Astron. Astrophys. 320, 568-574 (1997)

1. Introduction

Luminous Blue Variables (LBVs) are often found in small circumstellar nebulae, which contain the mass lost by these evolved supergiants (Nota et al. 1995). With an initial mass 50 , these stars start as main-sequence O stars and evolve towards cooler temperatures at the end of hydrogen-core burning. Following this track they enter the LBV phase when they approach the Humphreys-Davidson limit (e.g. Langer et al. 1994; García-Segura et al. 1996). The Humphreys-Davidson limit is an empirical upper boundary in the HR diagram (Humphreys & Davidson 1979). Stars near this boundary are very unstable and show the highest mass-loss rates observed, several . Losing more and more mass via continuous stellar winds and violent outbursts or eruptions, LBVs never reach the red supergiant phase but enter the Wolf-Rayet state after yr in the LBV phase (Humphreys & Davidson 1994). The copious mass loss associated with the violent eruptions is responsible for the formation of a circumstellar nebula. An excellent example is given by the LBV Carinae, around which the LBV nebula (LBVN) corresponds to eruptions mainly in 1840-1860 (Polcaro and Viotti 1993; Viotti 1995).

The star HR Carinae (also known as HD 90177, SAO 238005, He 3-407) is one of the few LBVs known in our Galaxy. Its spectral type varies from B2 I to B9 I ; strong Balmer, Fe II and [Fe II ] emission lines are observed, with the Balmer and Fe II lines showing P Cygni profiles (Carlson & Henize 1979; Hutsemékers & Van Drom 1991). The distance to the star has been derived using two different methods which give consistent results: kinematic distance kpc (Hutsemékers & Van Drom 1991), and reddening distance kpc (van Genderen et al. 1991). Therefore, HR Car has a luminosity of , comparable to the other LBVs. The circumstellar nebula around HR Car was not discovered until 1991, making it one of the newest member of LBVNs (Hutsemékers & Van Drom 1991). The origin and shape of the nebula around HR Car has been discussed by Hutsemékers (1994). A high-resolution image and a spectropolarimetric study have been presented by Clampin et al. (1995).

We have obtained deep H CCD images and high-dispersion, long-slit echelle observations of the nebula around HR Car. The images are used to examine the structure of the circumstellar nebula and large-scale gaseous environment of HR Car. The echelle data are used to study the internal motion of the HR Car nebula. In this paper we report our analysis of the environment, kinematics, age, and evolution of the nebula around the LBV HR Car.

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998
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