Philip Yock
, PASA, 17 (1), 35.
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Title/Abstract Page: Observations from Australasia using
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Introduction
The new technique of gravitational microlensing has developed rapidly since its introduction to astronomy in 1993. During that year the MACHO group in Australia, and the EROS and OGLE groups in Chile, made the first observations (Alcock et al. 1993; Aubourg et al. 1993; Udalski et al. 1993). These were quickly followed by observations by the DUO group (Alard et al. 1995). All these groups observed the apparent brightening of a distant star caused by the lens-like effect of a closer, collinear star, as had been predicted by Einstein (1936). The brightening was found to follow the characteristic achromatic light curve calculated by Paczynski (1986) as the stars moved into, and out of, collinearity. Paczynski had proposed using the technique to search for brown dwarfs in the dark halo of the Galaxy through their lensing effect on stars in the Magellanic Clouds. Subsequently, other uses for the technique were proposed, including studies of galactic structure, stellar spectra, stellar atmospheres and extra-solar planets. Other groups were formed to exploit these applications, some with telescopes in Australasia. In this paper, the main observations that have been carried out from Australasia to date are described. A proposal to include Antarctica as an observing site in the future is also described. For the most part the content follows an invited talk given by the author to the Joint Meeting of the Astronomical Society of Australia and the Royal Astronomical Society of New Zealand that was held at Sydney in July 1999. The observations from Australasia have been made by groups known as MACHO, GMAN, PLANET, MPS, and MOA. All the fields mentioned above have been studied, viz. dark matter, galactic structure, stellar spectra, stellar atmospheres and extra-solar planets. These are dealt with in turn in the paper. Most of the groups mentioned above maintain web sites on their work. These are at:MACHO: http://wwwmacho.mcmaster.ca/
PLANET: http://thales.astro.rug.nl/
planet/ MOA: http://www.phys.vuw.ac.nz/dept/projects/moa/
MPS: http://bustard.phys.nd.edu/MPS/
EROS: http://www.lal.in2p3.fr/recherche/eros
OGLE: http://www.astrouw.edu.pl/
ftp/ogle/index.html. The last two groups, EROS and OGLE, are the Chilean based ones. The field of gravitational lensing as a whole, including its history dating back to 1804, was comprehensively reviewed recently by Wambsganss at http://www.livingreviews.org/Articles/Volume1/1998-12wamb/index.html.
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Title/Abstract Page: Observations from Australasia using
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