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Arxiv: The Sunburst Arc with JWST: II. Observations of an Eta Carinae Analog at z=2.37 Published: 5/11/2024 11:25:10 AM Updated: 5/11/2024 11:25:10 AM

Paper abstract: "Godzilla" is a peculiar object within the gravitationally lensed SunburstArc at z=2.37. Despite being very bright, it appears in only one of thetwelve lensed images of the source galaxy, and shows exotic spectroscopicproperties not found elsewhere in the galaxy. We use JWST's unique combinationof spatial resolution and spectroscopic sensitivity to provide a unified,coherent explanation of the physical nature of Godzilla. We measure fluxes andkinematic properties of rest-optical emission lines in Godzilla and surroundingregions. Using standard line ratio-based diagnostic methods in combination withNIRCam imaging and ground based rest-UV spectra, we characterize Godzilla andits surroundings. We find that Godzilla is most likely an extremely magnified,non-erupting LBV star with dense gas condensations in close proximity. Amongaround 60 detected lines, we find a cascade of strong O I lines pumped byintense Ly\beta emission, as well as Ly\alpha-pumped rest-optical Fe IIlines, reminiscent of the Weigelt blobs in the local LBV star Eta Carinae.Godzilla is surrounded by dusty, inhomogeneous gas common to massive, evolvedstars. Spectra and images of Godzilla and adjacent objects and the detection ofa low-surface brightness foreground galaxy in the NIRCam data support theinterpretation that Godzilla is a stellar-scale object extremely magnified byalignment with lensing caustics. To explain the dusty surroundings, strong [NeIII] and line kinematics simultaneously, we argue that Godzilla is apost-eruption LBV accompanied by a hotter companion and/or gas condensationsexposed to more intense radiation compared to the Weigelt blobs. We expectperiodic spectroscopic variations if Godzilla is a binary system. If Godzillais confirmed to be an LBV star, it expands the distance to the furthest knownLBV from a dozen Mpc to several Gpc.