Engineering topics

Hatchett, S.

Publications and source records attributed to Hatchett, S..

6 records

NASA NTRS1977

Evaporative winds in X-ray binaries

Evaporation of gas from the surface of HZ Her by Her X-1 and its implications regarding the mass transfer process are examined further. The powerful soft X-ray flux results in an evaporation rate greater than previous estimates. The evaporative flow is shown to be subsonic at first, with the result that the capture of evaporated gas by Her X-1 may be efficient, and the self-excited wind mechanism is possible. A criterion for stabilization of mass transfer by stellar wind mass loss is derived. Possible mechanisms for the long-period variability of HZ Her are discussed. Evaporative winds are also estimated for Sco X-1 and Cyg X-2 spectra.

Basko, M. M.↗

NASA NTRS1977

Structure of the iron fluorescence line in X-ray binaries

The paper presents an approximate solution to the iron K alpha line transfer problem in a stellar atmosphere illuminated by an external X-ray source as in a binary X-ray system. The emergent Comptonized line profile can independently yield information on the abundance of heavy elements in the primary atmosphere and on the solid angle subtended by the primary at the X-ray source.

Hatchett, S.↗

NASA NTRS1977

X-ray sources in stellar winds

A model of a binary X-ray source immersed in a stellar wind from its companion star is considered. The geometry of the constant ionization and temperature contours in the model is discussed, and X-ray radiative transfer through the wind is described. The results are applied to make predictions about the presence and variability of iron K-shell fluorescence lines, to explain the light curve of Cen X-3 during a 'low' to 'high' state transition in July 1972, and to predict variability with orbital phase of resonance ultraviolet lines such as N V at 1238 and 1242 A from the binary system.

Hatchett, S.↗

NASA NTRS1977

Interstellar ultraviolet absorption lines and galactic X-ray sources

X-ray photoionization can create zones of highly ionized trace elements in the interstellar gas around a galactic X-ray source. Ultraviolet absorption lines due to the resulting ionic column densities may be observable and may provide information on the environment and age of the X-ray source. The calculated column densities are sensitive to the rates of charge-exchange reactions.

Mccray, R.↗

NASA NTRS1976

Transfer of X-rays through a spherically symmetric gas cloud

Approximate solutions are presented for the transfer of radiation through spherically symmetric gas clouds surrounding a point source of X-rays. The approach is similar to that of Tarter and Salpeter (1969) except that heating by Compton scattering and the Auger effect is included. The temperature and ionization structure are sensitive to the source spectrum, and the solutions are not unique if soft X-rays are deficient. The emergent spectrum is rich in optical, ultraviolet, and X-ray emission lines. The radiation force due to photoelectric absorption of X-rays may exceed the force due to Compton scattering by a factor of order 10 for the radiation fields and densities likely to be encountered in galactic binary X-ray sources.

Hatchett, S.↗

NASA NTRS1975

Mass transfer in binary X-ray systems

The influence of X-ray heating on gas flows in binary X-ray systems is examined. A simple estimate is obtained for the evaporative wind flux from a stellar atmosphere due to X-ray heating which agrees with numerical calculations by Alme and Wilson (1974) but disagrees with calculations by Arons (1973) and by Basko and Sunyaev (1974) for the Her X-1/HZ Her system. The wind flux is sensitive to the soft X-ray spectrum. The self-excited wind mechanism does not work. Mass transfer in the Hercules system probably occurs by flow of the atmosphere of HZ Her through the gravitational saddle point of the system. The accretion gas stream is probably opaque with atomic density of not less than 10 to the 15th power per cu cm and is confined to a small fraction of 4(pi) steradians. Other binary X-ray systems are briefly discussed.

Mccray, R.↗