2021MNRAS.502.1008S

Carbon stars, enhanced in carbon and neutron-capture elements, provide a wealth of information about the nucleosynthesis history of the Galaxy. In this work, we present the first ever detailed abundance analysis of the carbon star LAMOSTJ091608.81+230734.6 and a detailed abundance analysis of neutron-capture elements for the object LAMOSTJ151003.74+305407.3. Updates on the abundances of elements C, O, Mg, Ca, Cr, Mn and Ni for LAMOSTJ151003.74+305407.3 are also presented. Our analysis is based on high-resolution spectra obtained using the Hanle Echelle Spectrograph (HESP) attached to the Himalayan Chandra Telescope (HCT) at the Indian Astronomical Observatory, Hanle. The stellar atmospheric parameters (T_eff, log g, microturbulance ζ, metallicity [Fe/H]) are found to be (4820, 1.43, 1.62, -0.89) and (4500, 1.55, 1.24, -1.57) for these two objects, respectively. The abundance estimates of several elements, namely C, N, O, Na, α-elements, Fe-peak elements and neutron-capture elements Rb, Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm and Eu, are presented. Our analysis shows the star LAMOSTJ151003.74+305407.3 to be a CEMP-r/s star, and LAMOSTJ091608.81+230734.6 to be a CH giant. We have examined if the i-process model yields ([X/Fe]) of heavy elements could explain the observed abundances of the CEMP-r/s star based on a parametric model-based analysis. The negative values obtained for the neutron-density-dependent [Rb/Zr] ratio confirm former low-mass asymptotic giant branch companions for both stars. Kinematic analysis shows that LAMOSTJ151003.74+305407.3 belongs to the Galactic halo population while LAMOSTJ091608.81+230734.6 belongs to the disc population.