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Ejecta, Rings, and Dust in SN 1987A with JWST MIRI/MRS Published: 7/13/2023 2:36:00 PM Updated: 7/13/2023 2:36:00 PM

Paper abstract: Supernova (SN) 1987A is the nearest supernova in ~400 years. Using the{\em JWST} MIRI Medium Resolution Spectrograph, we spatially resolved theejecta, equatorial ring (ER) and outer rings in the mid-infrared 12,927 daysafter the explosion. The spectra are rich in line and dust continuum emission,both in the ejecta and the ring. Broad emission lines (280-380~km~s^{-1}FWHM) seen from all singly-ionized species originate from the expanding ER,with properties consistent with dense post-shock cooling gas. Narrower emissionlines (100-170~km~s^{-1} FWHM) are seen from species originating from a moreextended lower-density component whose high ionization may have been producedby shocks progressing through the ER, or by the UV radiation pulse associatedwith the original supernova event. The asymmetric east-west dust emission inthe ER has continued to fade, with constant temperature, signifying a reductionin dust mass. Small grains in the ER are preferentially destroyed, with largergrains from the progenitor surviving the transition from SN into SNR. The ER isfit with a single set of optical constants, eliminating the need for asecondary featureless hot dust component. We find several broad ejecta emissionlines from [Ne~{\sc ii}], [Ar~{\sc ii}], [Fe~{\sc ii}], and [Ni~{\sc ii}]. Withthe exception of [Fe~{\sc ii}]~25.99\mum, these all originate from the ejectaclose to the ring and are likely being excited by X-rays from the interaction.The [Fe~{\sc ii}]~5.34\mum to 25.99\mum line ratio indicates a temperatureof only a few hundred K in the inner core, consistent with being powered by{}^{44}Ti decay.