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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                      The 5.52 Year Cycle of Eta Carinae 1

                               Augusto Damineli

Instituto Astronômico e Geofísico da USP, CP 9638, 01065-970 São Paulo, Brazil;
                         damineli@carina.iagusp.usp.br

               Received 1995 October 3; accepted 1995 December 11

                                    ABSTRACT

     I have discovered spectroscopic variations correlated with the photometric
near-infrared (NIR) light curve in [&eegr;] Carinae. The fading of the
high-excitation lines is coincident with the peaks in the NIR light curve,
strongly resembling an S Doradus type of variability. The cycle, however, is
highly stable, and the 5.52 yr period fits well all the shell episodes reported
in the last 50 years. This period also recovers the three historical bursts of
the last century, in phase with the present low-amplitude oscillations, which
suggests a connection between the S Doradus cycle and the giant bursts. The
present data reveal that [&eegr;] Car is continuously varying in the He I
[&lgr;]10830 line by thousands of solar luminosities. The last spectra in this
line show that the low-excitation phase is already in progress. A test for the
strict periodicity will be the confirmation of the central phase epoch of the
next shell event, predicted to occur in 1997 December. A very sensitive mapping
technique is also proposed for this occasion, in order to prove Homunculus
geometry.

Subject headings: stars: individual ([&eegr;] Carinae)[—]stars:
variables: other (luminous blue variables)[—]stars: emission-line, Be

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CONTENTS

   * 1. INTRODUCTION
   * 2. THE 5.52 YEAR SPECTRAL CYCLE
   * 3. PHOTOMETRIC OSCILLATIONS
   * 4. DISCUSSION
   * ACKNOWLEDGMENTS
   * REFERENCES
   * FIGURES
   * TABLES
   * REFERENCES TO THIS ARTICLE

FOOTNOTES

     1 Based on data collected at CNPq/Laboratório Nacional de Astrofísica,
Brazil.

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