SCIENCE CHINA Physics, Mechanics & Astronomy
. Article . June 2014 Vol.57 No. 6: 1201–1205 doi: 10.1007/s11433-014-5475-4
Investigating the abundance enrichment pattern of heavy elements in the only observed CEMP-r/s star J004441.04-732136.4 of the SMC† CUI WenYuan1,2*, ZHANG Bo2 &ZHAOGang1,3
1School of Space Science and Physics, Shandong University at Weihai, Weihai 264209, China; 2College of Physics Science and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China; 3National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
Received March 19, 2014; accepted March 31, 2014; published online April 15, 2014
The post-AGB star J004441 is the first and the only one CEMP-r/s star found in SMC. Herein, we investigate the observed abun- dance pattern of the heavy elements using our parametric model. A consistent fitting results was obtained for the sample star. Based on the low r = 0.08, the s-process nucleosynthesis occurred in the interior is supposed to belong to the single neutron-exposure τ = . T9 1/2 −1 ffi event. The median value of 0 0 44( 0.348 ) mbarn supports a higher e ciency of the s-process nucleosynthesis relative to J004441 than that of the solar system, however, the value is not sufficiently high to favor the formation of a lead star. Thus, J004441 does not belong to lead star group. The large Cs value of J004441 supports the intrinsic characteristic of the s-enrichment. The Cr value is similar with that found in halo CEMP-r/s stars, which indicates that the r-process contributions is critical during heavy element enrichment. This star has a metallicity of [Fe/H] = −1.34, which is larger than that of Galaxy halo CEMP-r/sstars.The reason may be because of the different history of metallicity enrichment between the SMC and the Galaxy halo.
stellar nucleosynthesis, abundances, chemically peculiar stars
PACS number(s): 26.20.+f, 97.10.Cv, 97.10.Tk, 97.30.Fi
Citation: Cui W Y, Zhang B, Zhao G. Investigating the abundance enrichment pattern of heavy elements in the only observed CEMP-r/s star J004441.04-732136.4 of the SMC. Sci China-Phys Mech Astron, 2014, 57: 1201–1205, doi: 10.1007/s11433-014-5475-4
1 Introduction [1]. The site for the r-process, however, is unclear. Although there are many suggestions such as accretion-induced col- lapse [2], the mergers of neutron stars [3], and Type 1.5 su- Neutron-capture process nucleosynthesis is responsible for pernovae [4], the ν-driven wind of Type II supernovae (here- the production of elements heavier than iron, which is divided after SN II) is still regarded as the most possible candidate into slow (s)-process and rapid (r)-process, depending on the [5]. Almost all heavy elements are produced by both the s- competition between the β decay and the next neutron cap- and r-process. For example, the s-process contributes about ture event. These two neutron-capture process need to occur 85 percent of solar Ba and 3 percent of solar Eu, which are in different astrophysical sites because of the different physi- usually regarded as the represent elements of the s- and r- cal conditions they required. The s-process primarily occurs process, respectively [6]. in low- and intermediate-mass (M < 7M ) stars when they In low-mass AGB stars, the main neutron source is the evolve through their asymptotic giant branch (AGB) phase 12C(p,γ)13N(β)13C(α, n)16O reaction, which has been con- firmed by theory and observations [7,8]. The 13C-pocket is *Corresponding author (email: [email protected]) formed in a narrow region of the top of He-rich intershell †Recommended by HAN ZhanWen (Associate Editor)