Variable Unidentified Emission near 6307 Å in η Carinae

We have discovered a conspicuous unidentified variable feature near 6307 Å in the spectrum of η Carinae that is spatially unresolved from the central star and its wind (r≲200–300 AU). It is significant for two reasons: first, such prominent unidentified lines are now rare in this object, and second, this feature varies strongly and systematically. It exhibits a combination of characteristics that, so far as we know, are unique in η Carinae’s spectrum. It may provide insights into the recurrent spectroscopic events and the star’s long‐term brightening.