A. E. Vaughan

A Search for Transient Events at 843 MHz

The Molonglo Observatory Synthesis Telescope is equipped with a transient event monitoring system which operates during normal synthesis observations. The device is designed to respond to impulsive signals which occur within the passband (843.0 ± 1.5 MHz) with time scales between 0.001 ms and 800 ms. The multiple beam facility of the telescope provides some discrimination against local interference. An upper limit of 1.7 × 10 −2 events s −1 sr −1 has been placed on celestial events with durations between 1 ms and 25 ms and energy density ≥ 10 −28 J m −2 Hz −1 . The monitoring system has been recently reconfigured to improve the recognition and rejection of impulsive signals of non-celestial origin.

The Parkes-MIT-NRAO Southern Sky Survey at 4850 MHz

G. Behrens, C. Chestnut, National Radio Astronomy Observatory, Greenbank, USA B. F. Burke, A. Fletcher, Massachusetts Institute of Technology, Cambridge, USA K. S. Russell, A. Savage, UK Schmidt Telescope, Anglo-Australian Observatory, Coonabarabran NSW 2357 J . L im, A. E. Vaughan, School of Mathematics and Physics, Macquarie University, North Ryde NSW 2113 S. Cote, Mount Stromlo and Siding Spring Observatories, Private Bag Weston ACT 2611 M. Anderson, A. Hons, G. L. White, Faculty of Science and Technology, University of Western Sydney, Kingswood NSW 2747 S. Amy, A. Burgess, S. Chan, L. Cram, A. Gray, W . Walsh, D. Campbell-Wilson, Astrophysics Department, University of Sydney, NSW 2006 V. Mclntyre, P. Randall, M. Suters, W. J. Zealey, Department of Physics, University of Wollongong, Wollongong NSW 2500

Positions of Four Pulsars

ACCURATE positions of four pulsars1 have been measured with the one mile cross type radio telescope at the Molonglo Radio Observatory. This instrument2, which operates at a frequency of 408 MHz, forms eleven beams simultaneously, each 2.7′ in right ascension by 2.8′ in declination and separated by 1.4′ in the north–south direction. Simultaneously with this the east–west arm can be used alone, giving a fan beam in the meridian plane 2.0′ by 4.2°. Similarly, there are eleven simultaneous fan beams available from the north–south arm; these are elongated in the east–west direction. Results from all these systems have been combined here. CP 1919 is, however, right on the northern limit of the east–west system.

843 MHz Emission from the Active Star AB Dor

The Molonglo Observatory synthesis telescope has been used to obtain twelve observations of a 23′ arc field containing the active star AB Dor. On each occasion, an unresolved source close to the optical position of AB Dor was observed. The source exhibits day-to-day variations of flux density, with a mean value of ∼4 mJy. The identification of the source with the star and the variations in emission are discussed.

A Dedicated Variable Star Observatory

A small astronomical observatory has been constructed on the edge of the Macquarie University campus at North Ryde in Sydney. It will be used primarily for photoelectric observations of variable stars. Further improvements to the present observing system are being planned and observations have already started on β Cepheids.