SPATIALLY RESOLVED SPECTROSCOPY OF A PULSAR WIND NEBULA IN MSH 15–56

Abstract

We report the study of a pulsar wind nebula (PWN) in the middle-aged supernova remnant (SNR) MSH 15–56. High-resolution X-ray imaging observations using XMM-Newton and Chandra provided clear images of its comet-like structure, as seen in other PWNe moving rapidly through interstellar mediums. At the PWN apex, Chandra detected a point source emitting a power-law spectrum with a photon index of Γ = 1.3. The photon index of the PWN steepens from 1.7 to 2.5 along the flow line from the apex toward the tail, implying that the PWN is powered by the point source. The opening angle of the tail implies a pulsar velocity of v PSR = 1900 km s–1. We also discovered a thin X-ray filament at the edge of the SNR and just near the PWN. Assuming that the SNR is in the Sedov phase, the shell is expanding at 860 km s–1, which is consistent with the existence of the non-thermal filament. Based on the physical relationship, the PWN will run through the blast wave in the near future.