(2408.12462) Unveiling the physics of core-collapse supernovae with the Line Emission Mapper: observation of Cassiopeia A

(Submitted on August 22, 2024)

View a PDF of the article titled Unveiling the Physics of Core-Collapse Supernovae with the Line Emission Mapper: Observing Cassiopeia A, by S. Orlando and 14 other authors

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Abstract:Core-collapse supernova remnants (SNRs) exhibit complex morphologies and asymmetries, reflecting explosion anisotropies and early interactions with the circumstellar medium (CSM). Spectral analysis of these remnants can provide crucial insights into the dynamics of supernovae (SN) engines, the nature of progenitor stars, and the final stages of stellar evolution, including mass loss mechanisms in the pre-SN millennia.

This paper evaluates the potential of the Line Emission Mapper (LEM), an advanced X-ray probe concept proposed in response to NASA’s APEX 2023 call, to provide high-resolution spectra of SNRs. Such capabilities would enable detailed analysis of parent SNs and progenitor stars, currently beyond our capabilities. We used a hydrodynamic model that simulates the evolution of a neutrino-driven SN from core collapse to a mature 2000-year-old remnant. This model successfully reproduces the large-scale properties of Cassiopeia A at an age of about 350 years.

Using this model, we synthesized simulated LEM spectra of different regions of the SNR, taking into account factors such as line shifts and broadening due to plasma mass motion and ion thermal motion, deviations from ionization and temperature equilibrium, and absorption from the interstellar medium. Analysis of these simulated spectra with standard tools revealed impressive capabilities of the LEM. We demonstrated that fitting these spectra with plasma models accurately retrieves the line-of-sight velocity of the ejecta, allowing exploration of the 3D structure of shocked ejecta, similar to optical methods. The LEM also distinguishes between Doppler and thermal broadening of ion lines and measures ion temperatures near the edge of the SNR, providing information on ion heating at shock fronts and cooling in post-shock flows. This study highlights the potential of LEM to advance our understanding of core collapse SN dynamics and associated processes.