Rubidium abundances in solar metallicity stars

Abstract

A Rb deficiency by a factor two with respect to the Sun has been found in M dwarfs of solar metallicity. This deficiency is difficult to understand from both the observational and nucleosynthesis point of views. To test the reliability of this Rb deficiency, we study the Rb and Zr abundances in a sample of KM-type giant stars in a similar metallicity range extracted from the AMBRE Project. We derive Rb and Zr abundances in 54 giant stars with metallicity close to solar by spectral synthesis in LTE and NLTE. The impact of the Zeeman broadening in the RbI line is also studied. The LTE analysis results in a Rb deficiency in giant stars smaller than that obtained in M dwarfs, but the NLTE [Rb/Fe] ratios are very close to solar in the full metallicity range. This contrasts with the figure found in M dwarfs. We investigate the effect of gravitational settling and magnetic activity as possible causes of the Rb deficiency found in M dwarfs. While, the former phenomenon has a negligible impact on the surface Rb abundance, the existence of an average magnetic field with intensity typical of that observed in M dwarfs may result in systematic Rb abundance underestimations if the Zeeman broadening is not considered in the spectral synthesis. The new [Rb,Zr/Fe] vs. [Fe/H] relationships can be explained when the Rb production by rotating massive stars and low-and-intermediate mass stars are considered, without the need of any deviation from the standard s-process nucleosynthesis in AGB stars as previously suggested.

arXiv comment21 pages, 4 figures, accepted in Astronomy & Astrophysics

References in corpus (67)

• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
• The GALAH Survey: Scientific Motivation
• The s Process: Nuclear Physics, Stellar Models, Observations
• Origin of the Heaviest Elements: the Rapid Neutron-Capture Process
• Presupernova evolution and explosive nucleosynthesis of rotating massive stars in the metallicity range -3 <=[Fe/H]<= 0
• New PARSEC evolutionary tracks of massive stars at low metallicity: testing canonical stellar evolution in nearby star forming dwarf galaxies
• Chemodynamical evolution of the Milky Way disk I: The solar vicinity
• Evolution, nucleosynthesis and yields of low mass AGB stars
• The RAdial Velocity Experiment (RAVE): Fourth data release
• The GALAH Survey: Second Data Release
• Neutron Star Mergers and Nucleosynthesis of Heavy Elements
• Chemical evolution with rotating massive star yields: I. The solar neighbourhood and the s-process elements
• Evolution, nucleosynthesis and yields of AGB stars at different metallicities (III): intermediate mass models, revised low mass models and the ph-FRUITY interface
• Gaia FGK Benchmark Stars: Effective temperatures and surface gravities
• Fundamental parameters and infrared excesses of Hipparcos stars
• The CARMENES search for exoplanets around M dwarfs: High-resolution optical and near-infrared spectroscopy of 324 survey stars
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program II: Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd and Eu
• The elemental composition of the Sun III. The heavy elements Cu to Th
• Chemical similarities between Galactic bulge and local thick disk red giant stars
• The CARMENES search for exoplanets around M dwarfs: Different roads to radii and masses of the target stars
• Age dissection of the Milky Way discs: red giants in the Kepler field
• Atomic data for the Gaia-ESO Survey
• Accuracy and precision of industrial stellar abundances
• Evolution of the Milky Way with radial motions of stars and gas I. The solar neighborhood and the thin and thick disk
• The Kr85 s-process Branching and the Mass of Carbon Stars
• Automated derivation of stellar atmospheric parameters and chemical abundances: the MATISSE algorithm
• The origin and evolution of r- and s-process elements in the Milky Way stellar disk
• Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components
• Rubidium-Rich Asymptotic Giant Branch Stars
• The AMBRE project: A new synthetic grid of high-resolution FGKM stellar spectra
• Magnetic fields of M dwarfs
• Atomic and Molecular Data for Optical Stellar Spectroscopy
• The Magnetic Fields at the Surface of Active Single G-K Giants
• The CARMENES search for exoplanets around M dwarfs - Photospheric parameters of target stars from high-resolution spectroscopy
• Stellar population models in the UV: I. Characterisation of the New Generation Stellar Library
• Magnetic fields in M dwarfs from the CARMENES survey
• New insights on Ba over-abundance in open clusters. Evidence for the intermediate neutron-capture process at play?
• News on the s process from young open clusters
• Rubidium in Metal-Deficient Disk and Halo Stars
• Is Extra Mixing Really Needed in Asymptotic Giant Branch Stars?
• Temperatures and Metallicities of M dwarfs in the APOGEE Survey
• Abundances in the Local Region I: G and K Giants
• The importance of the 13C(alpha,n)16O reaction in Asymptotic Giant Branch stars
• The Gaia-ESO Survey: the origin and evolution of s-process elements
• Stellar Characterization of M-dwarfs from the APOGEE Survey: A Calibrator Sample for the M-dwarf Metallicities
• Rubidium and lead abundances in giant stars of the globular clusters M 13 and NGC 6752
• Abundances in bulge stars from high-resolution, near-IR spectra I. The CNO elements observed during the science verification of CRIRES at VLT
• The Gaia-ESO Survey: Empirical determination of the precision of stellar radial velocities and projected rotation velocities
• A Method to Derive the Absolute Composition of the Sun, the Solar System and the Stars
• Abundances of disk and bulge giants from high-resolution optical spectra -- IV. Zr, La, Ce, Eu
• Solar twins and the Barium puzzle
• The AMBRE Project: Stellar Parameterisation of the ESO:UVES archived spectra
• Formation of Zr I and II lines under non-LTE conditions of stellar atmospheres
• A near-IR line of Mn I as a diagnostic tool of the average magnetic energy in the solar photosphere
• Determination of the spectroscopic stellar parameters for 257 field giant stars
• The CARMENES search for exoplanets around M dwarfs: Rubidium abundances in nearby cool stars
• Abundances and Depletions of Neutron-Capture Elements in the Interstellar Medium
• Enrichment of the Galactic disc with neutron capture elements: Sr
• Abundances of disk and bulge giants from hi-res optical spectra: I. O, Mg, Ca, and Ti in the Solar neighborhood and Kepler field samples
• Wilson-Bappu Effect: Extended to Surface Gravity
• Rubidium in the Interstellar Medium
• Experimental isotope shifts of the 5 ${}^2{S}_{1/2}$ state and low-lying excited states of Rb

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