Photoelectric Photometry Newsletter

Message from the Editor

A few weeks ago, I had the pleasure of attending a symposium at Yale University, in honour of the 90th birthday of Dorrit Hoffleit. Dorrit has made many and diverse contributions to astronomy. She was the second recipient (after Carl Sagan) of the American Astronomical Society's Annenberg Award, for outstanding contributions to astronomy education. Her research has spanned many fields, including variable stars. She has authored many interesting papers on the history of astronomy. She has served the AAVSO in many ways, being President in 1961 and 1962. To AAVSO photometrists, however, she may be best known as the editor of the Yale Catalogue of Bright Stars, which contains a gold mine of authoritative information about most of the stars in our program. Compiling catalogues is not a glamourous activity, but it is absolutely essential. The Yale Catalogue of Bright Stars is the most used and appreciated item on my bookshelf. I thank Dorrit for that and, on behalf of the AAVSO Photoelectric Photometry program, I wish her many more years of good health and happiness.

The AAVSO Eclipsing Binary program and committee has recently compiled the fruits of many years' labours, in the form of times of minima, and (0-C) diagrams of about 100 EB's on their program. The co-authors are Marvin Baldwin and Gerard Samolyk. For a photometrist, it is interesting to look through these compilations, and be reminded that there are many EB's which are bright enough for photoelectric photometry with small telescopes. Beta Lyrae and Beta Persei are obvious examples, but there are also stars like R CMa and Delta Lib which are 5th magnitude or brighter. If you would like more information on the AAVSO Eclipsing Binary program, contact the chairman of the EB committee: Marv Baldwin, 8655 N. Co. Rd. 775E, Butlerville IN 47223.

In a recent paper "Hotspots on Late-Type Supergiants" (Monthly Notices of the Royal Astronomical Society, 285, 529-539 (1997)), P.G. Tuthill, C.A. Haniff, and i.E. Baldwin report on interferometric imaging of Alpha Ori, Alpha Sco, and Alpha Her. They conclude that, in each of these stars, there are one to three unresolved features or "hotspots" which contribute between 5 and 20 per cent of the light. These seem to vary on time scales of 3 to 9 months, and are "thus consistent with a convective origin". These hotspots may be responsible for some of the light variations in these stars - two of which (Alpha Ori and Alpha Sco) are on the AAVSO photoelectric program.

Recent correspondence reminds me to remind you: your transformation coefficients should be determined at least once a season, and any time you make a significant change in your instrumentation. If you use red-blue star pairs to determine your transformation coefficient, you should use at least two, and preferably three pairs.