THE ASTROPHYSICAL JOURNAL, 460:L49[–]L52, 1996 March 20
© 1996. The American Astronomical Society. All rights reserved. Printed in
U.S.A.
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                                §1. INTRODUCTION

     [&eegr;] Carinae is one of the most luminous stellar objects of our
Galaxy, with a luminosity of 5 × 106 L[&sun;] (Andrisse, Donn, & Viotti 1978).
If single, it is also one of the most massive stars known, having a mass of 120
M[&sun;]. It is believed to be in the luminous blue variable (LBV) stage, a
short-lived strongly mass-losing phase, which causes a deep erosion in the
outer layers of massive stars before they enter the Wolf-Rayet phase. [&eegr;]
Car shares many features with other LBVs. In addition, this star underwent
giant bursts in the last centuries. However, the S Dor[–]type
variability, typical of LBV stars, is not clear in this object (van Genderen,
de Groot, & Thé 1994). The main characteristic of the S Dor behavior is
alternating states of quiescence, in which the star is fainter and hotter, and
eruptive phases, in which it is cooler and brighter, in timescales of years to
tens of years (van Genderen & Thé 1984; Humphreys & Davidson 1994; Lamers
1995). Occasional shell episodes were observed in [&eegr;] Car (see Damineli et
al. 1995 for references). During those events, the high-excitation lines
characteristic of the [“]normal spectrum[”] ([Ne III], [Fe III],
[Ar III], and He I) faded out. This behavior has been suggested as being
related to S Dor variability, although the associated photometric variations
were not evident.

     The last shell event of 1992 (Damineli et al. 1995; Baratta, Damineli, &
Viotti 1993) was followed by an enhancement of flux in the radio wavelength
range (Duncan et al. 1995) and by the reappearence of the stellar source in
hard X-rays (Corcoran et al. 1995). A binary scenario was sometimes invoked to
explain some features of the optical light curve (van Genderen et al. 1994),
but this hypothesis is not supported by the observations.

     The Homunculus is mainly a reflecting nebula (Humphreys & Davidson 1994;
van Genderen & Thé 1984), which is apparently produced by a bipolar outflow
(Warren-Smith et al. 1979; Hyland et al. 1979; Mitchell et al. 1983; Allen &
Hillier 1993; Meaburn, Walsh, & Wolstencroft 1993; Frank, Balick, & Davidson
1995). Accurate maps of this nebula could shed some light on the mass ejection
mechanism of this highly obscured star.

     In this Letter, I propose a technique to map in detail the geometry of the
Homunculus and to check the coherent periodicity of the central star, which
been strongly suggested by recent data.

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