Eta Carinae: A Tale of Two Periastron Passages

• Published in: The Astrophysical journal Vol. 923; no. 1; pp. 102 - 121
• Main Authors: Gull, Theodore R., Navarete, Felipe, Corcoran, Michael F., Damineli, Augusto, Espinoza, David, Hamaguchi, Kenji, Hartman, Henrik, Hillier, D. John, Madura, Thomas, Moffat, Anthony F. J., Morris, Patrick, Nielsen, Krister, Pittard, Julian M., Pollock, Andrew M. T., Richardson, Noel D., Russell, Christopher M. P., Stevens, Ian R., Weigelt, Gerd
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center The American Astronomical Society 01-12-2021; IOP Publishing
• Subjects: Absorption; Astronomy; Astronomy and Astrophysics; Astrophysics; Binary stars; Brightening; Emission; Fluctuations; Hubble Space Telescope; Ionizing radiation; Line of sight; Massive stars; Resonance lines; Space and Planetary Science; Space telescopes; Stellar winds; Velocity; Velocity distribution; Wavelengths; Wind
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/ac22a6

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