# Presentation: 325722

## Abundance ratios in CEMP stars and the intermediate mass IMF

- Jennifer Johnson
- Ohio State University

## Why we care

- INTERNATIONAL MONETARY FUND

## Why we care

- IMF very dependent on the star formation conditions
- Quantities very dependent on the IMF
- Nucleosynthesis
- Integrated spectra/color/mass-to-light ratio
- Ionizing background
- IMF of first generation tells us what we should see today

## The Role of Mass

- 0.08  0.9 1.5             8.0                               40    --->
- Mass in solar masses

-  > Hubble

-  < Hubble

- No significant yields

- C, N, s-process elements

- C thru Fe group, r-process

- First to pollute. Individual SN events may be recorded in stars such as
- HE 0107-5240
- HE 1327-2326
- HE 1424-0241

- Impact on Galactic chemical evolution only after [Fe/H]> -2.6? -1.5?

- See poster by Melendez

- Poster: Gil-Pons, SN1.5

## AGB Nucleosynthesis depends on Mass

- Yields from Karakas (2003)

## Agreement with Observations  

- N-rich stars in MC (e.g. McSaveney et al. 2007)
- Li-rich intermediate mass S stars (e.g. Smith & Lambert 1989)
- 12C/13C in intermediate mass S stars (e.g. Vanture et al. 2007)
- CS 29528-041 (Sivarani et al. 2006)
- S-process elements (e.g. Gallino 1998)
- 12C/13C in red giants (thermohaline mixing? Charbonnel et al 2007, Stancliffe et al. 2007)
- Li in RGB stars (CPB)? (e.g. de la Reza et al. 1997)
- [C/N] ratios in CEMP stars (e.g. Busso & Gallino 2001)

- Dis

- Poster: Husti

## AGB binary systems

- AGB pollutes a lower mass star, creating a CEMP
- Binary is “chemically isolated” from the rest of the Universe
- Even though the AGB star could pollute its companion 1 Gyr ago, it’s all OK.
- CEMP=AGB pollution

- Poster: Masseron on CEMP-s/r+s, etc.

## The Meaning of CEMP

- Observations
- Beers et al. (1992)
- Hill et al. (2000)
- Preston & Sneden (2001)
- Rossi et al. 2005
- Lucatello et al (2005)
- Cohen et al. (2005)
- Aoki et al. (2006)

- Theory
- Lucatello et al. (2005)
- Komiya et al. (2007)
- Tumlinson (2007)

- Poster at this meeting

- Poster at this meeting

## [C/N] ratios in CEMP

- Suggests a high fraction of 2-3 solar mass stars created, higher than predicted by Salpeter IMF
- Outstanding issues
- Mass ratios of binaries in metal-poor environments
- Mass transfer efficiencies in binary systems with different mass ratios
- Do abundances of other elements agree with 2-3 mass AGB origin?

- Johnson, Herwig, Beers & Christlieb 2007

## Li and C in CEMP

- Li and C observed previous to our sample
- W/Masseron, Lucatello, Beers, Christlieb, Primas +.....
- 12 stars with strong G-bands
- Observed with UVES, set-up to cover Li feature at 6707 Angstroms
- S/N > 100
- Analysis by T. Masseron with TURBOSPECTRUM

- Poster: Korn

## Li observations in CEMP stars

- Li drops in CEMP stars before “normal field stars”.
- Suggest Li-poor material is being added

## 12C/13C ratios in CEMP

- 12C/13C ratios lower in CEMP, suggests 13C-rich material is being added.
- Not expected in low-mass stars but...

## Conclusions and Prospects

- Li-depleted material being added
- 12C/13C needs more study
- Additional elements (F, Na, O) and correlations between elements
- Observations of binarity, both CEMP and non-C-rich
- Observed mass ratios in binaries
- Better theoretical understanding of mixing
- Better theoretical understanding of binary formation and mass transfer

- Poster: Bisterzo

- Posters by Lai and Gonzalez Hernandez

- Posters by Lawlor and de Mihk