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PENELLOPE: IX. Lithium, iron and barium elemental abundances in eight nearby young clusters

R. Carini, K. Biazzo, A. Frasca, C. F. Manara, J. M. Alcalá, P. Ábráham, J. Campbell-White, R. Claes, M. Fang, M. Gangi, J. F. Gameiro, Á. Kóspál, K. Mauco, I. Mendigutía, B. Nisini, M. Robberto, C. E. Robinson, C. Schneider, M. Siwak, T. Sperling, L. Tychoniec, L. Venuti

Abstract

We conducted a homogeneous chemical analysis of pre-main sequence stars with effective temperatures ranging from $\sim$ 3000 K to $\sim$ 5500 K in eight nearby star-forming regions (SFRs): Chamaeleon I, $η$ Chamaeleonis, Lupus, Orion OB1a, Orion OB1b, $σ$Orionis, Taurus, and Corona-Australis. Our study aims to: 1) derive the lithium abundance (A(Li)) and highlight the impact of veiling correction on both A(Li) and age determination; 2) perform the iron (Fe) and barium (Ba) abundance analysis in regions with scarce previous measurements; 3) investigate the possible Ba enhancement. The analyzed data were obtained as part of the PENELLOPE Large Program using the ESPRESSO, UVES, and X-Shooter instruments. We measured the equivalent width of the lithium line (EWLi) at $λ$ = 6707.8 Angstrom, from which A(Li) is derived using the curves of growth method. The Fe and Ba abundances have been measured through spectral synthesis analysis. Using the EAGLES code, we derived an upper limit on the age of the eight SFRs. Our findings underscore the necessity of veiling corrections on EWLi, which can shift A(Li) and age estimates by up to $\sim$ 0.7 dex and $\sim$ 20 Myr, respectively. Accounting for veiling, the A(Li) distributions peak in a range between 3.3 and 3.8 dex for most clusters, and the upper age limit is approximately 5 Myr for all SFRs. We successfully measured the mean iron and barium abundances in Lupus, Taurus, Cha I, and $η$ Cha, showing slightly sub-solar iron abundance, and a clear Ba overabundance, with [Ba/H] values reaching up to 0.75 dex.

PENELLOPE: IX. Lithium, iron and barium elemental abundances in eight nearby young clusters

Abstract

We conducted a homogeneous chemical analysis of pre-main sequence stars with effective temperatures ranging from 3000 K to 5500 K in eight nearby star-forming regions (SFRs): Chamaeleon I, Chamaeleonis, Lupus, Orion OB1a, Orion OB1b, Orionis, Taurus, and Corona-Australis. Our study aims to: 1) derive the lithium abundance (A(Li)) and highlight the impact of veiling correction on both A(Li) and age determination; 2) perform the iron (Fe) and barium (Ba) abundance analysis in regions with scarce previous measurements; 3) investigate the possible Ba enhancement. The analyzed data were obtained as part of the PENELLOPE Large Program using the ESPRESSO, UVES, and X-Shooter instruments. We measured the equivalent width of the lithium line (EWLi) at = 6707.8 Angstrom, from which A(Li) is derived using the curves of growth method. The Fe and Ba abundances have been measured through spectral synthesis analysis. Using the EAGLES code, we derived an upper limit on the age of the eight SFRs. Our findings underscore the necessity of veiling corrections on EWLi, which can shift A(Li) and age estimates by up to 0.7 dex and 20 Myr, respectively. Accounting for veiling, the A(Li) distributions peak in a range between 3.3 and 3.8 dex for most clusters, and the upper age limit is approximately 5 Myr for all SFRs. We successfully measured the mean iron and barium abundances in Lupus, Taurus, Cha I, and Cha, showing slightly sub-solar iron abundance, and a clear Ba overabundance, with [Ba/H] values reaching up to 0.75 dex.

Paper Structure

This paper contains 15 sections, 10 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Data
  3. Analysis of the lithium line
  4. Equivalent Width Determination
  5. Lithium variation
  6. Abundance of $^{7}\rm Li$
  7. Influence of veiling on age estimate based on Li diagnostics
  8. Iron and Barium abundance
  9. Error estimate
  10. Iron abundance in the context of nearby SFRs
  11. The barium abundance conundrum
  12. Conclusions
  13. Tables of effective temperature, veiling, Equivalent Widths, and Lithium Abundances values with fit errors.
  14. Microturbulence ($\xi$) and macroturbulence ($v_{mac}$) velocities for the subsample of targets selected for [Fe/H] and [Ba/H] abundance measurements.
  15. Upper age limit estimates

Figures (10)

  • Figure 1: Multi-panel overview of the lithium equivalent widths for the eight SFRs (Cha I, $\eta$ Cha, Lupus, Taurus, Orion OB1a, Orion OB1b, $\sigma$ Ori and CrA) in our sample. For each region, the left sub-panel shows lithium equivalent width versus $T_{\rm eff}$. The red squares represent the EW corrected for blending with the iron line ($EW_{\rm Li}^{\rm Fe}$), the black dots represent the equivalent width after further correction for spectral veiling ($EW_{\rm Li}^{\rm veil+Fe}$). K-type ( T $\geq$ 4000 K) and M-type (T < 4000 K) stars are denoted by filled and open symbols, respectively. Arrows indicate upper limits due to the unresolved contribution of the FeI $\lambda$6707.4 line. The empirical model isochrones by jef23 at 5, 10, 15, 20 Myr are over plotted. The right sub-panels display the corresponding $EW_{\rm Li}^{\rm veil+Fe}$ distribution.
  • Figure 2: ($EW_{\rm Li}^{veil}$-$EW_{\rm Li}^{\rm raw}$)/$EW_{\rm Li}^{\rm veil}$ as a function of $T_{\rm eff}$. The filled black dots and the filled red triangles represent high (ESPRESSO + UVES) and medium (X-Shooter) resolution data, respectively.
  • Figure 3: Variation of $EW_{\rm Li}^{\rm raw}$ across the observing epochs as a function of $T_{\rm eff}$ variations, for ESPRESSO and UVES data. The blue dotted lines represent 3 $\sigma$ values.
  • Figure 4: Variation of $EW_{\rm Li}^{\rm veil+Fe}$ across the observing epochs as a function of veiling variations, for ESPRESSO and UVES data.The blue dotted lines represent 3 $\sigma$ values
  • Figure 5: Multi-panel overview of the lithium abundance for the eight SFRs (Cha I, $\eta$ Cha, Lupus, Taurus, Orion OB1a, Orion OB1b, $\sigma$ Ori and CrA). For each region, the left sub-panel shows NLTE-corrected lithium abundance as a function of effective temperature. Red squares and black dots represent the $A{\rm (Li)}$ values derived from $EW_{\rm Li}^{\rm Fe}$ and $EW_{\rm Li}^{\rm veil+Fe}$, respectively. K-type and M-type stars are plotted with filled and open symbols, respectively. The lithium isochrones by baraffe15 in the 2-20 Myr range are overlaid with dot-dashed lines. Arrows refer to lower (stars whose final $A{\rm (Li)}$ value exceeds 4.0 dex, see text) or upper (due to the unresolved contribution of the FeI $\lambda$ 6707.4 line) limits. Each right sub-panel displays the histogram of the corresponding $A{\rm (Li)}$ (corrected for veiling) distribution.
  • ...and 5 more figures