A1 Refereed original research article in a scientific journal
Characterization of the Optical and X-ray Properties of the Northwestern Wisps in the Crab Nebula
Authors: T Schweizer, N Bucciantini, W Idec, K Nilsson, A Tennant, M C Weisskopf, R Zanin
Publisher: OXFORD UNIV PRESS
Publication year: 2013
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Number in series: 4
Volume: 433
Issue: 4
First page : 3325
Last page: 3335
Number of pages: 11
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stt995
Abstract
We have studied the wisps to the north-west of the Crab pulsar as part of a multiwavelength campaign in the visible and in X-rays. Optical observations were obtained using the Nordic Optical Telescope in La Palma and X-ray observations were made with the Chandra X-ray Observatory. The observing campaign took place from 2010 October until 2012 September. About once per year we observe wisps forming and peeling off from (or near) the region commonly associated with the termination shock of the pulsar wind. We find that the exact locations of the north-western wisps in the optical and in X-rays are similar but not coincident, with X-ray wisps preferentially located closer to the pulsar. This suggests that the optical and X-ray wisps are not produced by the same particle distribution. Our measurements and their implications are interpreted in terms of a Doppler-boosted ring model that has its origin in magnetohydrodynamic (MHD) modelling. While the Doppler boosting factors inferred from the X-ray wisps are consistent with current MHD simulations of pulsar wind nebulae, the optical boosting factors are not, and typically exceed values from MHD simulations by about a factor of 3.
We have studied the wisps to the north-west of the Crab pulsar as part of a multiwavelength campaign in the visible and in X-rays. Optical observations were obtained using the Nordic Optical Telescope in La Palma and X-ray observations were made with the Chandra X-ray Observatory. The observing campaign took place from 2010 October until 2012 September. About once per year we observe wisps forming and peeling off from (or near) the region commonly associated with the termination shock of the pulsar wind. We find that the exact locations of the north-western wisps in the optical and in X-rays are similar but not coincident, with X-ray wisps preferentially located closer to the pulsar. This suggests that the optical and X-ray wisps are not produced by the same particle distribution. Our measurements and their implications are interpreted in terms of a Doppler-boosted ring model that has its origin in magnetohydrodynamic (MHD) modelling. While the Doppler boosting factors inferred from the X-ray wisps are consistent with current MHD simulations of pulsar wind nebulae, the optical boosting factors are not, and typically exceed values from MHD simulations by about a factor of 3.
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