|
| | | | |
| | | |
| Stat |
Members: 3657
Articles: 2'599'751
Articles rated: 2609
09 October 2024 |
|
| | | | |
|
Article overview
| |
|
|
Chemical analysis of carbon stars in the Local Group: I. The Small Magellanic Cloud and the Sagittarius dwarf spheroidal galaxy | | P. De Laverny
; C. Abia
; I. Dominguez
; B. Plez
; O. Straniero
; R. Wahlin
; K. Eriksson
; U.G. Joergensen
; | | Date: |
5 Oct 2005 | | Subject: | astro-ph | | Affiliation: | OCA), C. Abia, I. Dominguez, B. Plez (GRAAL | | Abstract: | We present the first results of our ongoing chemical study of carbon stars in the Local Group of galaxies. We used spectra obtained with UVES at the 8.2 m Kueyen-VLT telescope and a new grid of spherical model atmospheres for cool carbon-rich stars which include polyatomic opacities, to perform a full chemical analysis of one carbon star, BMB-B~30, in the Small Magellanic Cloud (SMC) and two, IGI95-C1 and IGI95-C3, in the Sagittarius Dwarf Spheroidal (Sgr dSph) galaxy. Our main goal is to test the dependence on the stellar metallicity of the s-process nucleosynthesis and mixing mechanism occurring in AGB stars. For these three stars, we find important s-element enhancements with respect to the mean metallicity ([M/H]), namely [s/M]$approx$+1.0, similar to the figure found in galactic AGB stars of similar metallicity. The abundance ratios derived between elements belonging to the first and second s-process abundance peaks, corresponding to nuclei with a magic number of neutrons N=50 (88Sr, 89Y, 90Zr) and N=82 (138Ba, 139La, 140Ce, 141Pr), agree remarkably well with the theoretical predictions of low mass (M $<3$~M$\_odot$) metal-poor AGB nucleosynthesis models where the main source of neutrons is the $^{13}$C$(alpha,n)^{16}$O reaction activated duringthe long interpulse phase, in a small pocket located within the He-rich intershell. The derived C/O and $^{12}$C/$^{13}$C ratios are, however, more difficult to reconcile with theoretical expectations. Possible explanations, like the extrinsic origin of the composition of these carbon stars or the operation of a non-standard mixing process during the AGB phase (such as the {it cool bottom process}), are discussed on the basis of the collected observational constraints. | | Source: | arXiv, astro-ph/0510131 | | Services: | Forum | Review | PDF | Favorites | |
|
|
No review found.
Did you like this article?
Note: answers to reviews or questions about the article must be posted in the forum section.
Authors are not allowed to review their own article. They can use the forum section.
|
| |
|
|
|
REGISTER