Details

Autor(en) / Beteiligte

• Pickett, Connor S.
• Richardson, Noel D.
• Gull, Theodore R.
• Hillier, D. John
• Hartman, Henrik
• Ibrahim, Nour
• Lane, Alexis M.
• Strawn, Emily
• Damineli, Augusto
• Moffat, Anthony F. J.
• Navarete, Felipe
• Weigelt, Gerd

Titel

Changes in the Na D1 Absorption Components of η Carinae Provide Clues on the Location of the Dissipating Central Occulter

Ist Teil von

• The Astrophysical journal, 2022-10, Vol.937 (2), p.85

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2022

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• The Na D absorption doublet in the spectrum of η Carinae is complex, with multiple absorption features associated with the Great Eruption (1840s), the Lesser Eruption (1890s), and the interstellar clouds. The velocity profile is further complicated by the P Cygni profile originating in the system’s stellar winds and blending with the He i λ5876 profile. The Na D profile contains a multitude of absorption components, including those at velocities of −145 km s−1, −168 km s−1, and +87 km s−1, which we concentrate on in this analysis. Ground-based spectra recorded from 2008 to 2021 show significant variability of the −145 km s−1 absorption throughout long-term observations. In the high-ionization phases of η Carinae prior to the 2020 periastron passage, this feature disappeared completely but briefly reappeared across the 2020 periastron, along with a second absorption at −168 km s−1. Over the past few decades, η Carinae has been gradually brightening, which is shown to be caused by a dissipating occulter. The decreasing absorption of the −145 km s−1 component, coupled with similar trends seen in absorptions of ultraviolet resonant lines, indicate that this central occulter was possibly a large clump associated with the Little Homunculus or another clump between the Little Homunculus and the star. We also report on a foreground absorption component at +87 km s−1. Comparison of Na D absorption in the spectra of nearby systems demonstrates that this redshifted component likely originates in an extended foreground structure consistent with a previous ultraviolet spectral survey in the Carina Nebula.