T. Matilsky

Discovery of a 283-second periodic variation in the X-ray source 3U 0900-40

A 283 s periodic pulsation in the X-ray system 3U 0900--40 has been discovered during observations by the SAS-3 X-ray observatory. Pulse profiles of the 283 s periodicity are presented in five energy intervals covering the range 1--30 keV for the period 1975 July 19.4--23.9. The averaged profile is relatively simple at higher energies and is markedly more complex at lower energies. The peak 1--40 keV intensity observed for the source is 1.2 x 10/sup -8/ ergs cm/sup -2/ s/sup -1/, which corresponds to a luminosity of 2.1 x 10/sup 36/ ergs s/sup -1/ at a distance of 1.2 kpc. A search for soft X-ray emission (E<1 keV) yielded upper limits of 2 x 10/sup -11/ and 5 x 10/sup -11/ ergs cm/sup -2/ s/sup -1/ in the energy intervals 0.16--0.28 keV and 0.5--0.7 keV, respectively. (AIP)

A new transient source observed by Uhuru.

A strong X-ray source appeared sometime between March 25 and August 17, 1971. On August 23, its intensity, as observed by the Uhuru satellite, was about twice that of the Crab Nebula, corresponding to about 3 times 10 to the -8th power ergs per sq cm per sec, in the range 2-6 keV. On December 20, 1971, its intensity had declined to one-tenth of that value in the same energy range. Its spectrum was quite steep, and fit a power law with an average energy spectral index of 3.0. The variation of X-ray intensity over a 5-month period shows qualitative differences from the previously observed transient X-ray sources, Cen XR-2 and Cen XR-4.

Simultaneous ultraviolet, optical, and X-ray observations of the X-ray source Vela X-1 (HD 77581)

Ultraviolet spectra of HD 77581, associated with the binary X-ray source Vela X-1, taken with the International Ultraviolet Explorer satellite (IUE) show a spectrum typical of an early B-type supergiant. However, the P Cygni profiles of strong resonance lines show substantial variations with orbital phase. These variations can be ascribed to the changing ionization state in the stellar wind caused by the X-ray emitting companion as suggested by Hatchett and McCray. The mass loss of the supergiant primary is determined to be approx.1 x 10/sup -6/ M/sub sun/ yr/sup -1/. X-ray and spectroscopic and photometric optical observations, simultaneous with the IUE measurements, indicate behavior consistent with previous epochs. The interstellar spectrum shows strong, relatively broad lines of highly ionized Si IV and CIV which may result from the effects of X-rays upon the interstellar material neighboring the source.

Ultraviolet observations of AM Herculis with IUE

Ultraviolet observations of the binary X-ray source AM Herculis from the IUE satellite show strong emission lines of ions from O I to N V, probably originating in photoionized gas, and a continuum which is partially eclipsed in phase with the X-ray eclipse. The emission lines have broad (about 600 km/s) and sharp (about 80 km/s) components at different velocities, as has been seen in optical lines. The continuum is interpreted as two components, a blackbody (blackbody kT of 25-30 eV) which accounts for the X-ray emission below 0.5 keV and the eclipsed part of the UV continuum, and a component which is never eclipsed, whose spectrum is roughly proportional to the inverse of frequency. Strong ultraviolet emission due to optically thick cyclotron emission, which has been predicted theoretically, is not observed. This presents a severe difficulty for the theory of accretion onto the magnetic pole of a white dwarf.

Is hercules X-1 a strange attractor?

Des simulations numeriques elaborees a partir des observations du pulsars Hercules X-1 amenent a refuter la proposition de Hercules X-1 comme attracteur etrange etablie par Voges W., Atmanspacher H., et Scheingraber H. (1987, Ap. J., 320)

An X-ray study of the Centaurus Cluster of galaxies using Einstein

Einstein Imaging Proportional Counter observations of the core of the Centaurus Cluster of galaxies have been analyzed to map the 0.5-3.5 keV surface brightness and temperature of the intracluster gas. The emission is centered on NGC 4696, the elliptical galaxy believed to be at or near the dynamical center of the cluster. Because the X-ray-emitting gas responds to the gravitational potential of the cluster, the observations may be used to measure the total mass distribution around the central region. It is shown that the gas is very likely in hydrostatic equilibrium. It is found that surrounding NGC 4696, like M87 at the center of the Virgo Cluster, is a dark, massive halo, with a gravitating mass of about 2 x 10 to the 13th M out to a radius of about 20 arcmin (or 200 kpc for H(o) = 50 km/s Mpc). The elliptical galaxy NGC 4709, at the core of a more distant cluster, is also detected with a luminosity of 2 x 10 to the 40th ergs per sec. 47 references.

The transient periodic X-ray source in Taurus, A0535+26

Light curves of the 104 s periodicity in the transient X-ray source in Taurus (A0535+26) are presented for six energy intervals in the range 1-35 keV for the period 1975 May 30-June 2. The pulse structure ranges from an apparently simple modulation at higher energies to a very complex pattern at lower energies. No Doppler shift is observed in the 104 s pulse period during the three days of observations. This places severe constraints upon possible binary orbital motion. Upper limits on the power at other periodicities are approximately-less-than10 percent for 2 ms-2s and approximately-less-than2 percent for 2 s-2000 s. (AIP)

Radiative Lifetimes of Ultraviolet Transitions of Argon ii

The electron-excitation, phase-shift method of Lawrence has been applied to the determination of radiative lifetimes of Ar ii transitions. The measured levels, which are primarily those of 4p2S, 2P, 4D, were studied using transitions in the region from 1900–4500 A. The Ar ii lifetimes measured ranged from 1.2 to 10.6 nsec and involve a number of levels in which configuration interaction is present.

X-ray nova A0620-00 - Celestial position and low-energy flux

The X-ray nova A0620-00 (Nova Monocerotis 1975) has been observed with the SAS-3 satellite. The 1--10 keV intensity was observed to increase by a factor of 2.3 from August 8 to August 11. It reached and maintained a constant intensity of 1.7x10

The number-intensity distribution of X-ray sources observed by Uhuru.

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