THE BIPOLAR HR CARINAE NEBULA - DYNAMICS AND CHEMICAL ABUNDANCES

We present the results of a new set of medium resolution spectroscopic observations and high-resolution coronographic images of the nebula a round the Galactic luminous blue variable (LBV) HR Carinae. The observ ations were carried out at the ESO/NTT (La Silla) in 1995 May and 1996 January. The nebular morphology and kinematics confirm that the nebul a around HR Carinae is truly bipolar and very reminiscent of the eta C arinae nebula. The previously identified ''filaments'' outline the edg es of two symmetrical expanding bubbles, originating from the star and located, respectively, in the NW and SE quadrants. The small compact inner nebula, a few arcsec in size, previously detected, represents th e ''waist'' of the bipolar distribution. The orientation in the images and the kinematical study have allowed us to define the true orientat ion of the bubbles, whose major axis lies at an angle of similar or eq ual to 50 degrees with the plane of the sky, at an inclination of appr oximately 30 degrees on the line of sight. The maximum projected expan sion velocity is of the order of similar or equal to 100 km s(-1). In the light of these new kinematical data, we revise the dynamical times cale to a younger age of similar or equal to 5000 yr. The nebula aroun d HR Carinae is relatively young and fast, at variance with other well known LBV nebulae such as AG Carinae's. Spectroscopically, the nebula is of low excitation with CO mi absent, and CN nl fairly strong. [Ni II] lambda 6667 is detected, but only in the inner regions (less than or equal to 5 ''). We find that the electron density increases from 40 0 cm(-3) in the outer regions to more than 10(4) cm(-3) in the innermo st regions. An analysis of the chemical abundances in different region s of the nebula finds that N is over-abundant, indicating that the neb ula is composed of CNO processed stellar material. We find that the fi lamentary H II region, seen to the NW of HR Carinae, is at the same di stance and is composed of material with typical H II region abundances , and has a morphology that suggests it has been shaped by the wind of HR Carinae.