Spectroscopic study of CEMP-(s & r/s) stars- Revisiting classification criteria and formation scenarios, highlighting i-process nucleosynthesis

Abstract

We have derived the stellar atmospheric parameters, the effective temperature T${}_{eff}$, the microturbulent velocity $\zeta$, the surface gravity log g, and the metallicity [Fe/H] for HE 0017+0055, HE 2144-1832, HE 2339-0837, HD 145777, and CD-27 14351 from local thermodynamic equilibrium analyses using model atmospheres. Elemental abundances of C, N, $\alpha$-elements, iron-peak elements, and several neutron-capture elements are estimated using the equivalent width measurement technique as well as spectrum synthesis calculations in some cases. In the context of the double enhancement observed in four of the programme stars, we have critically examined whether the literature i-process model yields ([X/Fe]) of heavy elements can explain the observed abundance distribution. The estimated metallicity [Fe/H] of the programme stars ranges from -1.63 to -2.74. All five stars show enhanced abundance for Ba, and four of them exhibit enhanced abundance for Eu. Based on our analysis, HE 0017+0055, HE 2144-1832, and HE 2339-0837 are found to be CEMP-r/s stars, whereas HD 145777 and CD-27 14351 show characteristic properties of CEMP-s stars. From a detailed analysis of different classifiers of CEMP stars, using a large sample of similar stars from the literature, we have identified the one which best describes the CEMP-s and CEMP-r/s stars. We have also examined if [hs/ls] alone can be used as a classifier, and if there are any limiting values for [hs/ls] ratio that can be used to distinguish CEMP-s and CEMP-r/s stars. In spite of peaking at different values of [hs/ls], CEMP-s and CEMP-r/s stars show an overlap in the range 0.0 < [hs/ls] < 1.5 and hence this ratio alone can not be used to distinguish CEMP-s and CEMP-r/s stars.

arXiv comment27 pages, 16 figures, accepted for publication in Astronomy & Astrophysics (A&A)

References in corpus (105)

