Morgan, E. H. | Engineering Papers

NASA NTRS1990

The X-ray Timing Explorer

The capabilities of the X-ray Timing Explorer (XTE) are described with particular attention paid to current scientific problems it will address from galactic neutron star systems to active galactic nuclei. It features a low-background continuous 2-200 keV response with large apertures (a 0.63 sq m proportional counter array and a 0.16 sq m dual rocking NaI/CsI scintillation array). Rapid response (in hours) to temporal phenomena, e.g. transients, is obtained by virtue of a scanning all-sky monitor and rapid maneuverability. XTE will carry out detailed energy-resolved studies of phenomena close to neutron stars (e.g. QPO's) because of its submillisecond timing, its high telemetry rates, and the high throughput of its data system.

Bradt, H. V.↗

NASA NTRS1982

Circinus X-1 - X-ray observations with SAS 3

Eight observations of Cir X-1 with SAS 3, each lasting 1-6 days, have yielded a variety of new phenomena, viz., a luminous state of steady emission, rapid large-intensity dips, an extremely rapid X-ray transition, and bright flares. Through searches for periodic X-ray pulsations were carried out on data trains of duration up to 6 days; upper limits for pulsations with periods greater than 250 microsec range down to 0.3%. Aperiodic variability with characteristic times of 0.4-1.0 sec was observed but is not well characterized by a simple shot noise model. No millisecond bursts were observed during 40,000 sec in three separate observations. Spectral parameters derived before and after several X-ray transitions indicate that the transitions are not due to absorption of X-rays by intervening gas. Models previously proposed for the Cir X-1 system do not easily provide explanations for all the complex phenomena reported herein.

Dower, R. G.↗