Discovery of an Extremely r-process-enhanced Thin-disk Star with [Eu/H] = +0.78

Abstract

Highly r-process-enhanced stars are rare and usually metal-poor ([Fe/H] < - 1.0), and mainly populate the Milky Way halo and dwarf galaxies. This study presents the discovery of a relatively bright (V = 12.72), highly r-process-enhanced (r-II) star ([Eu/Fe] = +1.32, [Ba/Eu] = - 0.95), LAMOST J020632.21 + 494127.9. This star was selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution (R ~ 7500) spectroscopic survey; follow-up high-resolution (R ~ 25,000) observations were conducted with the High Optical Resolution Spectrograph (HORuS) installed on the Gran Telescopio Canarias (GTC). The stellar parameters ($T_{\mathrm{eff}}$ = 4130 K, $\log \mathrm{g}$ = 1.52, $[Fe/H]$ = $-$0.54, $\xi$ = 1.80 $\mathrm{km}{\mathrm{s}}^{-1}$) have been inferred taking into account non-local thermodynamic equilibrium (NLTE) effects. The abundances of [Ce/Fe], [Pr/Fe], and [Nd/Fe] are +0.19, +0.65 and +0.64, respectively, relatively low compared to the Solar r-process pattern normalized to Eu. This star has a high metallicity ([Fe/H] = - 0.54) compared to most other highly r-process-enhanced stars, and has the highest measured abundance ratio of Eu to H ([Eu/H] = +0.78). It is classified as a thin-disk star based on its kinematics, and does not appear to belong to any known stream or dwarf galaxy.

5 figures, 3 tables

References in corpus (37)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• Origin of the heavy elements in binary neutron-star mergers from a gravitational wave event
• The mass distribution and gravitational potential of the Milky Way
• Spectroscopic identification of r-process nucleosynthesis in a double neutron star merger
• Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis
• Basic physical parameters of a selected sample of evolved stars
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Identification of strontium in the merger of two neutron stars
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• Neutron Star Mergers and Nucleosynthesis of Heavy Elements
• Carbon-Enhanced Metal-Poor Star Frequencies in the Galaxy: Corrections for the Effect of Evolutionary Status on Carbon Abundances
• CH in stellar atmospheres: an extensive linelist
• A non-LTE study of neutral and singly-ionized calcium in late-type stars
• Systematic non-LTE study of the $-2.6\le$ [Fe/H] $\le 0.2$ F and G dwarfs in the solar neighbourhood. II. Abundance patterns from Li to Eu
• The Gaia FGK Benchmark Stars - High resolution spectral library
• High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the SkyMapper Survey
• The origin and evolution of the odd-Z iron-peak elements Sc, V, Mn, and Co in the Milky Way stellar disk
• The $R$-Process Alliance: Fourth Data Release from the Search for $r$-Process-Enhanced Stars in the Galactic Halo
• Elemental abundances and classification of CEMP stars
• Overview of the LAMOST survey in the first decade
• The R-process Alliance: First Magellan/MIKE Release from the Southern Search for R-Process-enhanced Stars
• Nucleosynthesis in Magnetically Driven Jets from Collapsars
• Nine New Metal-Poor Stars on the Subgiant and Red Horizontal Branches with High Levels of r-process Enhancement
• RAVE J203843.2-002333: The first highly r-process-enhanced star identified in the RAVE survey
• NLTE study of scandium in the Sun
• Statistical equilibrium of silicon in the solar atmosphere
• GALExtin: An alternative online tool to determine the interstellar extinction in the Milky Way
• Abundances of disk and bulge giants from high-resolution optical spectra -- IV. Zr, La, Ce, Eu
• Evidence for the accretion origin of halo stars with an extreme r-process enhancement
• The R-Process Alliance: Abundance Universality among Some Elements at and between the First and Second R-Process Peaks
• The R-Process Alliance: J1521-3538, a very metal-poor, extremely r-process-enhanced star with [Eu/Fe]=+2.2, and the class of r-III stars
• Diversity of Abundance Patterns of Light Neutron-capture Elements in Very-metal-poor Stars
• Highly r-process enhanced stars in ultra-faint dwarf galaxies
• HORuS transmission spectroscopy of 55 Cnc e
• The R-Process Alliance: Discovery of a low-alpha, r-Process-Enhanced Metal-Poor Star in the Galactic Halo