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Arxiv: A Low Metallicity Massive Contact Binary Star System Candidate in WLM identified by Hubble and James Webb Space Telescope imaging Published: 10/21/2024 9:07:10 PM Updated: 10/21/2024 9:07:10 PM

Paper abstract: We present archival HST and JWST ultraviolet through near infrared timeseries photometric observations of a massive minimal-contact binary candidatein the metal-poor galaxy WLM (Z = 0.14 Z_{\odot}). This discovery marks thelowest metallicity contact binary candidate observed to date. We determine thenature of the two stars in the binary by using the eclipsing binary modelingsoftware (PHysics Of Eclipsing BinariEs; PHOEBE) to train a neural network tofit our observed panchromatic multi-epoch photometry. The best fit modelconsists of two hot MS stars (T_1=29800^{+2300}_{-1700} K,M_1=16^{+2}_{-3}~M_{\odot}, and T_2=18000^{+5000}_{-5000} K,M_2=7^{+5}_{-3}~M_{\odot}). We discuss plausible evolutionary paths for thesystem, and suggest the system is likely to be currently in a contact phasebefore ultimately ending in a merger. Future spectroscopy will help to furthernarrow down evolutionary pathways. This work showcases a novel use of data ofJWST and HST imaging originally taken to characterize RR Lyrae. We expect timeseries imaging from LSST, BlackGEM, etc. to uncover similar types of objects innearby galaxies.