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ABSTRACT THERE is a change in the X-ray spectral index of the Crab pulsar NP0532 near 10 keV (refs 1 and 2). We here examine this in a more quantitative fashion than before, using most of
the available published data, together with some unpublished data (Table 1). The pulsed fraction is the ratio of the pulsed radiation to total radiation; data published as the ratio of the
pulsed to unpulsed components have been duly corrected. The unpulsed reference level has been determined according to Ducros _et al._3 and where other workers have used a significantly
different convention, these data have been corrected. We believe that all data (31 points), can be validly compared. Other results, not considered here2,4,5, are generally in agreement with
the data we have used. The use of the pulsed fraction as the basic spectral quantity allows the low energy spectrum to be treated independently of interstellar absorption because it is the
same for both the pulsed and unpulsed components. Access through your institution Buy or subscribe This is a preview of subscription content, access via your institution ACCESS OPTIONS
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institutional subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS DISCOVERY OF A RADIATION COMPONENT FROM THE VELA PULSAR REACHING 20
TERAELECTRONVOLTS Article 05 October 2023 SIMULTANEOUS SPACE AND PHASE RESOLVED X-RAY POLARIMETRY OF THE CRAB PULSAR AND NEBULA Article 06 April 2023 SPECTRAL INDEX-FLUX RELATION FOR
INVESTIGATING THE ORIGINS OF STEEP DECAY IN _Γ_-RAY BURSTS Article Open access 07 July 2021 REFERENCES * Fritz, G., Meekins, J. F., Chubb, T. A., and Friedman, H., _Astrophys. J. Lett._,
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AND AFFILIATIONS * Department of Physics, University of Tasmania, Box 252C, Hobart, Tasmania, Australia R. M. THOMAS * Service d'Electronique Physique, CEN Saclay, BP No. 2, 91190,
Gif-sur- Yvette, France R. ROTHENFLUG Authors * R. M. THOMAS View author publications You can also search for this author inPubMed Google Scholar * R. ROTHENFLUG View author publications You
can also search for this author inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE THOMAS, R., ROTHENFLUG, R. X-ray spectrum of
NP0532. _Nature_ 249, 812–814 (1974). https://doi.org/10.1038/249812a0 Download citation * Received: 04 March 1974 * Revised: 02 April 1974 * Issue Date: 28 June 1974 * DOI:
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