CG Dra: a VSS campaign

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  • #612800
    Maxim Usatov
    Participant

    It did went into bright outburst mode. I’ve been only able to collect 58 measurements this night due to clouds.

    Max

    #612950
    Maxim Usatov
    Participant

    Hi All,

    Strange things going on… The timing of minima keeps sliding. I’ve plotted the minimum a few days ago and it was right on the observed minimum. Tonight it is about 0.2 phase off. There is very little data, as it was shot through the hole in the clouds, but the eclipse was captured. Either this is a bug in my code or the period keeps changing. But the code here is rather straightforward – I get the epoch time and simply add periods to it to plot lines. How can a period drift by 0.2 phase in such a short period of time?

    Code:
    if self.plot_epoch > 0 and self.plot_period > 0:
    extrema = []
    current_extrema = self.plot_epoch
    light_curve_start = light_curve[“DATE”].min()
    light_curve_end = light_curve[“DATE”].max()
    while current_extrema < light_curve_end:
    if light_curve_end > current_extrema > light_curve_start:
    extrema.append(current_extrema)
    print(“Ephemeris extrema:”, current_extrema)
    ax0.axvline(current_extrema – 2400000.50, color=”green”, linestyle=’–‘)
    current_extrema = current_extrema + self.plot_period

    Max

    • This reply was modified 1 month, 3 weeks ago by Maxim Usatov.
    Attachments:
    #612953
    Jeremy Shears
    Participant

    Hmmm…that is very odd Max. Could it be the recent dip is a random fluctuation rather than an eclipse?

    #612954
    Maxim Usatov
    Participant

    I don’t think so. Hopefully more data will follow.
    Max

    #613045
    Maxim Usatov
    Participant

    Eclipses No(s): 94
    State: Quiescence

    The eclipse minima definitely has shifted or there is an error in how I am calculating minima. I am puzzled. Can O-C analysis be done in Peranso or some other software?

    Max

    Attachments:
    #613050
    Jeremy Shears
    Participant

    Period analysis can be performed using one of Peranso spectrum analysis tools. But these analyse the data globally, resulting in significant periods being identified, rather than calculating the ToMin that would be required for O-C analysis.

    #613054
    Maxim Usatov
    Participant

    Just double-checked my minima calculation: MetroPSF provides the same ephemeris as Peranso, so looks like there is something going on with periods here. I just wonder if there’s an automated way to identify observed minima of all ~ 90 eclipses we have, or is manual the only way? Anyone brave enough to do O-C analysis? 🙂

    Max

    #613057
    Maxim Usatov
    Participant

    Eclipses No(s): 95
    State: Quiescence

    Typical U/N/A eclipse for this state.

    Max

    Attachments:
    #613059
    Maxim Usatov
    Participant

    Thinking how to automate ToM detection for the data collected so far, I have tried fitting a Gaussian function and finding its minimum – see screenshots attached for the last eclipse recorded. Unfortunately, this method is very sensitive to the data boundaries if the data is noisy. If I include more points to the left or right, I get a different curve fit. Even the Kwee-van Woerden method displays the same sensitivity in Peranso. Attached are a few examples. I was thinking to try to find ToM automatically using some predefined phase shift, say, delta phi = 0.2, from calculated minima to set search boundaries, but the choice of delta phi produces different ToM results with both Gaussian fits and the KvW.

    Max

    #613064
    Maxim Usatov
    Participant

    OK, I have managed to do Gaussian fits. First, I define a delta phi search region, then identify the faintest magnitude within the search region, smooth out the noise, determine eclipse well and then fit a Gaussian curve to the well. Presenting the first O-C table. Looks like it’s linear. ANOVA period determined incorrectly?

    Max

    Attachments:
    #613067
    Maxim Usatov
    Participant

    Eclipses No(s): 96
    State: Quiescence
    U/H?/PEH

    Attachments:
    #613200
    Maxim Usatov
    Participant

    Eclipses No(s): 97
    State: Rising
    U/N/A-type eclipse.

    Attachments:
    #613249
    Maxim Usatov
    Participant

    Flat O-C (ignore a few outliers) with P=0.188644 d.

    #613270
    Maxim Usatov
    Participant

    Eclipses No(s): 98
    State: Quiescent.
    U/N/A-type eclipse.

    Attachments:
    #613273
    Jeremy Shears
    Participant

    Looking good Max. Any ideas about outliers? I’ve sometimes struggled to assign proper ToMs in specific eclipses, especially small ones, when the underlying light curve has been busy with bumps and humps.

    #613279
    Maxim Usatov
    Participant

    These are exactly the cases where the algorithm has failed to fit a Gaussian due to noise or partial data. I also need to resample the data to a finer grid, as described by KvW, to refine the result.

    #613284
    Jeremy Shears
    Participant

    Thanks Max. I suspected this was the case. But ignoring these, the O-C is looking good 👍🏻

    #613323
    Maxim Usatov
    Participant

    Eclipses No(s): 100 (didn’t show a pic for 99th, partial data)
    State: Outburst
    U/L/S-type eclipse.

    Attachments:
    #613325
    Jeremy Shears
    Participant

    Congratulations on the century, Max! Very nice work, indeed.

    #613326
    Maxim Usatov
    Participant

    Thank you very much for organizing this, Jeremy!

Viewing 20 posts - 161 through 180 (of 191 total)
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