Behavior of Abundances in Chemically Peculiar Dwarf and Subgiant A-Type Stars: HD 23193 and HD 170920

Abstract

To understand the origin of the abundance peculiarities of non-magnetic A-type stars, we present the first detailed chemical abundance analysis of a metallic line star HD 23193 (A2m) and an A-type subgiant HD 170920 (A5) which could have been a HgMn star on the main sequence. Our analysis is based on medium (R$\sim$14000) and high (R$\sim$40000) resolution spectroscopic data of the stars. The abundance of 18 elements are derived: C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, Sr, Y, and Ba. The masses of HD 23193 and HD 170920 are estimated from evolutionary tracks, as $2.3\pm 0.1$ $M_{\odot }$ and $2.9\pm 0.1$ $M_{\odot }$. The ages are found $635\pm 33$ Myr for HD 23193 and $480\pm 50$ Myr for HD 170920 using isochrones. The abundance pattern of HD 23193 shows deviations from solar values in the iron-peak elements and indicates remarkable overabundances of Sr (1.16), Y (1.03), and Ba (1.24) with respect to the solar abundances. We compare the derived abundances of this moderately rotating ($v$sin$i=37.5$ km s${}^{-1}$) Am star to the theoretical chemical evolution models including rotational mixing. The theoretically predicted abundances resemble our derived abundance pattern, except for a few elements (Si and Cr). For HD 170920, we find nearly solar abundances, except for C ($-0.43$), S (0.16), Ti (0.15), Ni (0.16), Zn (0.41), Y (0.57), and Ba (0.97). Its low rotational velocity ($v$sin$i=14.5$ km s${}^{-1}$), reduced carbon abundance, and enhanced heavy element abundances suggest that the star is most-likely an evolved HgMn star.

arXiv commentAccepted for publication in The Astrophysical Journal, 7 pages, 4 tables, and 4 figures

References in corpus (11)

• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Validation of the new Hipparcos reduction
• On the use of empirical bolometric corrections for stars
• Pulkovo Compilation of Radial Velocities for 35495 Hipparcos Stars in a Common System
• Rotational velocities of A-type stars II. Measurement of vsini in the northern hemisphere
• A new catalogue of Stroemgren-Crawford uvbybeta photometry
• AmFm and lithium gap stars: Stellar evolution models with mass loss
• Carbon enrichment of the evolved stars in the Sagittarius dwarf spheroidal
• Can Sodium Abundances of A-Type Stars Be Reliably Determined from Na I 5890/5896 Lines?
• Chemical composition of intermediate mass stars members of the M6 (NGC 6405) open cluster
• Masses and age of the Chemically Peculiar double-lined binary $\chi$~Lupi

Cited by in corpus (1)

• Mass-effective temperature-surface gravity relation for intermediate-mass main-sequence stars