William Henry Wehlau (1926–1995)

In late February 1995 William Wehlau suffered a fatal stroke while in Cape Town attending the Colloquium on Astronomical Applications of Stellar Pulsations. Born on 7 April 1926, he completed his early education in San Francisco before being drafted into the US. infantry in which he served in combat from 1944 to 1946 in the Philippines and later was part of the Army of Occupation in Japan Returning to California he resumed his education, receiving his Bachelor of Arts in 1949 and his Ph.D. in 1953, both from the University of California, Berkeley. After two years as an instructor at the Warner and Swasey Observatory, he took up a Postdoctoral Fellowship at the University of Western Ontario in 1955, where he joined the faculty in 1957, and was promoted to Professor in 1961. For the next thirty-five years he had an important influence on the direction of Canadian optical astronomy both by promoting international collaboration and by developing the Department of Astronomy at the University of Western Ontario.

With the active development of 4-meter class telescopes by the Europeans, US.A., U.K. and Australia in the early 1960s it was clear to some that to remain competitive, Canadian astronomers would have to either collaborate in the construction of a similar sized telescope or even build one of their own. After a failed initial proposal to collaborate in a British Commonwealth telescope in Australia, Bill fired one of the first shots in a revived campaign in May 1964 in a talk at the annual meeting of the Royal Astronomical Society of Canada held in Ottawa. He urged the construction of a telescope of at least 150 inches diameter "To maintain and enhance the reputation of Canadian astronomy." His plea was reported in a number of Canadian newspapers and received favorable editorial comment.

Later that same year we learned that a 4-meter optical telescope, the Queen Elizabeth II Telescope, would be erected on Mount Kobau in southern British Columbia. After some two years, as a mirror blank was cast and a road built up Mount Kobau, a strong division of opinion developed because the quality of the site seemed inferior to those of other large telescopes and there were attractive offers for Canada to collaborate in other large telescope projects, particularly in the southern hemisphere. This division led to a Working Group set up under D. C. Rose of Carleton University to review the whole Canadian large telescope situation. Bill was the only active astronomer among the four Working Group members. He was an excellent choice because of the sensitive situation. The Working Group held town-hall meetings with astronomers across Canada and produced an excellent carefully worded report in the summer of 1968 which bore the stamp of Bill's quiet erudition. Funding for the Queen Elizabeth Telescope was canceled in 1968.

Ultimately, this report led to a highly successful collaboration between Canada and France in the 3.6-meter Canada-France-Hawaii Telescope for which an agreement was signed in 1974. Bill played a major part in the negotiations, which began in 1972, and he served first on the Scientific Advisory Committee and later on the Board both as member and chairman between 1974 and 1985. In 1991 Bill was again asked to chair a committee to review Canada's bid to join the Gemini twin 8-meter telescope project. Canada officially took a 15% share in this exciting venture in 1993.

In the early '60s the principal centers of astronomical activity in Canada were the Dominion Observatory and the Dominion Astrophysical Observatory, both supported by the Canadian Government, and the University of Toronto Astronomy Department. But in 1966, Bill's determined efforts led to the formation of the Department of Astronomy at UWO. He became the first Head (which he remained until retirement in 1991) and, in 1968, the University's 1.2-meter telescope at Elginfield saw first light largely as a result of his efforts. The Department and the Observatory have provided training for several generations of graduate students and are recognized for their world-class studies in stellar astrophysics: from cool atmospheres to hot winds, surface magnetism to interior structure and stellar variability at many timescales. The UWO Observatory also developed a strong reputation for high-quality Coudé and Cassegrain spectroscopy, polarimetry, and globular cluster photometry. Some of the first stellar infrared spectra in Canada were obtained there with a Fourier Transform spectrometer developed by Bill in collaboration with Moorhead of the Astronomy Department and Lowe of the Physics Department.

At a time when such interactions were hindered by bureaucracy and poor communications, Bill encouraged fruitful scientific collaborations between astronomers in the former Soviet Union and Canada, through formal exchanges between UWO and the Astronomical Council in Moscow. He was one of the few western astronomers to observe with the 6-meter telescope of the Special Astrophysical Observatory.

Bill maintained an active research career even after retirement and much of his work was truly pioneering. His eady studies on least-squares analysis of pulsating star light curves laid the foundation for the period searching techniques commonly used today. In the 1950s he obtained high-dispersion spectra of chemically peculiar stars and searched for rotational variability. With Moorhead and Lowe he observed abundances in the Orion Nebula using the 1.2-meter telescope. Using the Michelson dynamic interferometer on the CFHT in 1986 he set important limits to the abundance of HeH⁺ in the planetary nebula NGC 7027.

In the 1980s, Bill's interest and experience in stellar pulsation and chemical peculiarity finally converged in the study of the rapidly oscillating Ap stars. He was one of the first to recognize the potential diagnostic power of this new class of rapid variables, while many astronomers remained skeptical about their reality. Bill's efforts to map the surface abundances of Ap (CP2) stars were pioneering. He had always shown great respect and admiration for the work of Armin Deutsch and his attempts to develop a technique for surface mapping of Ap stars. As he had for roAp stars later in his career, Bill had the knack to recognize a potential astrophysical goldmine, taking a very early interest in looking for the line profile variations that should be visible because of the non-homogeneous distribution of abundances on the surfaces of Ap stars. At a meeting on Ap stars held in Baltimore in 1967, he delivered a paper on Chi Serpentis where he mentioned looking for the expected line profile effects in his photographic spectra. Subsequently he was involved in one of the two major efforts to apply Deutsch's method to other Ap stars.

In 1974, Bill and Alfred Falk published a paper applying the Deutsch technique to line profile variations, with the hope of recovering information about a star's surface. The poor quality of the photographic spectra prevented the idea from being properly tested. In 1979 Russian astronomers who were developing digital computer techniques to invert the information in stellar line profiles to obtain surface structure asked Bill and his former graduate student, John Rice of Brandon University, to obtain high signal to noise spectra of Ap stars with electronic detectors at high resolution to test their program. Thus began a very productive international collaboration which eventually expanded beyond Canada and Russia to include Austria, Finland and the U. S., and produced a series of papers with maps of surface abundance and temperature for both hot and cool stars. Bill was an active member of two IAU Commissions and at the time of his death was President of the Working Group on Ap and Related Stars.

In addition to his life in science Bill enjoyed a very close family life. He is survived by his wife Amelia, also an astronomer, his four children, Ruth, Jeanne, David and Alice, and two grandchildren. We have lost a great friend. Not only was Bill a pioneer in science but he quietly helped Canadian astronomy maintain its place on the international stage.