A detailed spectroscopy of the carbon-rich star BD +57° 2161

¹ Institute of Atomic Physics and Spectroscopy, University of Latvia, Raiņa bulvāris 19, 1586 Rīga, Latvia e-mail: zacs@latnet.lv
² N. Copernicus Astronomical Center, ul. Rabiańska 8, 87-100 Toruń, Poland e-mail: schmidt@ncac.torun.pl
³ Special Astrophysical Observatory and Isaac Newton Institute of Chile, SAO Branch, Nizhnij Arkhyz, 369167, Russia e-mail: faig@sao.ru, gala@sao.ru
⁴ ICAMER, National Academy of Sciences of Ukraine, 361605 Peak Terskol, Kabardino-Balkaria, Russia
⁵ Shamakhy Astrophysical Observatory, National Academy of Sciences of Azerbaijan, Azerbaijan
⁶ Korean Astronomy Observatory, Optical Astronomy Division, 61-1, Whaam-Dong, Yuseong-Gu, Daejon, 305-348, Korea e-mail: gala@boao.re.kr
⁷ Vilnius University Observatory, Ciurlionio 29, Vilnius 2009, Lithuania e-mail: julius.sperauskas@ff.vu.lt

Received: 23 November 2004
Accepted: 9 May 2005

Abstract

An LTE abundance analysis based on high-resolution spectra is presented for the carbon-rich star BD +57° 2161, whose evolutionary status is unknown. With  dex and a mean s-process overabundance of  dex the peculiar atmospheric composition of BD +57° 2161 is confirmed. The ¹²C/¹³C abundance ratio was found to be about 10. The mild iron deficiency, , supports the idea that BD +57° 2161 could be an old-disk-population object. Radial-velocity measurements confirm the binary nature of the star. Therefore the peculiar chemical composition could be due to the mass transfer from the secondary - AGB star in the past. Orbital parameters are estimated for another star of this group, BD +75° 348.