Changes in the Na D1 Absorption Components of η Carinae Provide Clues on the Location of the Dissipating Central Occulter
| Autor: | Connor S. Pickett, Noel D. Richardson, Theodore R. Gull, D. John Hillier, Henrik Hartman, Nour Ibrahim, Alexis M. Lane, Emily Strawn, Augusto Damineli, Anthony F. J. Moffat, Felipe Navarete, Gerd Weigelt |
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| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | The Astrophysical Journal. 937:85 |
| ISSN: | 1538-4357 0004-637X |
| DOI: | 10.3847/1538-4357/ac898f |
| Popis: | The Na D absorption doublet in the spectrum of $\eta$ Carinae is complex, with multiple absorption features associated with the Great Eruption (1840s), the Lesser Eruption (1890s), and 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 $\lambda$5876 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}$ that 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 $\eta$ 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, $\eta$ Car has been gradually brightening demonstrated 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 red-shifted component likely originates in an extended foreground structure consistent with a previous ultraviolet spectral survey in the Carina Nebula. Comment: 8 figures, 13 pages plus online data, accepted to ApJ |
| Databáze: | OpenAIRE |
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