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Soft X-Rays from the Cygnus Loop


Stevens, John Charles (1973) Soft X-Rays from the Cygnus Loop. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/DPCX-XK67.


A detailed soft x-ray survey of the Cygnus Loop, obtained from a rocket-borne experiment, provides evidence that the x-ray emission from this supernova remnant is produced by the interaction of a shock wave and the interstellar medium. A spatial map, having 0.5° by 0.5° resolution, of the structure of the Cygnus Loop in 0.2 to 1.5 kev x-rays is presented. The map shows regions of x-ray emission which correlate well with features at radio and optical wavelengths. It also shows regions for which the antithesis holds. A detailed spectral examination of the total emission from the Loop by a proportional counter equipped with a two-element filter system, shows evidence for line emission between 530 and 690 ev. The overall spectrum is found to be well represented by a thermal bremsstrahlung spectrum with line emission. The intensity of x-ray emission between 0.2 and 1.5 kev from the Cygnus Loop is found to be 1.2 ± 0.3 x 10-8 ergs/cm2-sec at the earth. Assuming a distance of 770 pc to the Loop and a columnar density of inter- stellar hydrogen of .48 ± .02 x 1021 atoms/cm2 the total energy radiated in 0.2 to 1.5 kev x-rays by the Loop is found to be 2.1 x 1036 ergs/sec. An inhomogeneous anisotropic shock wave model of the Cygnus Loop is found to be required by the data. Such a model is developed and is shown to explain the spatial and spectral appearances of the Cygnus Loop in soft x-rays. The model requires a shock front expansion velocity only as large as that implied by the optical radial velocity measurements.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Garmire, Gordon Paul
Thesis Committee:
  • Unknown, Unknown
Defense Date:12 September 1972
Funding AgencyGrant Number
Record Number:CaltechTHESIS:07182018-102049405
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11124
Deposited On:23 Jul 2018 17:04
Last Modified:21 Dec 2019 04:00

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