27th Feb - A Productive Evening

[coatesg]

Quite a productive evening before the cloud thickened (before the deluge today...). 

Two HADS light curves:

These both contribute to the ongoing HADS study @Dave Smith and I (and others!) submit data for.

FS CMi: period of 1.14hrs so quite quick this one.

V447 UMa - another one varying by 0.5 mag over the space of 1.7hrs. I do wonder if this is multiperiodic given the smaller magnitude (brighter) in the second maximum compared to the first?

 

Eclipsing Binary LM Boo (EW type) : 

AAVSO has period as 7.8702hrs. I used the "minima" software to analyse the curve and pinned the minimum down to HJD 2458907.5255 +/-0.0001. Have submitted this to hopefully be published in the JAAVSO in their eclipsing binary minima roundup. The minimum is quite a way off the ephemeris on the AAVSO VSX record - the last observation in the Lichtenknecker Eclipsing binary database is from 2016 and is similar in O-C.

Data went a bit haywire at the end due to cloud. 

To check the calculated minimum plot the curve forwards and backwards around the ToM - should be pretty much coincident either side:

 

Edited February 28, 2020 by coatesg

[Dave Smith]

Wow you have been busy! That Minima software looks interesting, I must give it a try.

Dave

[coatesg]

Taking advantage of a clear evening! It's absolutely wazzing down tonight like it seemingly has been since Oct...

It's the first time I've used Minima - it's fairly easy to use from first looks (though how much to rely on the error calcs, I'm not sure!).

I had tried Peranso (which has much more functionality) before on a trial install, but I do relatively little EB work and so the $49 cost seemed a bit excessive... 

Edited February 28, 2020 by coatesg

[Dave Smith]

Thanks Graeme. I do have Peranso and have found it useful for combining results from different occasions to get a phase diagram and hence an accurate time period. However I haven't tackled an eclipsing binary for some time now. HADS stars are so convenient in that you can start at any time.

Dave 

[coatesg]

Absolutely! It took a fair bit of browsing around ephemerides to find an EB with a predicted eclipse at the right time (why are they always at the wrong time?! 🤷‍♂️).

Luck has it that the last observation in AAVSO for this star was about 2 yrs ago as well, 4 yrs in Lichtenecker.