NuSTAR Properties of G21.5-0.9
Abstract
Powered by a rapidly rotating and highly magnetized neutron star, pulsar wind nebulae (PWNe) are known to produce very high energy particles. However, the acceleration mechanism of particles to such high energies in PWNe is poorly understood. As a portion of these high energy particles emit synchrotron radiation in the X-ray band, studying such emissions provide clues in understand- ing the underlying acceleration mechanism. Hence, we present a comprehensive reanalysis of the archival NuSTAR X-ray spectra (3-45 keV) of PWN G21.5-0.9, incorporating an additional ∼190 ks of previously unused observations. We find that the difference in the calculated flux between data from the two detectors onboard NuSTAR (FPMA and FPMB) during the same observation exceed the expected ∼5% fluctuation and also find that the flux from FPMB is consistently higher across all observations. However, we still find a higher power-law photon index compared to the photon index in the soft X-ray band (0.5-8 keV) as measured by Chandra, indicating spectral softening in the X-ray band. Preliminary modelling using a one-zone model suggests that the spectral softening is not due to synchrotron cooling. We also find that the synchrotron emission from the highest energy particles peaks in the hard X-ray (NuSTAR) band. We will discuss the implications of these results for particle production and acceleration in G21.5-0.9.
- Publication:
-
Supernova Remnants: An Odyssey in Space after Stellar Death II
- Pub Date:
- June 2019
- Bibcode:
- 2019sros.confE.164H