Radial velocity measurements , BVR _ { C } photometry , and high-resolution spectroscopy in the wavelength region from blue to near infrared are employed in order to clarify the evolutionary status of the carbon-enhanced metal-poor star HD 112869 with unique ratio of carbon isotopes in the atmosphere .
An LTE abundance analysis was carried out using the method of spectral synthesis and new self consistent 1D atmospheric models .
The radial velocity monitoring confirmed semiregular variations with a peak-to-peak amplitude of about 10 km s ^ { -1 } and a dominating period of about 115 days .
The light , color and radial velocity variations are typical of the evolved pulsating stars .
The atmosphere of HD 112869 appears to be less metal-poor than reported before , [ Fe/H ] = - 2.3 \pm 0.2 dex .
Carbon to oxygen and carbon isotope ratios are found to be extremely high , C/O \simeq 12.6 and ^ { 12 } C / ^ { 13 } C \gtrsim 1500 , respectively .
The s–process elements yttrium and barium are not enhanced , but neodymium appears to be overabundant .
The magnesium abundance seems to be lower than the average found for CEMP stars , [ Mg/Fe ] < +0.4 dex .
HD 112869 could be a single low mass halo star in the stage of asymptotic giant branch evolution .