Detalles de publicación
PP 026133
Stellar nucleosynthesis in the era of large surveys: S-process-polluted binaries in GALAH DR4
(1) IAC, (2) ULL ,(3) INAF-Torino, (4) IvS-KU Leuven, (5) VIU, (6) ULB, (7) University of Cambridge, (8) UDP
Context. Binary interactions during the asymptotic giant branch phase can lead to the formation of chemically peculiar stars such as Ba-, CH-, and CEMP-s stars with overabundances of s-process elements as well as carbon. Only a few hundred of these stars have been subject to detailed chemical and/or dynamical studies, typically in non-homogeneous samples.
Aims. We compile a systematic sample of s-process-polluted candidates using the fourth data release of the large spectroscopic survey GALAH. We also compare the chemical and orbital properties of these candidates with those of confirmed s-process-polluted stars to gain stronger evidence of their nature.
Methods. GALAH DR4 uses neural networks and automatic spectral analysis methods as well as data of a lower spectral resolution than is normally used to characterise these objects. We therefore built a validation sample of s-rich stars before querying the survey, for which we obtained VLT/UVES and Mercator/HERMES high-resolution (>80 000) spectra and analysed them with traditional methods. We compared our stellar parameters and individual abundances with those of the survey and used this validation to define the thresholds that a star in GALAH DR4 must pass to be flagged as a good s-process-rich candidate. Based on our comparisons with the high-resolution complementary spectra, we defined thresholds on five quantities: [s/Fe] > 0.40 dex, [Y/Fe] > 0.22 dex, [Zr/Fe] > 0.26 dex, [Ba/Fe] > 0.19 dex, and [La/Fe] > 0.26 dex.
Results. We identified 1059 stars in GALAH DR4 that are good candidates to be s-process-polluted stars, covering a broad parameter space (4000 K < Teff < 6000 K, 0.5 dex < log g < 5.0 dex, −2.0 dex < [Fe/H] < 0.5 dex). They share many similarities with the samples of confirmed s-rich stars, especially their ratios of heavy over light s-elements, which strengthens our confidence in the purity of the sample. When we cross-matched the sample with the literature, we found that only 7% of the candidates have measured orbital periods and eccentricities. This limits a full comparison with confirmed Ba and related star samples for now. However, their binary fraction is, as expected, higher than the one we found for the full GALAH DR4 catalogue.
Conclusions. Our sample of candidates is almost five times larger than the number of currently confirmed polluted stars. This and the fact that it has been homogeneously treated by the GALAH survey opens very interesting avenues to compare nucleosynthesis models as well as binary evolution models.
Aims. We compile a systematic sample of s-process-polluted candidates using the fourth data release of the large spectroscopic survey GALAH. We also compare the chemical and orbital properties of these candidates with those of confirmed s-process-polluted stars to gain stronger evidence of their nature.
Methods. GALAH DR4 uses neural networks and automatic spectral analysis methods as well as data of a lower spectral resolution than is normally used to characterise these objects. We therefore built a validation sample of s-rich stars before querying the survey, for which we obtained VLT/UVES and Mercator/HERMES high-resolution (>80 000) spectra and analysed them with traditional methods. We compared our stellar parameters and individual abundances with those of the survey and used this validation to define the thresholds that a star in GALAH DR4 must pass to be flagged as a good s-process-rich candidate. Based on our comparisons with the high-resolution complementary spectra, we defined thresholds on five quantities: [s/Fe] > 0.40 dex, [Y/Fe] > 0.22 dex, [Zr/Fe] > 0.26 dex, [Ba/Fe] > 0.19 dex, and [La/Fe] > 0.26 dex.
Results. We identified 1059 stars in GALAH DR4 that are good candidates to be s-process-polluted stars, covering a broad parameter space (4000 K < Teff < 6000 K, 0.5 dex < log g < 5.0 dex, −2.0 dex < [Fe/H] < 0.5 dex). They share many similarities with the samples of confirmed s-rich stars, especially their ratios of heavy over light s-elements, which strengthens our confidence in the purity of the sample. When we cross-matched the sample with the literature, we found that only 7% of the candidates have measured orbital periods and eccentricities. This limits a full comparison with confirmed Ba and related star samples for now. However, their binary fraction is, as expected, higher than the one we found for the full GALAH DR4 catalogue.
Conclusions. Our sample of candidates is almost five times larger than the number of currently confirmed polluted stars. This and the fact that it has been homogeneously treated by the GALAH survey opens very interesting avenues to compare nucleosynthesis models as well as binary evolution models.