Silicon and Strontium abundances of very metal-poor stars determined from near-infrared spectra

Abstract

Silicon and Strontium are key elements to explore the nucleosynthesis and chemical evolution of the Galaxy by measurements of very metal-poor stars. There are, however, only a few useful spectral lines of these elements in the optical range that are measurable for such low-metallicity stars. Here we report on abundances of these two elements determined from near-infrared high-resolution spectra obtained with the Subaru Telescope Infrared Doppler instrument (IRD). Si abundances are determined for as many as 26 Si lines for six very and extremely metal-poor stars (-4.0<[Fe/H]<-1.5), which significantly improves the reliability of the abundance measurements. All six stars, including three carbon-enhanced objects, show over-abundances of Si ([Si/Fe]~+0.5). Two stars with [Fe/H]~-1.5 have relatively small over-abundances. The [Mg/Si] ratios agree with the solar value, except for one metal-poor star with carbon excess. Strontium abundances are determined from the triplet lines for four stars, including two for the first time. The consistency of the Sr abundances determined from near-infrared and optical spectra require further examination from additional observations.

arXiv comment3 figures, 6 tables, PASJ, in press

References in corpus (28)

• The chemical composition of the Sun
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• The s Process: Nuclear Physics, Stellar Models, Observations
• Origin of the Heaviest Elements: the Rapid Neutron-Capture Process
• Nucleosynthesis and Evolution of Massive Metal-Free Stars
• Galactic Evolution of Sr, Y, Zr: A Multiplicity of Nucleosynthetic Processes
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• Spectroscopic Studies of Extremly Metal-Poor Stars with Subaru/HDS:II.The r-process Elements, Including Thorium
• The Most Metal-Poor Stars. II. Chemical Abundances of 190 Metal-Poor Stars Including 10 New Stars With [Fe/H] < -3.5
• Extremely Metal-Poor Stars. VIII. High-Resolution, High-Signal-To-Noise Analysis of Five Stars with [Fe/H] < -3.5
• Near-UV Observations of HD221170: New Insights into the Nature of r-Process-Rich Stars
• Current Status of r-Process Nucleosynthesis
• The elemental composition of the Sun III. The heavy elements Cu to Th
• Spectroscopic Studies of Very Metal-Poor Stars with the Subaru High Dispersion Spectrograph. III. Light Neutron-Capture Elements
• Abundances in the Local Region II: F, G and K Dwarfs and Subgiants
• The Initial mass function of the first stars inferred from extremely metal-poor stars
• High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the SkyMapper Survey
• r-Process Calculations and Galactic Chemical Evolution
• More lead stars
• BD +44 493: A Ninth Magnitude Messenger from the Early Universe; Carbon Enhanced and Beryllium Poor
• Are There Any Stars Lacking Neutron-Capture Elements? Evidence from Strontium and Barium
• Chemical Analysis of the Ninth Magnitude Carbon-Enhanced Metal-Poor Star BD+44 493
• Precision radial velocity measurements by the forward-modeling technique in the near-infrared
• Spectroscopic Studies of Extremely Metal-Poor Stars with Subaru/HDS:I. Observational Data
• Hubble Space Telescope Near-Ultraviolet Spectroscopy of Bright CEMP-s Stars
• LAMOST J2217+2104: a new member of carbon-enhanced extremely metal-poor stars with excesses of Mg and Si
• Chemical abundance analysis of extremely metal-poor stars in the Sextans dwarf spheroidal galaxy
• Probing 3D and NLTE models using APOGEE observations of globular cluster stars