A Catalog of 486 Barium Stars Identified in GALAH DR4

Abstract

We present a catalog of 486 Ba stars identified in the GALAH DR4 survey using high-resolution spectra and precise abundance measurements. The sample was selected based on s-process enrichment criteria involving the abundances of Ba and La relative to Eu, and further refined using the signed-distance method, resulting in the largest sample of Ba stars to date, including five newly identified Ba dwarfs. Using astrometric and kinematic parameters from Gaia DR3 and StarHorse, we derived the Galactic velocity components for 367 Ba stars and found that most belong to the thin or thick disk, while 18 exhibit halo-like kinematics. Chemical abundance analysis suggests that most Ba stars are of in situ origin, whereas two stars (4077588766331013248 and 6692980582560946304) display signatures of accreted populations. The E-Lz diagram further shows that star 4077588766331013248 lies within the region of substructure ED-8. The observed decline of [Ba/Fe] and [La/Fe] with increasing metallicity implies that s-process elements originate from nucleosynthetic sites distinct from those of iron-peak elements, while the decreasing [hs/ls] ratio toward higher metallicity indicates higher neutron capture efficiency at lower metallicity. Both giant and dwarf Ba stars-except for 6053735173729807872-are confirmed binaries hosting white dwarf companions. Moreover, we estimated the masses of the former asymptotic giant branch (AGB) companions to these Ba stars based on the good agreement between the FRUITY AGB model predictions and their observed abundance patterns.

Figures (14)

• Figure 1: Distribution of the $d_{\rm s}$ distances for the Ba stars in our sample. The corresponding mean ($\mu$) and standard deviation ($\sigma$) are indicated in the figure.
• Figure 2: Histograms of $T_{\rm eff}$, $\log g$, and [Fe/H] for the Ba star sample.
• Figure 3: Kiel diagram of Ba stars in GALAH, with points colored according to their metallicities. For reference, all GALAH DR4 stars are plotted in the background as filled gray circles.
• Figure 4: The Toomre diagram of $(U_{\rm LSR}^{2}+W_{\rm LSR}^{2})^{1/2}$ vs. $V_{\rm LSR}$ for our sample stars. Black- and red-filled circles represent Ba giants with near-solar metallicities ($-0.5 <$ [Fe/H] $< 0.64$) and subsolar metallicities ([Fe/H] $\le -0.5$), respectively. Green-filled circles denote the five newly identified Ba dwarfs in this work. The semicircular curves indicate the boundaries separating thin-disk, thick-disk, and halo populations, with $V_{\rm tot} = (U_{\rm LSR}^{2} + V_{\rm LSR}^{2} + W_{\rm LSR}^{2})^{1/2}$ less than 85 km s$^{-1}$ (blue curve) and 180 km s$^{-1}$ (red curve), respectively Chen2004.
• Figure 5: Spatial distribution of the 367 Ba stars, mostly located within 4 kpc, plotted as vertical height versus Galactocentric radius. Filled black and red circles represent Ba giants associated with the Galactic disk and halo, respectively. Filled green circles denote Ba dwarfs.