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The variation in flux density obtained at 10522 MHz for Bursts 2, 3, and 4 is compared with that obtained by others at frequencies down to 365 MHz. The bursts appear to have a quasi-periodic modulation with a period of 3–4 h, which is different from the 4.8-h periodicity observed at X-ray and infrared wavelengths. The modulation is attributed to a fluctuation in the size of the expanding cloud of particles produced by either an instability in the atmosphere of Cygnus X-3 or by a built-in instability in the cloud itself.

La desactivation du catalyseur est due principalement a l'adsorption du propene sur deux sites et a la dimerisation de deux propenes sur des sites adjacents

It is shown that concentration-independent decay functions apply over a fairly wide range of poisoning mechanisms in which both products and reactants take some part in poisoning the active sites. The Time on Stream theory is therefore applicable to a wide range of decay mechanisms. In particular, it appears to be ideally suited to catalytic cracking, where the same intermediate carbonium ions are thought to lead to cracking as a main reaction or to poisoning as a side reaction. Our considerations of the chemistry of poisoning and simulation of catalyst decay behaviour lend credence to the earlier analyses of various kinetic parameters which have been obtained from experimental data using the Time on Stream theory. On a constate que les fonctions representant la perte d'activite d'un catalyseur, independantes de la concentration, s'appliquent a une assez grande variete de mecanismes d'empoisonnement, dans lesquels les produits et les reactifs participent d'une maniere ou d'une autre a l'empoisonnement des sites actifs. Par consequent, la theorie du temps en service s'applique a une variete de mecanismes de perte d'activite; elle semble convenir idealement au craquage catalytique, ou l'on pense que les měmes carbocations intermediaires conduisent au craquage, comme reaction principale, et a l'empoisonnement, comme reaction secondaire. En considerant la chimie de l'empoisonnement et la simulation du comportement de la perte d'activite du catalyseur nous avons pu confirmer les analyses de differents parametres cinetiques, obtenues anterieurement a partir de resultats experimentaux, en employant la theorie du temps en service.

The data for the event observed in Cyg X-3 early in September at many wavelengths indicate that the radio outburst originated in an expanding cloud of synchrotron emitting electrons. Details of the radiation mechanism and limits on models are discussed.

A giant radio outburst was observed from the X-ray source Cygnus X-3 on September 2, 1972. Flux density measurements were obtained at 10,522, 6,630 and 3,240 MHz as well as linear polarization measurements at 10,522 MHz. The evidence suggests a model of synchrotron radiation from an expanding cloud of relativistic particles. A computed upper limit for the source distance of ≤400 kpc implies that the source of the radio emission is galactic.

The calculated geometrical appearance of objects moving at relativistic speeds and subtending large angles at the observer is illustrated by diagrams of a plane grid and perspective views of a group of boxes. In addition to the distortion of scales in the direction of motion, planes perpendicular to the motion appear as hyperboloids. Contrary to an impression which might be taken from some papers on the subject, the Lorentz contraction is visible under suitable conditions, in particular for observations approximately at right angles to the motion.

The supernova remmant G109.2–1.0 was discovered at λ49cm by Hughes, Harten and van den Bergh (1981) during a survey of part of the Galactic plane. The northern part of it had been detected previously as the non-thermal radio source CTB109 by Wilson and Bolton (1960), and by Raghava Roa et al (1965), but the extended low brightness of the source and its close proximity to the very strong source Cas A, from which it is separated by ~5′, excluded it from any further detailed study. It was discovered independently at X-ray wavelengths by Gregory and Fahlman (1980). Recently, the original WSRT radio observations have been found to be in error as a result of applying the CLEAN procedure to an extended source, and since the object appears to contain an X-ray pulsar (Fahlman and Gregory, 1981), it was decided to carry out a more detailed and extensive mapping of the remmant using different antenna arrays and frequencies. This paper describes the results obtained at λ49cm and λ21cm using the Westerbork Synthesis Radio Telescope (WSRT), at λ21cm using the aperture synthesis array at the Dominion Radio Astrophysical Observatory (DRAO) and at λ4.6cm using the 46m telescope of the Algonquin Radio Observatory (ARO). Thus, data has been obtained from three completely independent telescopes, using completely independent data reduction systems.

