High-resolution abundance analysis of HD 140283

Abstract

Context. HD 140283 is a reference subgiant that is metal poor and confirmed to be a very old star. The element abundances of this type of old star can constrain the nature and nucleosynthesis processes that occurred in its (even older) progenitors. The present study may shed light on nucleosynthesis processes yielding heavy elements early in the Galaxy. Aims. A detailed analysis of a high-quality spectrum is carried out, with the intent of providing a reference on stellar lines and abundances of a very old, metal-poor subgiant. We aim to derive abundances from most available and measurable spectral lines. Methods. The analysis is carried out using high-resolution (R = 81 000) and high signal-to-noise ratio (800 < S /N/pixel < 3400) spectrum, in the wavelength range 3700 < λ(Å) < 10475, obtained with a seven-hour exposure time, using the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) at the Canada-France-Hawaii Telescope (CFHT). The calculations in local thermodynamic equilibrium (LTE) were performed with a OSMARCS 1D atmospheric model and the spectrum synthesis code Turbospectrum, while the analysis in non-LTE (NLTE) is based on the MULTI code. We present LTE abundances for 26 elements, and NLTE calculations for the species C i, O i, Na i, Mg i, Al i, K i, Ca i, Sr ii, and Ba ii lines.Results. The abundance analysis provided an extensive line list suitable for metal-poor subgiant stars. The results for Li, CNO, α-, and iron peak elements are in good agreement with literature. The newly NLTE Ba abundance, along with a NLTE Eu correction and a 3D Ba correction from literature, leads to [Eu/Ba] = +0.59 ± 0.18. This result confirms a dominant r-process contribution, possibly together with a very small contribution from the main s-process, to the neutron-capture elements in HD 140283. Overabundances of the lighter heavy elements and the high abundances derived for Ba, La, and Ce favour the operation of the weak r-process in HD 140283.

Abundance patterns of the light neutron-capture elements in very and extremely metal-poor stars

“…It has been shown (but often overlooked) that, in the old stars, there is an excellent correlation between the two ratios [Eu/Fe] and [Ba/Fe]. In Fig.4A [Eu/Ba] is plotted versus [Ba/Fe] for the stars studied from the LP First Stars and the stars studied in a similar way by Siqueira Mello et al (2014) and Siqueira- Mello et al (2015). In these very old stars, we found [Eu/Ba] = 0.51 ± 0.09 dex.…”

KIC 9821622: An interesting lithium-rich giant in theKeplerfield

“…For the abundance obtained from the IR triplet we applied the empirical NLTE corrections by Afşar et al (2012). Carbon was derived by fitting the features at 8335 and 9061.43 Å (Siqueira-Mello et al 2015), while the nitrogen abundance was determined based on CN bands near 8300 Å. The 12 C/ 13 C ratio was derived by synthesizing the λ8002-8004.65 Å region.…”

Iterative precision measurement of branching ratios applied to 5Pstates in88Sr+

“…Despite their relevance, branching ratios of heavy atoms have not been precisely measured for many decades due to the large uncertainties inherent in traditional discharge chamber methods using the Hanle effect [18]. Recent astrophysical studies still use these older experimental results for fitting emission spectra [12,13]. Only in the last decade have there been measurements of branching ratios at the 1% level [19][20][21][22] using trapped ions, which are versatile toolkits for precision spectroscopy [4,15,23] as well as quantum computation [24].…”

“…Branching ratios for different atomic species are also of great use in a wide range of fields including astrophysics, where analyzing the composition of stars contributes greatly to understanding stellar formation and evolution. Abundances of heavy elements such as strontium are essential for determining the efficiency of neutron capture processes in metal-poor stars, yet can be difficult to determine from emission spectra due to nearby transitions of other elements [7][8][9][10][11][12][13]. Branching ratios of these transitions are therefore vital for quantitative modeling of nucleosynthesis processes [11][12][13].…”