CCD photometry
CCD cameras have long been used in the production of “pretty pictures” – the wonderful astrophotographs that we see in magazines, books and websites. However, CCD cameras also have a long history of scientific study, and with the plethora of commercial and free photometry software, they have become the mainstay of amateur research activities.
Projects for CCD photometry
Note that like Visual Observing, this area of research within VSS is based around the technique of observing, rather than purely the nature of the objects being studied. Some of the projects below therefore overlap with the research areas that focus purely on specific types of variable stars.
Eclipsing Binaries – Insight into Stellar Evolution
Coordinator: Tom Richards
“Everybody knows” that wide, visually separated binaries provide an indispensable first step to astrophysics as well as the distance scale ladder. All we need to know is their distance by parallax methods, their orbital period P, and the apparent size of the orbit. True orbit follows, then their masses. Magnitudes at that distance give true luminosities which with their colour gives temperatures, thence their size. There’s no other way of making this first interstellar step.
QZ Carinae
Project Leader: Stan Walker
One of the most difficult observing targets in our galaxy is QZ Carinae, a massive EB system. It comprises four stars arranged in two pairs: an eclipsing secondary pair with a period of 5.99875 days and a non-eclipsing primary pair with a period of 20.74 days. Masses are 16.7 and 28.0, and ~40.0 and ~9.0 respectively. Separation of the two pairs is about 50 AU and the absolute luminosity about –7.5. It’s almost naked eye at 2500 parsecs!
V0454 Carinae spectroscopic and photometric campaign
Campaign Coordinator: Mark Blackford Professional Advisor: Ed Budding
Ed Budding and Roger Butland are currently investigating this relatively bright but neglected eclipsing binary (range 6.96 to 7.16 V Mag, period 0.980417d). They’ve measured radial velocities from high resolution spectra recorded with the HERCULES spectrometer on the 1m McLellan telescope on Mt John and proposed that V0454 Car is probably another quaternary system – not unlike QZ Car, but a bit less massive.
The RV curve of the close binary system (eclipsing pair) is well covered, and they can get a reasonably good picture of it from both its set of spectral lines. However, the third component shows unexpected short-term variations superposed on a much longer-term trend. They think that it is in a binary arrangement with a lower mass companion having a period of order a week or two. However, they don’t have enough information to form a very clear picture at the moment.