The Expansion of the X-Ray Nebula Around η Car

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Corcoran_2022_ApJ_937_122.pdf (1.49 MB)

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https://iopscience.iop.org/article/10.3847/1538-4357/ac8f27

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https://doi.org/10.3847/1538-4357/ac8f27
 http://hdl.handle.net/11603/26250

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UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
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UMBC Physics Department

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https://orcid.org/0000-0001-7515-2779

Date

2022-10-05

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journal articles
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Citation of Original Publication

Corcoran, Michael F. et al. "The Expansion of the X-Ray Nebula Around η Car." The Astrophysical Journal 937, no. 2 (October 5, 2022). https://doi.org/10.3847/1538-4357/ac8f27

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Abstract

The massive colliding wind binary system η Car is embedded in an X-ray emitting region having a characteristic temperature of a few million degrees, associated with ejecta produced during the 1840s, and in earlier outbursts. We use CHANDRA X-ray imaging observations obtained over the past two decades to directly measure the expansion of the X-ray nebula for the first time. A combined CHANDRA/ACIS image shows a faint, nearly uniform elliptic structure. This faint elliptical “shell” has a similar orientation and shape as the Homunculus nebula but is about 3 times larger. We measure proper motions of brighter regions associated with the X-ray emitting ring. We compare spectra of the soft X-ray emitting plasma in CHANDRA/ACIS and XMM-Newton PN observations and show that the PN observations indicate a decline in X-ray flux which is comparable to that derived from NICER observations. We associate the diffuse elliptical emission surrounding the bright X-ray “ring” with the blast wave produced during the Great Eruption. We suggest that the interaction of this blast wave with pre-existing clumps of ejecta produces the bright, broken X-ray emitting ring. We extrapolate the trend in X-ray energy back to the time of the Great Eruption using a simple model and show that the X-ray energy was comparable to the kinetic energy of the Homunculus, suggesting equipartition of energy between fast, low-density ejecta and slower, dense ejecta.