• The chemical composition of the Sun
• Local Kinematics and the Local Standard of Rest
• X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope
• Neutron capture in low mass Asymptotic Giant Branch stars: cross sections and abundance signatures
• Elemental Abundance Survey of The Galactic Thick Disk
• Nucleosynthesis in neutrino-driven winds: I. The physical conditions
• Neutron-Capture Elements in the Early Galaxy: Insights from a Large Sample of Metal-Poor Giants
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• The Hamburg/ESO R-process Enhanced Star survey (HERES) II. Spectroscopic analysis of the survey sample
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• Gaia Data Release 2: Mapping the Milky Way disc kinematics
• Fundamental parameters and infrared excesses of Hipparcos stars
• Super and massive AGB stars - IV. Final fates - Initial to final mass relation
• The s process in asymptotic giant branch stars of low metallicity and the composition of carbon-enhanced metal-poor stars
• Abundances of 30 elements in 23 metal-poor stars
• The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models
• Convective-reactive proton-C12 combustion in Sakurai's object (V4334 Sagittarii) and implications for the evolution and yields from the first generations of stars
• A holistic approach to carbon-enhanced metal-poor stars
• Oxygen trends in the Galactic thin and thick disks
• A Subaru/HDS study of Lead (Pb) abundances in eight s-process-element-rich, metal-poor stars
• The intermediate neutron-capture process and carbon-enhanced metal-poor stars
• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• On the correlation of elemental abundances with kinematics among galactic disk stars
• TOPoS: II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies
• Binarity in Carbon-Enhanced Metal-Poor stars
• From Nuclei to the Cosmos: Tracing Heavy-Element Production with the Oldest Stars
• Line lists for the A2PI-X2Sigma+ (red) and {B2Sigma+-X2Sigma} (violet) Systems of CN, 13C14N, and 12C15N, and Application to Astronomical Spectra
• Evolution and nucleosynthesis of asymptotic giant branch stellar models of low metallicity
• Wind Roche-lobe overflow: Application to carbon-enhanced metal-poor stars
• Carbon-enhanced Metal-poor Stars in SDSS/SEGUE. I. Carbon Abundance Estimation and Frequency of CEMP Stars
• The role of binaries in the enrichment of the early Galactic halo. III. Carbon-enhanced metal-poor stars -- CEMP-s stars
• The Hamburg/ESO R-process Enhanced Star survey (HERES) III. HE 0338-3945 and the formation of the r+s stars
• Evolution and Nucleosynthesis of Extremely Metal Poor & Metal-Free Low- and Intermediate-Mass Stars I: Stellar Yield Tables and the CEMPs
• Line strengths and updated molecular constants for the C2 Swan system
• Neutron Capture Elements in s-Process-Rich, Very Metal-Poor Stars
• The stellar content of the Hamburg/ESO survey. II. A large, homogeneously-selected sample of high latitude carbon stars
• Carbon-Enhanced Metal-Poor Stars. III. Main-Sequence Turn-Off Stars from the SDSS/SEGUE Sample
• Abundance Analysis of HE2148-1247, A Star With Extremely Enhanced Neutron Capture Elements
• Stellar Archaeology: a Keck Pilot Program on Extremely Metal- Poor Stars From the Hamburg/ESO Survey. III. The Lead (Pb) Star HE 0024-2523
• s-Process in Low Metallicity Stars. III. Individual analysis of CEMP-s and CEMP-s/r with AGB models
• Carbon Stars in the Hamburg/ESO Survey: Abundances
• More lead stars
• On the Perils of Hyperfine Splitting: A reanalysis of Mn and Sc Abundance Trends
• First stars IV.CS 29497-030: Evidence for operation of the s-process at very low metallicity
• i-process nucleosynthesis and mass retention efficiency in He-shell flash evolution of rapidly accreting white dwarfs
• Evolution of the Barium abundance in the early Galaxy from a NLTE analysis of the Ba lines in a homogeneous sample of EMP stars
• Binary properties of CH and Carbon-Enhanced Metal-Poor stars
• H ingestion into He-burning convection zones in super-AGB stellar models as a potential site for intermediate neutron-density nucleosynthesis
• Three carbon-enhanced metal-poor dwarf stars from the SDSS - Chemical abundances from CO^5BOLD 3D hydrodynamical model atmospheres
• New analysis of the two carbon-rich stars CS 22948-27 and CS 29497-34 : binarity and neutron-capture elements
• Near-UV Observations of CS29497-030: New Constraints on Neutron-Capture Nucleosynthesis Processes
• An Extremely Carbon-rich, Extremely Metal-poor Star in the Segue 1 System
• The Diverse Origins of Neutron-Capture Elements in the Metal-Poor Star HD 94028: Possible Detection of Products of i-process Nucleosynthesis
• Elemental abundances and classification of CEMP stars
• 3D hydrodynamical simulations of a proton ingestion episode in a low-metallicity asymptotic giant branch star
• Stellar Sources for Heavy r-Process Nuclei
• Pop III $\text{i}$-process Nucleosynthesis and the Elemental Abundances of SMSS J0313-6708 and the Most Iron-Poor Stars
• A high-resolution spectral analysis of three carbon-enhanced metal-poor stars
• The i-process yields of rapidly-accreting white dwarfs from multicycle He-shell flash stellar evolution models with mixing parameterizations from 3D hydrodynamics simulations
• 3D NLTE analysis of the most iron-deficient star, SMSS0313-6708
• Observational evidence for a different IMF in the early Galaxy
• NLTE strontium abundance in a sample of extremely metal poor stars and the Sr/Ba ratio in the early Galaxy
• The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal
• Asymptotic Giant Branch models at very low metallicity
• Chemical abundances in 43 metal-poor stars
• The s-process in metal-poor stars: Abundances for 22 neutron-capture elements in CS 31062-050
• Low-mass supernovae in the early Galactic halo: source of the double r/s-process enriched halo stars?
• Evolution and nucleosynthesis of extremely metal-poor and metal-free low- and intermediate-mass stars II. s-process nucleosynthesis during the core He flash
• Metal-Poor Stars Observed with the Magellan Telescope I. Constraints on Progenitor Mass and Metallicity of AGB Stars Undergoing s-Process Nucleosynthesis
• Carbon-enhanced metal-poor stars: a window on AGB nucleosynthesis and binary evolution. I. Detailed analysis of 15 binary stars with known orbital periods
• New Neutron-Capture Site in Massive Pop III and Pop II Stars as a Source for Heavy Elements in the Early Galaxy
• Granulation properties of giants, dwarfs, and white dwarfs from the CIFIST 3D model atmosphere grid
• Ba & Eu Abundances in M15 giant stars
• Abundances and kinematics of carbon-enhanced metal-poor stars in the Galactic halo*; A new classification scheme based on Sr and Ba
• Learning about the intermediate neutron-capture process from lead abundances
• A NLTE line formation for neutral and singly-ionised titanium in model atmospheres of the reference A-K stars
• Abundances of carbon-enhanced metal-poor stars as constraints on their formation
• CH stars at High Galactic Latitudes
• How plausible are the proposed formation scenarios of CEMP-r/s stars?
• The 13C-Pocket Structure in AGB Models: Constraints from Zirconium Isotope Abundances in Single Mainstream SiC Grains
• i-Process Contribution of Rapidly Accreting White Dwarfs to the Solar Composition of First-Peak Neutron-Capture Elements
• Ultra metal-poor stars: Spectroscopic determination of stellar atmospheric parameters using iron Non-LTE line abundances
• Chemical Abundances of the Outer Halo Stars in the Milky Way
• Post-AGB stars in the Magellanic Clouds and neutron-capture processes in AGB stars
• The R-Process Alliance: Discovery of the first metal-poor star with a combined r- and s-process element signature
• Enrichment of Very Metal-Poor Stars with Both r-Process and s-Process Elements from 8-10 M_\odot Stars
• An in-depth spectroscopic examination of molecular bands from 3D hydrodynamical model atmospheres I. Formation of the G-band in metal-poor dwarf stars
• Tool for Automatic Measurement of Equivalent width (TAME)
• The CH fraction of Carbon stars at high Galactic latitudes
• The first stars: a classification of CEMP-no stars
• Chemical analysis of CH stars - I: atmospheric parameters and elemental abundances
• [O/Fe] Estimates for Carbon-Enhanced Metal-Poor Stars from Near-IR Spectroscopy
• Chemical Compositions of Kinematically Selected Outer Halo Stars
• Chemical analysis of CH stars - III: Atmospheric parameters and elemental abundances
• An Explosive End to Intermediate-Mass Zero-Metallicity Stars and Early Universe Nucleosynthesis
• Subaru/HDS study of CH stars: elemental abundances for stellar neutron-capture process studies
• Identification of a Group III CEMP-no Star in the Dwarf Spheroidal Galaxy Canes Venatici I
• Neutron-capture elements in dwarf galaxies II: Challenges for the s- and i-processes at low metallicity
• Characterizing the companion AGBs using surface chemical composition of barium stars
• Radiative levitation in carbon-enhanced metal-poor stars with s-process enrichment
• HE 0017+0055 : A probable pulsating CEMP-rs star and long-period binary
• Abundances of neutron-capture elements in G 24-25. A halo-population CH subgiant
• A wide angle view of the Sagittarius dwarf spheroidal galaxy -- II. A CEMP-r/s star in the Sagittarius dwarf Spheroidal Galaxy
• Chemical analysis of a carbon-enhanced very metal-poor star: CD-27 14351

