  We present the abundance analyses of 7 Carbon enhanced metal-poor (CEMP)
stars to understand the origin of carbon in them. We used high-resolution
optical spectra to derive abundances of various elements. We also used
low-resolution Near-Infrared (NIR) spectra to derive the abundance of O and
12C/13C from the CO molecular band and compared their values with those derived
from high-resolution optical spectra. We identified a good agreement between
the values. Thus, in cool CEMP stars, the NIR observations complement the
high-resolution optical observations to derive the oxygen abundance and the
12C/13C ratio. This enables us to probe fainter cool CEMP stars using NIR
spectroscopy. C, N, O abundances of all the program stars in this study show
abundances that are consistent with binary mass transfer from a low-mass
low-metallicity Asymptotic Giant Branch (AGB) companion which is further
supported by the presence of enhancement in neutron-capture elements and
detection of radial velocity variation. One of the stars show abundance
patterns similar to a CEMP-s star whereas the abundance pattern of the rest of
the stars satisfy the criteria required to classify them as CEMP-r/s stars. The
sub-classification of some of the stars studied here is revisited. The
abundance of neutron capture elements in these CEMP-r/s stars resembles to that
of i-process models where proton ingestion episodes in the companion low-mass
low-metallicity AGB stars produce the necessary neutron density required for
the onset of i-process.
