12 C/ 13 C in atmospheres of red giants and peculiar stars

1. 12C/13C in atmospheres of red giants and peculiar stars Yakiv V.Pavlenko1,2 1Main Astronomical Observatory of National Academy of Sciences, 27 Zabolotnoho, Kyiv-127, 03680 Ukraine 2Centre for Astrophysics Research, University of Hertfordshire, College lane, Hatfield, AL10 9AB, UK We carry out determination of carbon isotopic ratios in atmospheres of some evolved and ultracool objects of the disc of Galaxy and red giants of globular clusters. Analysis of 12CO and 13CO bands was carried out using fits of the synthetic spectra to the observed spectra. Procedure Sakurai's object (V4334 Sgr) 'Best solutions' were found at the function min: f(h,s,b,x)=(Hsynt-Hobs)2 h – shift corr., s – normalis. const., b- broadening param., x- something else. V4334 Sgr is a low mass star undergoing a very late thermal pulse(VLTP). After traversing the “knee'' on post AGB evolutionary track the star experiences a final He flash on the way to white dwarf cooling track. Pavlenko & Geballe (2002, AA, 390, 621) found evidences that the hot dust produces the significant excess continuum at long wavelengths ( > 2 m). Model atmospheres Sam12 (Pavlenko 2002, AR,47,59) Later Pavlenko, Geballe, Evans et al. (2004, AA, 417, L39) from the fits to 2.3 m CO bands obtained 12C/13C = 4 +/- 1 for the July, 1998 spectrum. We account the dust emission. Our 12C/13C is consistent with the interpretation of V4334 Sgr as an object that undergone VLTP. Line lists: CO (Goorvitch 1994,ApJS,95,535), Kurucz (1994, SAO Rept.), VALD (Kupka et at al.(1999), H2O (Partrige & Schwenke 1997, Chem.Phys.,106,4618). Pavlenko, Jones & Longmore (MNRAS, 2003, 345, 311) fit the synthetic 2.3 m CO bands to the observed spectra of a few RG of the GC of different metallicity. We found: -- our giants of M3 and M13 ([Fe/H]< -1.3 dex) have about the same 12C/13C, -- we get some evidence about lower 12C/13C in gants of lower [Fe/H], -- giants of more metal rich clusters show larger dispersion of 12C/13C, -- more evolved stars show lower carbon abundances. Ultracool dwarfs Pavlenko & Jones (2003, AA, 397, 967) compared observed and theoretical spectra of CO bands of some M-dwarfs. We found the 2.375m 13CO band is more useful for the carbon isotopic ratio determination becouse is does suffer less contamination by water. We show the contamination by water vapour lines provides even more problems for the region of CO bands v1) at 4.5 mSee more details in Jones, Pavlenko, Viti et al. (2005, MNRAS, 358. 105) for the cooler objects. Red giants of globular clusters