Cited by in corpus (23)

• Tracing Pop III supernovae with extreme energies through the Sculptor dwarf spheroidal galaxy
• Galactic chemical evolution of exoplanet host stars: Are high-mass planetary systems young?
• The Pristine survey -- XV. A CFHT ESPaDOnS view on the Milky Way halo and disc populations
• NLTE analysis of the methylidyne radical (CH) molecular lines in metal-poor stellar atmospheres
• Evidence for multiple nucleosynthetic processes from carbon enhanced metal-poor stars in the Carina dwarf spheroidal galaxy
• The Pristine Inner Galaxy Survey (PIGS) VII: a discovery of the first inner Galaxy CEMP-r/s star
• The Gaia-ESO survey: placing constraints on the origin of r-process elements
• Chemical analysis of two extremely metal-poor stars HE 2148-2039 and HE 2155-2043
• The peculiar abundances of HE 1005-1439. A carbon-enhanced extremely metal-poor star contaminated with products of both s-and i-process nucleosynthesis
• Spectroscopic study of four metal-poor carbon stars from the Hamburg/ESO Survey: On confirming the low-mass nature of their companions
• Chemodynamical study of two CEMP-no stars from the Hamburg/ESO Survey
• Metal-Poor Stars Observed with the Southern African Large Telescope II. An Extended Sample
• Closing the stellar labels gap: Stellar label independent evidence for [$\alpha /M$] information in Gaia BP/RP spectra
• Spectroscopic study of Ba and CEMP-s stars: Mass distribution of AGB progenitors
• High-resolution spectroscopic analysis of four new chemically peculiar stars
• Probing the nucleosynthetic contribution of low-metallicity, low-mass star companions of CEMP stars
• Discovery of a pair of very metal-poor stars enriched in neutron-capture elements: The proto-disk r-II star BPS CS 29529-0089 and the Gaia-Sausage-Enceladus r-I star TYC 9219-2422-1
• Modeling the progenitors of low-mass post-accretion binaries
• Distinct barium isotope ratios in CEMP-s and CEMP-rs stars
• LAMOST J045019.27+394758.7, with peculiar abundances of N, Na, V, Zn, is possibly a Sculptor dwarf galaxy escapee
• Ba Isotope Ratio in CEMP-s and CEMP-rs Stars as a Signature of s-Process and i-Process
• J-PLUS: Identifying Outlier Spectral Energy Distributions in the Fourth Data Release Using Unsupervised Machine Learning
• Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. IV. Heavy Element Enhanced Stars