CG Dra: a VSS campaign

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  • #584490
    Jeremy Shears
    Participant

    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.

    #584508
    Jeremy Shears
    Participant

    Currently in outburst.

    #584534
    Stewart John Bean
    Participant

    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?

    Stewart

    #584536
    Jeremy Shears
    Participant

    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.

    #584547
    Paul Leyland
    Participant

    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.)

    #584548
    Jeremy Shears
    Participant

    Our earlier work suspectEd shallow eclipses. Can we confirm and does the depth vary with outburst status (outburst vs quiescence)?

    #584826
    Stewart John Bean
    Participant

    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.

    Stewart

    #610206
    Maxim Usatov
    Participant

    Had a run on CG Dra tonight.

    Attachments:
    #610235
    Jeremy Shears
    Participant

    Thanks Max. There’s a lot of variation there. Not sure it’s regular though. Time will tell.
    Keep up the good work!

    Go well!
    Jeremy

    #610236
    Maxim Usatov
    Participant

    Thanks, Jeremy! With tonight data..

    Attachments:
    #610309
    Maxim Usatov
    Participant

    More data on May 13th.

    #610313
    Jeremy Shears
    Participant

    Thanks Max. When I have a moment I’ll put it through Peranso to see if there are any signals.

    #610330
    Maxim Usatov
    Participant

    Looks like it’s in outburst.

    Attachments:
    #610332
    Jeremy Shears
    Participant

    Yes, mag is certainly consistent with an outburst Max

    #610333
    Maxim Usatov
    Participant

    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?

    Max

    Attachments:
    #610337
    Maxim Usatov
    Participant

    Today CG Dra was at it’s brightest ever recorded during the past 2 years.

    Attachments:
    #610344
    Maxim Usatov
    Participant

    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.

    Max

    Attachments:
    #610350
    Jeremy Shears
    Participant

    Worth looking for quiescence eclipses, Max. Accretion disc might be smaller then and thus more easily eclipsed

    #610436
    Maxim Usatov
    Participant

    30 s resolution, CV mode.

    Attachments:
    #610451
    Maxim Usatov
    Participant

    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.

    Attachments:
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