X-ray, Optical and UV Observations of the Young Supernova Remnant in the Irregular Galaxy NGC 4449

A powerful young supernova remnant (SNR) similar to Cas A has recently been discovered in the irregular galaxy NGC 4449. We have obtained X-ray, optical and ultraviolet data which allow us to investigate possible models for this object and estimate its age. Several lines of argument indicate a massive star of order 25 M⊙ as the precursor to this remnant. If the x-ray emission is attributed to a reverse shock in the ejecta, the remnant should be ∼ 120 years old.