Perth Automatic Supernova Search

This search has been conducted over the last three years by Andrew Williams and Ralph Martin. The 61 cm telescope is now fully automated, although an observer has to be present to start up and to watch the weather. The magnitude limit during the search was 16.5 - 17.0 (Williams 1996). The figures cover a three-year period starting early in 1993. Figures for either eighteen-month period are not known, although more work was done in the second half than in the first. Each observation normally took four minutes, thus averaging fifteen galaxy observations per hour. A total of 5530 observations were made. The galaxies searched were 300 specially chosen large spiral galaxies in which a higher supernova rate was expected. Originally, there was an expectation that the search would use up to 50% of available observing time but in practice many other programs were also catered for. These observations yielded five confirmed supernova discoveries, although the Perth observers believed! they found a sixth supernova which could not be confirmed independently before the galaxy disappeared behind the sun. No other supernovae were seen.

It should be noted that the number of supernovae seen is the true gauge of the effectiveness of a search, in relation to the number of galaxies searched, and not the number of discoveries. The number of these supernovae which are discovered by any group depends upon what competition there is for discoveries at the time, and this may vary from week to week. It has been questioned whether automatic and visual searches can be compared in this way since the automatic searches have a fixed list of targets, while visual observers are likely to be biased in observing a galaxy with a known supernova. In fact, the target list of galaxies for the visual search is also well defined, and I have only included galaxies with known supernovae which were on the target list and so would reasonably be expected to be discovered. In each case, it was clear whether the galaxy would have been observed or not. However, it may well be true that the chances of detecting supernovae are somewhat higher for known supernovae, so the number of supernovae seen should be regarded as an upper limit.

© Copyright Astronomical Society of Australia 1997