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Arxiv: Investigating the Electron Capture Supernova Candidate AT 2019abn with JWST Spectroscopy Published: 7/30/2024 12:41:25 AM Updated: 7/30/2024 12:41:25 AM
Paper abstract: The James Webb Space Telescope (JWST) has opened up a new window to studyhighly reddened explosive transients. We present results from late-time (1421days post-explosion) JWST follow-up spectroscopic observations with NIRSpec andMIRI LRS of the intermediate luminosity red transient (ILRT) AT 2019abn locatedin the nearby Messier 51 galaxy (8.6 Mpc). ILRTs represent a mysterious classof transients which exhibit peak luminosities between those of classical novaeand supernovae and which are known to be highly dust obscured. Similar to theprototypical examples of this class of objects, NGC 300 2008-OT and SN 2008S,AT 2019abn has an extremely red and dusty progenitor detected only inpre-explosion Spitzer/IRAC imaging at 3.6 and 4.5 micron and not in deepoptical or near-infrared HST images. We find that late time observations of AT2019abn from NEOWISE and JWST are consistent with the late time evolution of SN2008S. In part because they are so obscured by dust, it is unknown whatproduces an ILRT with hypotheses ranging from high mass stellar merger events,non-terminal stellar outbursts, or terminal supernovae explosions throughelectron-capture in super-AGB stars. Our JWST observations show strong mid-IRClass C PAH features at 6.3 and 8.25 micron typical of carbon-rich post-AGBsources. These features suggest the dust around AT 2019abn, either pre-existingor newly formed in the ejecta, is composed of carbonaceous grains which are nottypically observed around red supergiants. However, depending on the strengthand temperature of hot bottom burning, SAGBs may be expected to exhibit acarbon-rich chemistry. Thus our JWST observations are consistent with AT2019abn having an SAGB progenitor.