Galactic Radiation at Radio Frequencies. VI. Low Altitude Scintillations of the Discrete Sources

Bolton, J. G.; Slee, O. B.; Stanley, G. J.

doi:10.1071/ph530434

Cited by 43 publications

(16 citation statements)

References 2 publications

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“…Such a variation was found by Hewish (1952) and also by Bolton, Slee, and Stanley (1953) for frequencies near 100 Mc/s. However, it will be seen from Figure 10 (b) that the scintillation index for the smallest (angular size) sources observed at 18·3 Mc/s is not much more than the index for s.ourpes observed at 81 Mc/s by Ryle and Hewish (1950), indicating a very slow variation with wavelength.…”

Section: Lu -1·!!5supporting

confidence: 65%

“…However, Ryle and Hewish (1950) have found a diurnal variation in the amplitude of these " scintillations" of sources observed at high angles while Bolton, Slee, and Stanley (1953) found both annual and diurnal variations for their low angle observations and it was therefore' necessary to check whether the lack of scintillations for some sources was not merely an effect of the times of observation. Unfortunately ,there are no sources for which observations extend over mote than a few months (corresponding to a few hours' variation in local time of observation), but a number of sources were chosen for study of their scintillations so that there were observations covering an hours of the day and a large part of the year.…”

Section: (C) Distribution Of the Discrete Sourcesmentioning

confidence: 99%

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Observations of the General Background and Discrete Sources of 18·3 Mc/s Cosmic Noise

Shain¹,

Higgins²

1954

Aust. J. Phys.

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SummaryA survey of a broad strip of the sky, centred on Dec. -32°, has been made at a frequency of 18·3 Mcls using an aerial with an overall beam width to half-power of 17°. Previous results concerning the background distribution of brightness have been confirmed and 37 discrete sources have been detected. The distribution of these sources shows some galactic concentration; it becomes homogeneous if sources within 18° of the galactic plane are excluded. From observations of source scintillations, it is concluded that some of the discrete sources have angular sizes of the order of 1°. No correlation was found between the occurrence of scintillations and published ionospheric data, but the observations are consistent with an origin of the scintillations in irregularities, of dimensions about 4 km, at a height of about 500 km.I. INTRODUOTION A previous paper (Shain 1951) described observations of 18·3 Mc/s cosmic noise which were made using an aerial with the direction of maximum sensitivity fixed vertically upwards in latitude 34 oS. The aerial thus received cosmic noise averaged over a rather wide strip of the sky centred on Dec. -34°. It was shown, by comparison with the resUlts of Bolton and Westfold (1950), that the observed variations in intensity as the aerial scanned this strip (which included the centre and the south pole of the Galaxy) could be explained if contours of equal intensity at 18·3 Mc/s were of the same shape as at 100 Mc/s, the absolute intensity being much higher, and if, also, the ratio of the intensity at 18·3 Mc/s to the intensity at 100 Mc/s near the galactic centre were somewhat lower than the corresponding ratio away from the centre. Although these observations gave some indication of the way in which the . intensity of cosmic noise at 18·3 Mc/s would vary over the sky, it was apparent that a detailed survey should be made with an aerial of smaller beam width, at least over the important regions near the galactic centre and at some distance from the centre. Accordingly, an aerial was constructed, to operate at 18·3 Mc/s, with a beam width of 17° between half-power points, and for which the main lobe could be swung at least 20° north and south of the zenith.The present paper describes the observations of cosmic noise made with this aerial, these observations being mainly concentrated in the range of declination from -12 to _52°. The intensities observed were of the same order as those previously reported. With the former aerial system it was thought that the effects of one or two discrete sources of-radiation could be detected; with the * Division of Radiophysics, O.S.I.R.O., University Grounds, Sydney.

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Section: Lu -1·!!5supporting

confidence: 65%

Section: (C) Distribution Of the Discrete Sourcesmentioning

confidence: 99%

Observations of the General Background and Discrete Sources of 18·3 Mc/s Cosmic Noise

Shain¹,

Higgins²

1954

Aust. J. Phys.

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“…With the benefit of improved electronics and a beamwidth of just 12 • , this survey produced 104 sources. Bolton, Stanley and Slee, in various authorship combinations, then prepared three different papers on aspects of this survey, but often incorporating data from the earlier Dover Heights source surveys (see Bolton, Stanley and Slee, 1953;and Bolton, Westfold, Stanley and Slee, 1954). Slee also made a special study of the intensity variations exhibited by the Hydra A source, and this was written up as his first solo paper (Slee, 1955;c.f.…”

Section: Investigating the Enigmatic 'Radio Stars'mentioning

confidence: 99%

From the Solar Corona to Clusters of Galaxies: The Radio Astronomy of Bruce Slee

Orchiston¹

2004

Publ. – Astron. Soc. Aust

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Owen Bruce Slee is one of the pioneers of Australian radio astronomy. During World War II he independently discovered solar radio emission, and, after joining the CSIRO Division of Radiophysics, used a succession of increasingly more sophisticated radio telescopes to examine an amazing variety of celestial objects and phenomena. These ranged from the solar corona and other targets in our solar system, to different types of stars and the ISM in our Galaxy, and beyond to distant galaxies and clusters of galaxies. Although long retired, Slee continues to carry out research, with emphasis on active stars and clusters of galaxies. A quiet and unassuming man, Slee has spent more than half a century making an important, wide-ranging contribution to astronomy, and his work deserves to be more widely known.

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“…However, very few Cases of general absorption of the radiation at frequencies of the order of 100 Mcts are known. Bolton, Slee, and Stanley (1953) reported that on three occasions out of about 1000 observations of the Oygnus source at rising, marked general absorption for periods up to 1 hr were noticed, but on these occasions fast and intense scintillations were 'also present. Since the flux density variations of Hydra-A show no correlation with scintillation activity, it is very unlikely that they are produced by the same mechanisms.…”

Section: Sidereal Time (Hr)mentioning

confidence: 98%

Apparent Intensity Variations of the Radio Source Hydra?A

Slee¹

1955

Aust. J. Phys.

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SummaryThis paper describes the results of a detailed study of the flux density of the discrete radio source, Hydra-A. Over a period of 12 months, approximately 200 measurements of the Hydra-A intensity were compared with a similar number of observations on other strong sources. It was concluded that the observed flux density of Hydra-A is much more variable than that of these other sources, although no periodic changes have yet been detected. Possible mechanisms for the observed intensity changes are discussed.

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Galactic Radiation at Radio Frequencies. VI. Low Altitude Scintillations of the Discrete Sources

Cited by 43 publications

References 2 publications

Observations of the General Background and Discrete Sources of 18·3 Mc/s Cosmic Noise

Observations of the General Background and Discrete Sources of 18·3 Mc/s Cosmic Noise

From the Solar Corona to Clusters of Galaxies: The Radio Astronomy of Bruce Slee

Apparent Intensity Variations of the Radio Source Hydra?A

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