Third-epoch proper motions in the outer shell of ETA Carinae

Abstract

Proper motions have been measured for several of the nitrogen-rich expanding knots in the outer shell of η Car from third-epoch, CTIO 4-m plate material which extends the previous quarter-century baseline by an additional decade. Some possible evidence for decelerations is found, implying significant revisions in the correspondences between particular features and the historical light curve, with respect to the assumption of uniform motions. Extension of the baseline into the next century or observations from space will enable a distinction between the two possibilities.