20 July 2021 at 3:22 pm #584490
Good to see the data rolling in for this star. Many thanks to all observers. It’s been faint for a few days: I’ve have it at 16.6 yo 16.7 the last couple of nights.
Now the nights are getting a bit longer, some time-series photometry runs become possible.25 July 2021 at 5:28 pm #584508
Currently in outburst.28 July 2021 at 6:50 pm #584534Stewart John BeanParticipant
I am occasionally contributing to the present campaign on CG Dra with a V filter on iTEL 18 in Spain. Many of the results are being gathered using the CV method.
What systematic differences do we expect between the two?
Stewart28 July 2021 at 9:49 pm #584536
Looking at the light curve Stewart, there is not much difference. In any case, the objective of the project is to measure the time and duration of each outburst, rather than its precise mag. Thanks for your observation. If you are getting decent signal to noise ratio then stick with the V filter -after all, you are using a decent aperture scope. But no filter allows better SNR, so is often preferable with small telescopes.30 July 2021 at 1:18 am #584547Paul LeylandParticipant
Nights are moderately long (though dusty and/or smoky) in these parts.
The orbital period of 0.18864 days according to AAVSO appears well determined. What is the value of further lengthy observation runs? Is there a suggestion that the period may be changing or are we looking for flickering in the accretion disk?
I am prepared to spend some telescope time if it is worth my while but there other calls on it too.
(Added in edit: not that it makes any difference tonight. Complete cloud cover as of about 45 minutes ago.)30 July 2021 at 9:44 am #584548
Our earlier work suspectEd shallow eclipses. Can we confirm and does the depth vary with outburst status (outburst vs quiescence)?22 October 2021 at 4:05 pm #584826Stewart John BeanParticipant
Got a few images now from the AAVSOnet SRO telescope in the USA on CG Dra. It has been down for some time.
Hopefully more will follow.
Stewart10 May 2022 at 3:40 pm #610206
Had a run on CG Dra tonight.
Attachments:11 May 2022 at 1:34 am #610235
Thanks Max. There’s a lot of variation there. Not sure it’s regular though. Time will tell.
Keep up the good work!
Jeremy11 May 2022 at 12:18 pm #610236
Thanks, Jeremy! With tonight data..
Attachments:13 May 2022 at 1:56 pm #610309
More data on May 13th.
- This reply was modified 4 months, 2 weeks ago by Maxim Usatov.
Attachments:13 May 2022 at 5:32 pm #610313
Thanks Max. When I have a moment I’ll put it through Peranso to see if there are any signals.16 May 2022 at 12:47 pm #610330
Looks like it’s in outburst.
Attachments:16 May 2022 at 2:39 pm #610332
Yes, mag is certainly consistent with an outburst Max16 May 2022 at 6:11 pm #610333
Got some interesting result on the data collected. Although probably spurious, the period is really close to the 6h 22m +/- 26 m period for a matching K5 main sequence star mentioned in Bruch et al. (1997). I’ve never used FALC before, so not sure if this power is of any significance, likely not?
Attachments:17 May 2022 at 11:35 am #610337
Today CG Dra was at it’s brightest ever recorded during the past 2 years.
- This reply was modified 4 months, 1 week ago by Maxim Usatov.
Attachments:17 May 2022 at 12:25 pm #610344
Sorry for double posting, it looks like I only have limited time available to edit my previous post. The 6-h period disappeared with today’s data, so it was spurious and likely me not understanding how to use FALC. I now realize it requires manual manipulation with light curve segments to bring them down to the same magnitude level, so I dropped this idea. With today’s data, I have fitted a high-degree polynomial to “detrend” data assuming eclipses also occur in the outburst state, and many algorithms converge on a 4.52-h period appearing in the residuals. Although, still, more observations are obviously needed. I also wonder if I should search eclipses in the quiescent data only.
Attachments:18 May 2022 at 4:52 pm #610350
Worth looking for quiescence eclipses, Max. Accretion disc might be smaller then and thus more easily eclipsed22 May 2022 at 7:47 am #610436
30 s resolution, CV mode.
Attachments:23 May 2022 at 11:32 pm #610451
Another run with 30 s resolution. Refined ensemble selection and added visual ensemble/check star control – much better precision, albeit the seeing was pretty bad and clouds began to appear in the middle and near the end of the run. The routine handled the situations well. Hopefully fully prepared to try to catch those eclipses.
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