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We report the discovery of an eclipsing X-ray binary with a 3.62-hr periodwithin 24" of the center of the dwarf starburst galaxy NGC 4214. The orbitalperiod places interesting constraints on the nature of the binary, and allowsfor a few very different interpretations. The most likely possibility is thatthe source lies within NGC 4214 and has an X-ray luminosity of up to 7 e38ergs/s. In this case the binary may well be comprised of a naked He-burningdonor star with a neutron-star accretor, though a stellar-mass black-holeaccretor cannot be completely excluded. There is no obvious evidence for astrong stellar wind in the X-ray orbital light curve that would be expectedfrom a massive He star; thus, the mass of the He star should be <3-4 solarmasses. If correct, this would represent a new class of very luminous X-raybinary -- perhaps related to Cyg X-3. Other less likely possibilities include aconventional low-mass X-ray binary that somehow manages to produce such a highX-ray luminosity and is apparently persistent over an interval of years; or aforeground AM Her binary of much lower luminosity that fortuitously lies in thedirection of NGC 4214. Any model for this system must accommodate the lack ofan optical counterpart down to a limiting magnitude of 22.6 in the visible.Comment: 7 pages, ApJ accepted versio

Discovery of a 3.6 hr Eclipsing Luminous X‐Ray Binary in the Galaxy NGC 4214