannot be ruled out at this level of precision. Aims. We reanalyze the data with : the ELODIE and MILES reference libraries in order to assess the robustness of the result. These empirical libraries have a finer metallicity coverage down to approximately the cluster metalicity turn-off. Methods. We used the ULySS full-spectrum fitting package, together with the library interpolators to remeasure the three atmospheric parameters effective temperature, surface gravity, and [Fe/H] metallicity. Results. We find a very low [Fe/H] dispersion along the isochrone (0.07 dex), consistent with our error estimate (0.05 dex). However, the [Fe/H] trend is not reproducible. This shows that the data have the potential to reveal patterns of the magnitude of the expected physical effects, but the analysis methods need to be refined to cull systematic effects that currently dominate the patterns.
Document type :
Journal articles
Complete list of metadata

Contributor : Olivier Hauss Connect in order to contact the contributor
Submitted on : Sunday, February 28, 2021 - 12:09:07 PM
Last modification on : Wednesday, November 3, 2021 - 9:13:50 AM
Long-term archiving on: : Saturday, May 29, 2021 - 6:08:49 PM


Publisher files allowed on an open archive




Rashi Jain, Philippe Prugniel, Lucimara Martins, Ariane Lançon. NGC 6397: The metallicity trend along the isochrone revisited. Astronomy and Astrophysics - A&A, EDP Sciences, 2020, 635, pp.A161. ⟨10.1051/0004-6361/201936952⟩. ⟨hal-03151891⟩



Record views


Files downloads