We are pleased to announce that the MACHO project will continue through calendar year 1998 on the 0.9m telescope. This team searches fields in the Galactic Center and the Magellanic Clouds, using a dedicated telescope in Australia (the Great Melbourne Reflector at MSSSO). The CTIO 0.9m is used 13% of the time by this project to provide accurate photometric measures for ongoing microlensing events.
The primary aim of the project is to test the hypothesis that a significant fraction of the dark matter in the halo of the Milky Way is made of objects like brown dwarfs or planets: these objects have come to be known as MACHOs, for Massive Compact Halo Objects. The signature of these objects is the occasional amplification of the light from extragalactic stars by the gravitational lens effect. The amplification can be large, but events are extremely rare. It is necessary to monitor photometrically several million stars for a period of years to obtain a useful detection rate. See the MACHO project home page at http://wwwmacho.mcmaster.ca for details, and Alcock et al ApJ, 479, 119, 1997 for some results. These surveys also provide extensive photometric catalogues for sources in the Magellanic Clouds and the Galaxy, particularly RR Lyrae and Cepheid variables. For example, see Alcock et al ApJ, 482, 89, 1997.
The observations are done by a dedicated observer each night, using a separate computer and their own calibrations. The Galactic Bulge is followed from March-October (approximately) and the Magellanic Clouds during the southern summer months. Observers granted 0.9-m time for their own programs can discuss the coordinating details with the mountain support personnel when they arrive on Tololo, or e-mail me (rschommer@noao.edu) in advance of their run. The MACHO project team members have been very cooperative and congenial colleagues. The resources they have provided have supported their special service observing requirements and also allowed some much needed upgrades to our small telescopes at CTIO.
Bob Schommer (rschommer@noao.edu)