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| Paper: |
Hot and Cool: Stellar Parameters of the Prototype LBV AG Carinae across the HR Diagram |
| Volume: |
425, Hot and Cool: Bridging Gaps in Massive Star Evolution |
| Page: |
215 |
| Authors: |
Groh, J. H. |
| Abstract: |
I discuss the temporal evolution of the stellar parameters of the prototype LBV AG Carinae, which has been the most variable object among the Galactic LBVs during the last 20 years. Based on a detailed spectroscopic analysis using the radiative transfercode CMFGEN, we found that AG Car was at different sides of the bi-stability limit in different epochs, as predicted by Vink & de Koter (2002). Contrary to the common assumption by the community, we found that the bolometric luminosity of AG Car decreases from 1.5×106 Lsun to 1.0×106 Lsun as the star moves towards maximum flux in the V band. To explain such decrease, the expansion of about 0.6–2 Msun is needed, which is comparable to the nebular mass found around lower-luminosity LBVs and to that of the Little Homunculus of η Car. We speculate that the S/,Dor-type instability could be a failed Giant Eruption, with several solar masses never becoming unbound from the star. |
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