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Category: VSS Symposium 4
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VSS Symposium 4 Files: 9
On 25th March 2016, VSS held our 4th Symposium at NACAA 2016 in Sydney. Slides (where publication was allowed) can be accessed here.
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Past, present and future for the EA binaries project Size Filesize 194.89 KB
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Margaret will present a summary of the work achieved and published to date. This includes two papers published by the JAAVSO, with a third paper in preparation. Few new data sets on any targets are now being received. However, both David Moriarty and Margaret Streamer are collecting data in several band passes over the full orbital cycle for specific targets. These data will lead to preliminary astrophysical modelling of the systems. However, for precise mass determination, orbital radial velocity measurements are needed. These can be determined from spectroscopy and given the magnitude range of project targets, telescopes larger than a typical amateur telescope are required. To this end, I have collaborated with two professional astronomers (at the Australian National University and University of Sydney) to obtain spectral data for TT Horologii, a binary with a delta Scuti component, using the ANU 2.3m telescope at Siding Springs. The future for the EA binaries project is very sound. 1) There remains plenty of opportunity for beginners to be involved with the many targets for which we still have very little data. 2) For the more adventurous, there are plenty of targets waiting to have preliminary models determined. 3) Hopefully, I shall continue my partnership with the professional astronomers to enable future access to the big telescopes so that the precise astrophysical properties of the systems can be determined.

Light Element Determinations - Lessons Learned from "Revised Light Elements of 78 Southern Eclipsing Binary Systems" Paper Size Filesize 2.92 MB
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During preparation of the "Revised Light Elements of 78 Southern Eclipsing Binary Systems" paper, numerous pitfalls for Analysts were discovered. This paper is a combination of lessons learned from that and a description of new techniques developed then and later.

The Visual Observation of some interesting Long Period Variable Stars Size Filesize 5.95 MB
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The presentation describes the author's long term visual monitoring program of a large number of long period variables between declination 10S and 60S. It discusses the aims of the program, the simple telescopic equipment being used and some initial results and insights. It hopes to dispel the myth that long period variable stars are predictable and mundane with some examples of stars which show humps on the ascending portions of their light curves, standstills as well as the useful activity of establishing periods and amplitudes for some lesser known southern NSV stars.

Long-term oscillations in the orbital period of RR Cen: third body or Applegate effect? Size Filesize 774.36 KB
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RR Cen is an EW-type contact binary that has been continuously observed since 1894. The first calculation of orbital elements and basic modelling were performed by South-African-based Scottish astronomer Alexander Roberts in 1903, and subsequent models had been computed by Knipe (1965), Bookmeyer (1968), King and Hilditch (1984) and Yang, Quian, Zhu et al. (2005) (YQZ). The density of this coverage has provided a good data set for observing changes to the orbital period, and YQZ computed a linear increase in orbital period, which they attributed to mass transfer, coupled with a small 60-year sinusoidal variation in orbital period, which they attributed to a third body in the system. Subsequent observations, including those by VSS members Mark Blackford and Jonathan Powles in 2014-2015, reveal the orbital period increase to itself be part of a sinusoidal oscillation with a longer, 90-year period and much larger amplitude. This paper suggests that a better explanation for such periodic variations would be the Applegate effect - regular oscillations caused by the consequences of the magnetic field cycle of one of the stars - however this theory too has problems in its applicability to a star of such early classification (F0). 

Plumbing the Depths - The problems of measuring eclipse minima Size Filesize 403.5 KB
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Measuring the minimum of an eclipse light curve has practical and theoretical difficulties. The two common methods - Kwee & van Woerden and polynomial fitting, often disagree significantly. This talk will discuss various methods, their good and weak points, and when and how best used.

Video Method for Observing Eclipsing Binaries Size Filesize 1.56 MB
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In this talk I will present the video method for observing of eclipsing variable stars which we used in 2015 to obtain more than 70 times of minima.

An improved method for correcting atmospheric extinction Size Filesize 1.87 MB
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The standard method for measuring and correcting for extinction by the Earth's atmosphere is well known. However it requires 'photometric' conditions, i.e. the extinction must be constant across the entire sky and for the whole night. Due to our maritime climate, these conditions are very rare in New Zealand (and I expect it is similar in Australia but the audience is sure to tell me if I'm wrong). Approximately 30 years ago, the Vilnius Observatory developed another, little known, method for measuring and correcting extinction that can cope better with less that photometric conditions. This presentation will describe this method, which I hope will allow us to reduce the systematic error in our results that comes from applying incorrect extinction coefficients.

Deciphering the Enigma of QZ Car Size Filesize 6.7 MB
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The four main components of QZ Car form a pair of close binaries that share a wide orbit with a period of about 50 years. Observing this system is not really as simple as 'two binaries for the price of one', however, as these massive young stars are involved in complex processes of interaction. The present authors have been trying to piece together a comprehensive picture of the system for some time. A review of the various aspects of this effort brings out, in the one target, many of the more general issues in close binary research.

Some Stars Do & Some Stars Don’t – Reflections on 45 Years of Variable Star Observing Size Filesize 9.35 MB
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The author reflects on his long term involvement in amateur astronomy and many years of visual observation of variable stars. There are some memorable events during this time, some personal achievements and some results of research on specific stars.


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