A Near‐Infrared and X‐Ray Study of W49 B: A Wind Cavity Explosion

We present near-infrared narrow-band images of the supernova remnant W49B,taken with the WIRC instrument on the Hale 200 inch telescope on Mt. Palomar.The 1.64 micron [Fe II] image reveals a barrel-shaped structure with coaxialrings, which is suggestive of bipolar wind structures surrounding massivestars. The 2.12 micron shocked molecular hydrogen image extends 1.9 pc outsideof the [Fe II] emission to the southeast. We also present archival Chandradata, which show an X-ray jet-like structure along the axis of the [Fe II]barrel, and flaring at each end. Fitting single temperature X-ray emissionmodels reveals: an enhancement of heavy elements, with particularly highabundances of hot Fe and Ni, and relatively metal-rich core and jet regions. Weinterpret these findings as evidence that W49B originated inside a wind-blownbubble (R ~ 5 pc) interior to a dense molecular cloud. This suggests thatW49B's progenitor was a supermassive star, that could significantly shape itssurrounding environment. We also suggest two interpretations for the jetmorphology, abundance variations and molecular hydrogen emission: (1) theexplosion may have been jet-driven and interacting with the molecular cavity(i.e. a Gamma-ray burst); or (2) the explosion could have been a traditionalsupernova, with the jet structure being the result of interactions between theshock and an enriched interstellar cloud.Comment: 9 pages with embedded figures Accepted by the Astrophysical Journa