Ethan Joshua Schreier

ANS observations of Cygnus X-1

Cygnus X-1 was observed from 3 November until 9 November, 1974, using the hard X-ray (1–28 keV) and soft X-ray (1–8 keV) experiment on board the Astronomical Netherlands Satellite. On three occasions, on 4 and 5 November, the X-ray spectrum was observed to be harder, while the flux intensity in the 1–7 keV ranges decreased by ∼50% from its quiescent value. These events occurred near and following the time of superior conjunction of the likely optical counterpart HDE 226 868. These events appear to be the same as previously reported absorption dips and reveal this phenomenon to be more complex than had been believed. A systematic study of the X-ray spectral variations in these energy bands, on a time scale of 64 seconds over the period of the spectroscopic binary, is presented.

TIMING EFFECTS IN ROTATING NEUTRON STARS

I n this talk, 1 will be discussing observations of rotating neutron stars, and in particular, what we can learn about neutron stars from studying various timing effects. I intend to concentrate on the observations and their immediate interpretations; other papers will be concerned with more of the theory. In the spirit of this session, 1 will try not to deal with observations which are primarily concerned with binary companions, third body effects, general relativistic orbit corrections, or anything else which doesn’t directly concern neutron star structure, except where these effects offer alternative explanations. Furthermore, the topic of neutron star masses and particularly limiting masses will be dealt with in the following paper. I n reviewing the radio pulsar literature of the last two or three years, I find little new observational data which directly bear on neutron star structure. The binary pulsar is much more exciting for its implications about mass, evolution, and relativistic effects. However, certain x-ray pulsar data have recently been interpreted in terms of the response of the star to accretion torques with direct application to determinations of magnetic fields and possibly moments of inertia. I will thus concentrate on these data, drawing parallels with the radio pulsars as appropriate.

The Galactic X-Ray Sources

When X-ray sources in the galaxy were discovered in 1962 (Giacconi et al., 1962) it was only possible to speculate on their nature, which centered on supernova and cosmic- ray phenomena since these were the only very energetic events known. In particular, the discovery of an X-ray source associated with the Crab Nebula led to the idea that the emission might be the thermal radiation from the surface of a hot, neutron star, However, it was soon demonstrated (Bowyer et al., 1964) that a neutron star could not be responsible for the bulk of the X-radiation from the Crab, and it was not possible to exclude highly pathological conditions in otherwise ordinary stellar systems as being responsible for the X-ray sources (c.f., Hayakawa and Matsuoka, 1964).

Spectral and intensity variations in cygnus X-3 by the Astronomical Netherlands Satellite

Measurements obtained with the Utrecht (1–8 keV) and Cambridge (1–28 keV) instruments on board the Astronomical Netherlands Satellite are discussed. Particularly, the 4.8 hr period is investigated.