| Texto completo | |
| Autor(es): |
Groh, J. H.
[1, 2, 3]
;
Hillier, D. J.
[1]
;
Damineli, A.
[3]
;
Whitelock, P. A.
[4, 5, 6]
;
Marang, F.
[4]
;
Rossi, C.
[7]
Número total de Autores: 6
|
| Afiliação do(s) autor(es): | [1] Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 - USA
[2] Max Planck Inst Radioastron, D-53121 Bonn - Germany
[3] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508900 Sao Paulo - Brazil
[4] S African Astron Observ, ZA-7935 Observatory - South Africa
[5] Univ Cape Town, Dept Math & Appl Math, Natl Astrophys & Space Sci Programme, ZA-7701 Rondebosch - South Africa
[6] Univ Cape Town, Dept Astron, ZA-7701 Rondebosch - South Africa
[7] Univ Roma La Sapienza, I-00185 Rome - Italy
Número total de Afiliações: 7
|
| Tipo de documento: | Artigo de Revisão |
| Fonte: | ASTROPHYSICAL JOURNAL; v. 698, n. 2, p. 1698-1720, JUN 20 2009. |
| Citações Web of Science: | 91 |
| Resumo | |
We present a detailed spectroscopic analysis of the luminous blue variable (LBV) AG Carinae (AG Car) during the last two visual minimum phases of its S-Dor cycle (1985-1990 and 2000-2003). The analysis reveals an overabundance of He, N, and Na, and a depletion of H, C, and O, on the surface of the AG Car, indicating the presence of a CNO-processed material. Furthermore, the ratio N/O is higher on the stellar surface than in the nebula. We found that the minimum phases of AG Car are not equal to each other, since we derived a noticeable difference between the maximum effective temperature achieved during 1985-1990 (22,800 K) and 2000-2001 (17,000 K). Significant differences between the wind parameters in these two epochs were also noticed. While the wind terminal velocity was 300 km s(-1) in 1985-1990, it was as low as 105 km s(-1) in 2001. The mass-loss rate, however, was lower from 1985-1990 (1.5 x 10(-5) M(circle dot) yr(-1)) than from 2000-2001 (3.7 x 10(-5) M(circle dot) yr(-1)). We found that the wind of AG Car is significantly clumped (f similar or equal to 0.10-0.25) and that clumps must be formed deep in the wind. We derived a bolometric luminosity of 1.5 x 10(6) L(circle dot) during both minimum phases which, contrary to the common assumption, decreases to 1.0 x 10(6) L(circle dot) as the star moves toward the maximum flux in the V band. Assuming that the decrease in the bolometric luminosity of AG Car is due to the energy used to expand the outer layers of the star, we found that the expanding layers contain roughly 0.6-2 M(circle dot). Such an amount of mass is an order of magnitude lower than the nebular mass around AG Car, but is comparable to the nebular mass found around lower-luminosity LBVs and to that of the Little Homunculus of Eta Car. If such a large amount of mass is indeed involved in the S Dor-type variability, we speculate that such instability could be a failed Giant Eruption, with several solar masses never becoming unbound from the star. (AU) | |
| Processo FAPESP: | 02/11446-5 - Modelagem de ventos e atmosferas de estrelas tipo LBV e WR |
| Beneficiário: | Jose Henrique Groh de Castro Moura |
| Modalidade de apoio: | Bolsas no Brasil - Doutorado Direto |