Publication Date

9-1-2023

Document Type

Article

Publication Title

Astrophysical Journal

Volume

954

Issue

1

DOI

10.3847/1538-4357/ace596

Abstract

Eta Carinae ( • Car) exhibits a unique set of P Cygni profiles with both broad and narrow components. Over many decades, the spectrum has changed - there has been an increase in observed continuum fluxes and a decrease in Fe ii and H i emission-line equivalent widths. The spectrum is evolving toward that of a P Cygni star such as P Cygni itself and HDE 316285. The spectral evolution has been attributed to intrinsic variations such as a decrease in the mass-loss rate of the primary star or differential evolution in a latitudinal-dependent stellar wind. However, intrinsic wind changes conflict with three observational results: the steady long-term bolometric luminosity; the repeating X-ray light curve over the binary period; and the constancy of the dust-scattered spectrum from the Homunculus. We extend previous work that showed a secular strengthening of P Cygni absorptions by adding more orbital cycles to overcome temporary instabilities and by examining more atomic transitions. cmfgen modeling of the primary wind shows that a time-decreasing mass-loss rate is not the best explanation for the observations. However, models with a small dissipating absorber in our line of sight can explain both the increase in brightness and changes in the emission and P Cygni absorption profiles. If the spectral evolution is caused by the dissipating circumstellar medium, and not by intrinsic changes in the binary, the dynamical timescale to recover from the Great Eruption is much less than a century, different from previous suggestions.

Funding Number

TM2-23003X

Funding Sponsor

National Science Foundation

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Physics and Astronomy

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