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Letter to the Editor
A two-component infrared nebula around HR Car *
R.H.M. Voors 1, 2,
L.B.F.M. Waters 3, 4,
N.R. Trams 5 and
H.U. Käufl 6
Received 21 January 1996 / Accepted 4 February 1997
We present mid-infrared imaging of the LBV HR Car and its surrounding nebula. The 10 m broad-band N image reveals a geometry which is not point symmetric with respect to the central star on an arcsecond scale. The 12.8 m narrow-band [Ne II ] image shows a clumpy structure which does not follow the N-band distribution. In addition, we detect a faint and probably clumpy outer nebula about across.
The morphology of the infrared nebula and in particular its asymmetry is not at all in agreement with the large-scale structures as seen in optical images. Three different episodes of shell ejection can now be distinguished for HR Car: the arc-like structures seen in the optical, about across, the faint IR nebula seen in the N-band, about across, and the small, irregular nebula less than across. The main conclusion we draw from this is that the geometry of mass-ejections in HR Car is highly time-dependent and that multiple shell ejections can occur in LBVs.
The distance of the small IR nebula from the central star can be well explained by a dust shell that is composed of silicates and is in radiative equilibrium with the central star.
Key words: HR Car Circumstellar matter Infrared: stars Mass-loss
Send offprint requests to: R.H.M. Voors
Online publication: June 30, 1998