In the last week I have added another item on the BAA Forum about this star under the heading "What's happening to Z Ursae Majoris?". This is what I said:-
"You might have noticed that Z UMa has just recently reached a peak in its brightness and this peak was brighter than previous peaks for the last four years (see the attached screen shot from the BAAVSS database). I am going to stick my neck out here and make a bit of a prediction! I think we will see more of this in the next four years with more sharply defined peaks and troughs and a wider range in magnitudes. My reasoning is the interplay between the two periods of pulsation that this star shows. If you look back to 2016-2017 there was a period then when the amplitude of variation died away somewhat and there was evidence for double peaks in the pulsation prior to this. Then the variation recovered and there were more sharply defined peaks and troughs. I think we are now seeing a repeat of this behaviour.
Why do I think this? Well, I am not sure I believe that the second, less prominent, pulsation period in this star is dying away. I think that this modulation of the amplitude and the double peaks (see above) is evidence that the two pulsation periods in this star are still operating together and causing the modulations to the primary pulsation period that we see. Over the next four years we will probably see these sharply defined peaks because the two periods are acting in concert and then after this they will go out of phase and we will see the return of the double peaks and the lower amplitude range. We shall see! For more on this read my previous posts on this subject."
Well, interestingly my post elicited no response from other members at the BAA at all and sometimes I think I am just talking to myself. It is difficult to know whether they find what I am saying is interesting or whether they just think it is boring, or perhaps worse still, they think I am wrong but they are too polite to say! I will be interested to see if my prediction turns out to be true. If it is I think that John Greaves may be wrong in suggesting that the two periods of pulsation in this star are unifying to one and that it may be premature to say that this star is becoming more Mira like.
One of the projects I am thinking about starting is to see if I can process this data for myself. It will involve me trying to learn a new computer language like Python but I may try and see if I can use AI to construct it to save some time. The first job would be to bin up this data and see how well defined it is. For example, it may be easier to see how frequently the double peaks occur as I reckon these are indicative of dual periods in the pulsation. Watch this space!
All text and images © Duncan Hale-Sutton 2025 (except the images kindly provided by the BAA).
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