In 1971, Chaisson and Ball (henceforth referred to as CB) reported detection of an anomalous recombination line in the low-frequency wings of He94α and He85α in W49A. The strength of the line was about 3% of the nearby hydrogen alpha line, and the velocity with respect to the local standard of rest (LSR) was 60-70 km s-1, assuming the emitting species is carbon.

The variation in flux density obtained at 10522 MHz for Bursts 2, 3, and 4 is compared with that obtained by others at frequencies down to 365 MHz. The bursts appear to have a quasi-periodic modulation with a period of 3–4 h, which is different from the 4.8-h periodicity observed at X-ray and infrared wavelengths. The modulation is attributed to a fluctuation in the size of the expanding cloud of particles produced by either an instability in the atmosphere of Cygnus X-3 or by a built-in instability in the cloud itself.

We have monitored the largest radio outburst to date from the binary $beta$ Per (Algol). The observations, made at frequencies of 1400, 2695, 6000, and 8085 MHz, mark the first time a non-X-ray radio binary has been observed at flux densities exceeding 1 Jy. The outburst probably consisted of two Algol-type flares. The radio spectrum remained essentially constant throughout the outburst, and no polarization was detected. (AIP)

The YZ Canis Minoris (Gliese 285), a late-type dwarf star with Balmer emission (dM4.5e), is a member of the UV Ceti class of flare stars. Obtaining good X-ray observations of a dMe star flare is important not only for understanding the physics of flares but also for testing current ideas regarding the similarity between stellar and solar flares. The Einstein X-ray Observatory has made it possible to conduct X-ray observations of dMe stars with unprecedented sensitivity. A description is presented of the results of a program of ground-based optical and radio observations of YZ CMi coordinated with those of the Einstein Observatory. The observations were carried out as part of a coordinated program on October 25, 26, and 27, 1979, when YZ CMi was on the dawn side of the earth. Comprehensive observational data were obtained of an event detected in all three wavelength regions on October 25, 1979.

An investigation has been carried out to detect newly formed early type stars by measuring the continuum radio emission from HII regions in R associations. Ten regions have been detected, attributed to stars in the spectral range 09.5V to B0.5V, and corresponds to a space density of 9 x 10/sup -5/ pc/sup -3/. This is about 1800 times greater than the value for the same type of star in the solar neighborhood. Arguments are presented to show that stars of early B spectral type are probably preferentially formed in R associations.

The absolute flux densities of Cyg A, Cas A, Tau A, and Vir A have been measured with an accuracy of about plus or minus 5% at 26.3 MHz using a method well suited for use at low radio frequencies where ionospheric scintillation is a limiting factor. No evidence for time variations in any of the four sources has been found.

The correlation between extragalactic X-ray sources and radio sources in a 26.3-MHz catalog is studied. A list of reliably identified sources is developed by examining X-ray, optical, and radio data for those candidate objects that are in or near the X-ray error boxes. The source 3UR 0432+05 is identified with 3C 120, 3UR 1555+27 (identified with A2142) is shown to be a steep-spectrum radio source, and it is found that 86% of the high-galactic-latitude sources can be reliably identified when the X-ray source error areas are no more than 1 sq deg. The results also indicate that: (1) X-ray sources identified with clusters of galaxies as a whole, with individual galaxies in clusters, and with separate isolated galaxies have similar decametric properties in that their spectral indices and radio luminosities fall in the same range; (2) there is a Bautz-Morgan dependence of both the X-ray and the decametric luminosities of clusters and of individual objects in clusters; and (3) the X-ray luminosity of all except compact sources appears to be approximately proportional to the decametric luminosity.

The differences in velocity of the various molecular lines from the region are summarized and explained in terms of the shock wave. In particular, this model can account for the production of OH and H/sub 2/O emissions at different velocities and different angular positions. To account for the comparatively large standoff position for the shock wave, it is suggested that the compact source may have a magnetic field of the order of 10/sup -3/ gauss, which is of the order of the magnetic field required to account for the interpretation of some features in the OH spectrum in terms of Zeeman splitting; a comparable value for the field is required to contain the H II region. (AIP)

Past determinations of the physical parameters of the Rosette nebula involving radio spectral line observations have generally employed the assumption of Local Thermodynamic Equilibrium (LTE). We present new recombination line and continuum observations made at 6.5 GHz with the 46-m dish at the Algonquin Radio Observatory, and perform a full non-LTE determination of the electron temperature, electron density and turbulent velocity in the H II region. The energetics and dynamics of the Rosette are reconsidered in the light of these new physical parameters.