HCT/HESP study of two carbon stars from the LAMOST survey
  Carbon stars, enhanced in carbon and neutron-capture elements, provide wealth
of information about the nucleosynthesis history of the Galaxy. In this work,
we present the first ever detailed abundance analysis of 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
Hanle Echelle Spectrograph (HESP) attached to the Himalayan Chandra Telescope
(HCT), IAO, Hanle. The stellar atmospheric parameters (T$_{eff}$, logg,
micro-turbulance ${\zeta}$, 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, C, N, O, Na,
$\alpha$-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
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 AGB companions for both
the stars. Kinematic analysis shows that LAMOSTJ151003.74+305407.3 belongs to
the Galactic halo population and LAMOSTJ091608.81+230734.6 to the disc
population.
