CaltechAUTHORS
Published December 10, 2021 | Version Published
Journal Article Open

Eta Carinae: A Tale of Two Periastron Passages

Creators

  • 1. ROR icon Goddard Space Flight Center
  • 2. ROR icon Universidade de São Paulo
  • 3. ROR icon Catholic University of America
  • 4. ROR icon University of Maryland, Baltimore County
  • 5. ROR icon Malmö University
  • 6. ROR icon University of Pittsburgh
  • 7. ROR icon San Jose State University
  • 8. ROR icon University of Montreal
  • 9. ROR icon Centre for Research in Astrophysics of Québec
  • 10. ROR icon Infrared Processing and Analysis Center
  • 11. ROR icon University of Leeds
  • 12. ROR icon University of Sheffield
  • 13. ROR icon Embry–Riddle Aeronautical University
  • 14. ROR icon University of Birmingham
  • 15. ROR icon Max Planck Institute for Radio Astronomy

Abstract

Since 2002, the far-ultraviolet (FUV) flux (1150–1680 Å) of Eta Carinae, monitored by the Hubble Space Telescope/Space Telescope Imaging Spectrograph, has increased by an order of magnitude. This increase is attributed to partial dissipation of a line-of-sight (LOS) occulter that blocks the central core of the system. Across the 2020 February periastron passage, changes in the FUV emission show a stronger wavelength dependence than occurred across the 2003 July periastron passage. Across both periastron passages, most of the FUV spectrum dropped in flux then recovered a few months later. The 2020 periastron passage included enhancements of FUV flux in narrow spectral intervals near periastron followed by a transient absorption and recovery to pre-periastron flux levels. The drop in flux is due to increased absorption by singly ionized species as the secondary star plunges deep into the wind of the primary star, which blocks the companion's ionizing radiation. The enhanced FUV emission is caused by the companion's wind-blown cavity briefly opening a window to deeper layers of the primary star. This is the first time transient brightening has been seen in the FUV comparable to transients previously seen at longer wavelengths. Changes in resonance line-velocity profiles hint that the dissipating occulter is associated with material in LOS moving at −100 to −300 km s⁻¹, similar in velocity of structures previously associated with the 1890s lesser eruption.

Additional Information

© 2021. The American Astronomical Society. Received 2021 June 4; revised 2021 August 27; accepted 2021 August 30; published 2021 December 14. We thank the referee for much effort and useful comments that improved the presentation especially for those less familiar with η Car. We acknowledge funding from HST programs 15611 and 15992, which were accepted as supplementary observations associated with Chandra X-ray Observatory programs 20200564 and 21200197. M.F.C. is supported under the CRESST-II cooperative agreement #80GSFC17M0002 with the NASA/Goddard Space Flight Center. A.D. received funding from FAPESP 2019/02029-2. F.N. acknowledges FAPESP for support through process 2017/18191-8. A.J.F.M. is grateful for financial aid from NSERC (Canada). Facility: HST(STIS). -

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Published - Gull_2021_ApJ_923_102.pdf

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Additional details

Identifiers

Eprint ID
112781
Resolver ID
CaltechAUTHORS:20220107-81089900

Funding

NASA Hubble Fellowship
GO-15611
NASA Hubble Fellowship
GO-15992
NASA
80GSFC17M0002
Fundação de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP)
2019/02029-2
Fundação de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP)
2017/18191-8
Natural Sciences and Engineering Research Council of Canada (NSERC)

Dates

Created
2022-01-09
Created from EPrint's datestamp field
Updated
2022-01-09
Created from EPrint's last_modified field

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Caltech groups
Infrared Processing and Analysis Center (IPAC)