Cepheid Epochs of Maximum and What They Reveal

Affiliation(s): VSS

Session details: Posters

Abstract

Most Cepheids are massive stars which evolve rather quickly compared to low-mass stars.  One way of studying this evolution is by tracking changes in the pulsation period as shown with epochs of maxima fitted to an O-C diagram.  Members of Variable Stars South and its predecessors have been active in this area. This poster shows the methods of doing that from the determination of mean light curves, the fitting of seasonal measures to these and the results.  Some interesting stars are examined in detail.

Biography

Stan’s astronomy began about 1960 and by 1965 he was observing variable stars visually. Attempts to monitor flare stars that way led to a project which saw a joint Auckland Observatory-University of Auckland project to build and use a photoelectric photometer. Commissioned in 1968, this was used until 1990 in a wide variety of projects, but mainly CVs and LPVs which are the stars he is most interested in. Until the mid 1980s they carried out the most effective photometry, to the faintest magnitudes, in New Zealand from the centre of NZ’s largest city!

Stan collaborated with Brian Marino and others in these projects, resulting in a good number of largely observational papers. Many highlights, but perhaps the best was the making of the first UBV measures of SN1987A and detemining from the colour changes on the second night that it was, indeed, a supernova.

A Chartered Accountant by profession, he is also a member of the Auckland Astronomical Society, Royal Astronomical Society, a fellow of the RASNZ and a member of Astronomical Photometry & Polarimetry, Binary & Multiple Star Systems, Pulsating Stars Commissions of the International Astronomical Union since 1970.  Stan is currently the Director of Variable Stars South. 

His observing these days is limited. Stan’s observatory is located at Waiharara (34.97S, 173.2E, 30M ASL) above the farm office.