The s-process enriched star HD 55496: origin from a globular cluster or from the tidal disruption of a dwarf galaxy?

Abstract

We present a new abundance analysis of HD 55496, previously known as a metal-poor barium star. We found that HD 55496 has a metallicity [Fe/H] $=-1.55$ and is s-process enriched. We find that HD 55496 presents four chemical peculiarities: (i) a Na-O abundance anti-correlation; (ii) it is aluminum rich; (iii) it is carbon poor for a s-process enriched star and (iv) the heavy 2${}^{nd}$ s-process peak elements, such as Ba, La, Ce, and Nd, present smaller abundances than the lighter s-process elements, such as Sr, Y and Zr, which is not usually observed among the chemically-peculiar binary stars at this metallicity. The heavy-element abundance pattern suggests that the main source of the neutrons is the ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction. Taken all these abundance evidence together into consideration, this strongly suggests that HD 55496 is a "second generation of globular cluster star" formed from gas already strongly enriched in s-process elements and now is a field halo object. Our dynamical analysis, however, indicates that the past encounter probabilities with the known globular clusters is very small ($\le 6\%$). This evidence, together with the fact of having a retrograde motion, points to a halo intruder possibly originated from the tidal disruption of a dwarf galaxy.

References in corpus (15)

• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Pulkovo Compilation of Radial Velocities for 35495 Hipparcos Stars in a Common System
• Improved Laboratory Transition Probabilities for Neutral Chromium and Re-determination of the Chromium Abundance for the Sun and Three Stars
• Improved Laboratory Transition Probabilities for Ce II, Application to the Cerium Abundances of the Sun and Five r-process Rich, Metal-Poor Stars, and Rare Earth Lab Data
• CS 30322-023: an ultra metal-poor TP-AGB star?
• New analysis of the two carbon-rich stars CS 22948-27 and CS 29497-34 : binarity and neutron-capture elements
• CS22964-161: A Double-Lined Carbon- and s-Process-Enhanced Metal-Poor Binary Star
• Atypical Mg-poor Milky Way field stars with globular cluster second-generation like chemical patterns
• The completeness-corrected rate of stellar encounters with the Sun from the first Gaia data release
• Detailed Abundances of 15 Stars in the Metal-Poor Globular Cluster NGC 4833
• The Na-O anticorrelation in horizontal branch stars. V. NGC 6723
• Chemical analysis of CH stars - II: atmospheric parameters and elemental abundances
• A chemical signature from fast-rotating low-metallicity massive stars: ROA 276 in omega Centauri
• High-resolution spectroscopic observations of the new CEMP-s star CD-50${}^{\circ }$776

Cited by in corpus (2)

• Chemodynamics of newly identified giants with globular cluster like abundance patterns in the bulge, disk, and halo of the Milky Way
• On the Origin of Metal-poor Stars in the Solar Neighborhood