BD+30${}^{\circ }$549: young helium-weak silicon star in NGC 1333 star-forming region

Abstract

We present results of the spectroscopic study of the chemically peculiar star BD+30${}^{\circ }$549 which is bona-fide member of young NGC 1333 star forming region. We found that the star possesses negligible rotation and helium-weak spectroscopic pattern with strongly enhanced Si II and Si III lines. The fundamental parameters of the star $T_{eff}$=13100~K and $\log (L/L_{\odot })$=2.1 indicate its age of about 2.7 Myr and position on the Hertzsprung-Russell diagram at the end of the Pre-Main Sequence evolutionary track, close to the Zero Age Main Sequence. Abundance analysis reveals the modest deficit of almost all elements with exception of Si, Fe, Ca and P which are overabundant. We performed the non-LTE calculations for Si II/Si III, Mg II and Ca II in order to check the influence of departures from LTE on line formation. Non-LTE calculations lead to much better reproduction of individual silicon line profiles, but does not completely remove the abundance discrepancy between Si II and Si III lines. We also investigate the effects of possible chemical stratification in BD+30${}^{\circ }$549. We suspect that the "Si II/Si III anomaly", observed in BD+30${}^{\circ }$549 spectrum arises under the combined action of the vertical and horizontal abundance gradients and non-LTE effects. We suppose that evolutionary status and phenomena observed in BD+30${}^{\circ }$549 indicate that conditions favorable for the selective diffusion and formation of the surface chemical composition peculiarities (slow rotation and stabilization of the atmosphere) can be built up already at the Pre-Main Sequence phase.

References in corpus (20)

• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-Ultraviolet Extinction and Its R-Dependence
• The elemental composition of the Sun II. The iron group elements Sc to Ni
• The elemental composition of the Sun I. The intermediate mass elements Na to Ca
• A non-LTE study of neutral and singly-ionized calcium in late-type stars
• Evolutionary state of magnetic chemically peculiar stars
• IN-SYNC II: Virial Stars from Sub-Virial Cores -- The Velocity Dispersion of Embedded Pre-Main-Sequence Stars in NGC 1333
• A cavity and further radial substructures in the disk around HD~97048
• Fe I Oscillator Strengths for Transitions from High-lying Even-Parity Levels
• Hyperfine Splitting in the VALD Database of Spectral-line Parameters
• Chemical stratification in the atmosphere of Ap star HD 133792. Regularized solution of the vertical inversion problem
• Theoretical analysis of the atmospheres of CP stars. Effects of the individual abundance patterns
• A 80 au cavity in the disk around HD 34282
• Statistical analysis of roAp, He-weak and He-rich stars
• A Star-sized Impact-Produced Dust Clump in the Terrestrial Zone of the HD 166191 System
• Survey of very broad Diffuse Interstellar Bands
• Putting atomic diffusion theory of magnetic ApBp stars to the test: evaluation of the predictions of time-dependent diffusion models
• A probable pre-main sequence chemically peculiar star in the open cluster Stock 16
• The chemical composition of the Herbig Ae SB2 system AK Sco (HD152404)
• Échelle Spectroscopy of the Chemically Peculiar Star ${\theta }^1$ Ori F