Detection of Pristine Circumstellar Material of the Cassiopeia A Supernova

Abstract

Cassiopeia A is a nearby young supernova remnant that provides a unique laboratory for the study of core-collapse supernova explosions. Cassiopeia A is known to be a Type IIb supernova from the optical spectrum of its light echo, but the immediate progenitor of the supernova remains uncertain. Here we report results of near-infrared, high-resolution spectroscopic observations of Cassiopeia A where we detected the pristine circumstellar material of the supernova progenitor. Our observations revealed a strong emission line of iron (Fe) from a circumstellar clump that has not yet been processed by the supernova shock wave. A comprehensive analysis of the observed spectra, together with an HST image, indicates that the majority of Fe in this unprocessed circumstellar material is in the gas phase, not depleted onto dust grains as in the general interstellar medium. This result is consistent with a theoretical model of dust condensation in material that is heavily enriched with CNO-cycle products, supporting the idea that the clump originated near the He core of the progenitor. It has been recently found that Type IIb supernovae can result from the explosion of a blue supergiant with a thin hydrogen envelope, and our results support such a scenario for Cassiopeia A.

arXiv comment18 pages, 7 figures

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Cited by in corpus (9)

• The fully developed remnant of a neutrino-driven supernova: Evolution of ejecta structure and asymmetries in SNR Cassiopeia A
• A JWST Survey of the Supernova Remnant Cassiopeia A
• Evidence for past interaction with an asymmetric circumstellar shell in the young SNR Cassiopeia A
• A Sub-Solar Metallicity Progenitor for Cassiopeia A, the remnant of a Type IIb Supernova
• Sensitivity of ${}^{44}$Ti and ${}^{56}$Ni production in CCSN shock-driven nucleosynthesis to reaction rates
• X-ray diagnostics of Cassiopeia A's "Green Monster": evidence for dense shocked circumstellar plasma
• Kinematics of Supernova Remnants Using Multiepoch Maximum Likelihood Estimation: Chandra Observation of Cassiopeia A as an Example
• He abundance of Dense Circumstellar Clumps in the Cassiopeia A Supernova Remnant
• Near-Infrared Spectroscopy of Dense Ejecta Knots in the Outer Eastern Area of the Cassiopeia A Supernova Remnant