Mullard Space Science Laboratory

A. N. Parmar
Studies of X-ray emission from Hercules X-1 OAO1653-40 and X-ray spectroscopy of solar flares

1981 (supervisor: P. W. Sanford)

In the introduction to this thesis reviews of the early history of X-ray astronomy, X-ray binaries and the processes responsible for X-radiation from astronomical objects are presented.

Previous optical observations of Hercules X-1 are discussed along with models for the 35 day modulation in X-ray intensity. Results of X-ray observations made in February 1977 with the Ariel V satellite are presented and their significance discussed. A new pulse period determination is made and a light curve for part of the secondary on-state emission presented.

Observations using the Copernicus satellite which suggested that the massive binary system V861 Sco contains a black hole are reviewed. More recent HEAO-1 and the Einstein results presented in this thesis suggest that V861 Sco is not a significant X-ray source and that the system probably does not contain a black hole.

Observations of the 38 sec pulsar OAO1653-40 with the Einstein Observatory are discussed and a precise (to 1 arc minute) position for the source presented. The first measurement of the spin-up rate of this pulsar is given and the search for the optical counterpart discussed.

A description of the capabilities and method of construction of the Bent Crystal Spectrometer (BCS) on the Solar Maximum Mission satellite is made. The subtraction of an instrumentally induced background is discussed and the corrections to the dispersions and effective areas that need to be made due to the non-uniform crystal curvatures are indicated.

Finally, a review of the theory of the spectrum of Hydrogen-like Iron (Fe XXVI) near 1.7 Angstroms is made and the first well resolved spectra of Fe XXVI obtained from solar flares presented. The Fe XXVI lines in these spectra are identified and electron temperatures and emission measures derived. A comparision with results obtained from lower temperature Fe XXV and Ca XIX BCS measurements is also made.


Mullard Space Science Laboratory - Holmbury St Mary - Dorking - Surrey - RH5 6NTTelephone: +44 (0) 1483 204100 - Copyright © 1999-2005 UCL

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