An Old Bipolar Shell Associated with η Carinae

Bohigas, J.; Tapia, M.; Ruiz, M. T.; Roth, M.
Bibliographical reference

Astrophysical Plasmas: Codes, Models, and Observations, Proceedings of the conference held in Mexico City, October 25-29, 1999, Eds. Jane Arthur, Nancy Brickhouse, and José Franco, Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias), Volume 9, p. 343

Advertised on:
5
2000
Number of authors
4
IAC number of authors
0
Citations
0
Refereed citations
0
Description
Continuum subtracted dereddened images in several emission lines reveal the existence of an extended bipolar shell around η Carinae. It is best seen in the light of [ion{O}{3}]5007. The geometrical disposition and mass of the shell-between 5 and 7 Modot-suggest that it was produced by mass outflows from this star. The approximate size and dynamic age of the bipolar shell are 100 × 45 arcsec (1.3 × 0.5 pc) and 13000/V7 yr, where V7 is the mean expansion velocity in 100 km s-1. Spectroscopic observations show that the bipolar shell is mildly excited, photoionized and composed of material that has not been through nuclear processing. Several nitrogen-rich knots, obviously made of material that has been through the CNO cycle, were also discovered. These are between 64 and 100 arcsec away from η Carinae, which implies that they were either ejected at approximately the same time as the Homunculus (during the ~ 1840 brightening of this star) but with much larger velocities, or centuries before this event. The bipolar shell and the distant nitrogen-rich knots should provide important clues regarding the time elapsed between the last pre-LBV and the first LBV eruption of η Carinae, as well as on the dynamics of mass ejections from this object. This information can be consequential in the understanding of the last evolutionary stages of the most massive stars. A full account of this work can be found in Bohigas et al. (2000; MNRAS, 312, 295)