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.
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.
Project Leader: Stan Walker
The Mira stars are an interesting group of variable stars, well suited to visual observing. (And little observed in colours such as UBV) In most cases there is a quick rise to maximum brightness, followed by a slower decline to a rather faint level. The amplitudes are usually quite large, and the periods of 200-600 days make them easy to observe for the casual observer.
Amongst these stars there are a few unusual objects. These are Miras which, at times, show two distinct maxima minima. The most well-known of these stars in the 1960s were R Centauri and R Normae. Since then, two other southern objects have been observed – BH Crucis, discovered by Ron Welch in Auckland, and NSV 4721, now V415 Velorum, the existence of which was drawn to our attention by Peter Williams. The periods of these stars are all in excess of 400 days and usually 500 days. Colour photometry reveals another interesting feature, namely that the first maximum in R Centauri is bluer, hence hotter, than the second maximum, whereas the reverse is the case with BH Crucis.
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.
Principal Investigator: Augusto Damineli VSS Coordinator: Mark Blackford
Eta Carinae is now so bright that its 400-year long history of photometry risks being interrupted. Ironically, this could happen in a phase when we finally can see the central stars almost un-obscured. Very few CCD observers today are able to continue this historical monitoring since the star saturates with 1 sec exposure time even using small aperture telescopes.
Continued visual estimations are strongly encouraged to monitor long term trends; however, Augusto Damineli and other professional astronomers also require precision photometry data for their models.
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!
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.
Project Leader: Tom Richards
Rod Stubbings observed V745 Sco in outburst (mvis=9.0) on 2014 February 6.6 after observing it fainter than 13.0 24 hours prior. The nova has subsequently been confirmed by Paul Camilleri (CMQ) and Steve O’Connor (OCN), with more data coming in.
Jeno Sokoloski has requested as much photometry as possible and is also requesting spectroscopic follow-up from the community as well. Several professional researchers are already working on getting X-ray and radio data for this nova, and optical data from the AAVSO community will be very useful for comparison to other wavelengths.