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International Year of Astronomy | American Association of Variable Star Observers (AAVSO)
Privacy Policy | Contact Us | Affiliates | About Us | Participant Sites
International Year of Astronomy | American Association of Variable Star Observers (AAVSO)
I just submitted my first observation of Zeta Phoenicis via the AAVSO'sWebObspage. I used "Southern Gems" as the Chart ID. We will have to use that submission method until the Citizen Sky submission page lists the Southern Gems stars. The chart and comparison stars (I used 39 & 42 on this occasion with an estimate of mag 4.0) were clear and easy to use. Thanks Sebastian. I used unaided and binocular views, but found the latter to be easier from my at-times light-polluted suburban location. My binoculars fogged up just when I was about to attempt a Kappa Pavonis estimate, so I called it a night. Regards, David
Hi,David, there is a long history of observations and papers for these stars and they are both very interesting. Zeta Phe is an eccentric system that shows apsidal motion caused by a third star orbiting the eclipsing pair. This causes min II to change in orbital phase with time if we use a fixed period for the primary eclipse (of course it's the orbital plane that changes its inclination with respect to our line of sight). So if we observe long enough we will see that effect taking place. The period of the third body is 221 years according to http://arxiv.org/abs/0711.3980
The current periods are determined with years and years of photometric data, althoguh that doesn't strictly mean that the catalogues are listing the most up to date values. We have alrady discussed that lCar and kap Pav undergo period changes and the current values are different from the catalogued ones!
Kappa Pav may change its period again any time soon. It has changed by as much as 40 min. in the past (extreme values) which is a lot for a cepheid variable. Continuous monitoring reveals that as phase shifts in the light curve when we use a fixed period to plot the observations.
So these two stars have something in common: if we use a fixed period for them we'll see that the light curve will show wandering datapoints if we wait enough years to see it. Yes, you can use those charts, the comparison stars will be basically the same but with the AAVSO format.
The charts are ready we are only waiting to finish the tutorial to make the final pdf. But it's better that we all use the same charts so I am attaching them here. Cheers,
Sebastian.
Hi Sebastian Thanks for attaching the charts for the two stars. They are very clear! Thanks also for the paper reference and providing details of interesting aspects of zet Phe and kap Pav. Getting back on my hobby horse of "where's the data dude?", I wonder just how often data is obtained for particular studies but not contributed to the AAVSO International Database (AID)? Reading the zet Phe section in the paper you cited, we see:
"The unfiltered light curve was observed in 1950’s by Hogg (1951), after then by Dachs (1971) in UBV filters, and the best one by Clausen et al. (1976) in ubvy filters."
"Our new photoelectric U BV observations were secured with the modular photometer utilizing Hamamatsu EA1516 photomultiplier on the 0.5-m telescope at the Sutherland site of the South African Astronomical Observatory (SAAO) during two weeks in September 2005."
These comments point to (at least) 4 photometric data collection efforts. But where is the data for these? Sitting on individual researcher or research institution's hard drives (or tapes/cards for the older data)? Do you think this happens often, rather than such data being submitted to AID? This has two obvious negative consequences: 1. How can the results of such papers be checked (i.e. how can the "experiments" be repeated)? I'm sure the authors would share their data if requested though. 2. The data is not available for posterity, analysis of change over time etc. I realise this is outside of the scope of Southern Gems, but it seems like an interesting question to me. It's cloudy at the moment, so no estimates tonight... Regards, David