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Eclipses No(s): 97
State: Rising
U/N/A-type eclipse.Attachments:
Eclipses No(s): 96
State: Quiescence
U/H?/PEHAttachments:
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
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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
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Eclipses No(s): 95
State: QuiescenceTypical U/N/A eclipse for this state.
Max
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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
Eclipses No(s): 94
State: QuiescenceThe 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
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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_periodMax
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It did went into bright outburst mode. I’ve been only able to collect 58 measurements this night due to clouds.
Max
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Thanks, Jeremy. Glad to be back.
Eclipses No(s): 93
State: Bright Outburst?It looks like CG Dra is rising into bright outburst mode – this is the brightest it’s been since the last bright outburst. A pattern could be emerging with the last outburst of the cycle being fainter than the previous one before bright outburst – but too early to tell.
Given that this should be an accretion disk (AD) dominated state where no bright spot should be promiment, a bright feature at phases 0.75-0.90, I think, can be interpreted as the re-emergence of the AD from the preceding fade that peaked at phase 0.75 – perhaps, due to the obscuration of a bright inner AD region by the stream overflow. The geometry should be compatible. Within this interpretation, this eclipse is V/L/S-type – V-shaped, no orbital hump, symmetric.
Max
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After a 2-week pause caused by a patch of bad weather, loss of power supply and Internet connectivity at the observatory – all at the same time…
Eclipses No(s): 92
State: Rising
Appears to be U/L/S eclipse, similar to the previous one (#91), just skewed due to rising magnitude. Old epoch is far off the minima, needs revisiting.Max
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In outburst, ~ 0.15 mag flickering.
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Unfortunately, the weather has been really horrible all these days… Managed to get a few data points here and there, but not enough to build a curve, so I haven’t been posting. Tonight the clouds have interrupted the session only early in the morning – so good data.
Eclipses No(s): 91
State: Rising
Typical accretion disk-dominated U/L/S eclipse. We need a new period/epoch analysis, as the old one appears to be inaccurate.Max
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Robin,
Incredible result! I wish there would be a workshop or something showing how this was done – from observation to processing.
Max
Eclipses No(s): 90
State: Fading
U/L/S eclipse, PEH has disappeared.Attachments:
Gianni, I am afraid I will be unable to understand Italian – but looking forward to an article in English. 🙂
Eclipses No(s): 88, 89
State: FadingTwo U/L/PEH + U/L/PEH eclipses. Accretion disk fading in brightness. There are two short post-egress brightenings of the same profile on both eclipses, peaking at exactly phase 1.14, so this is likely a PEH feature and not a flickering artifact. This is easily seen on the phase plot as post-egress magnitudes are a little different and one PEH appears to be on the top of another one. The bright spot appears to be compact or partially obscured by something, as it is not a smooth hump.
Max
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Eclipses No(s): 87
State: FadingSurprising curve today on the way down – broad U-shaped profile, highly asymmetric, no orbital hump. Very extended post-egress brightening all the way from phase ~ 1.15 to 1.50 – almost as if the bright spot is on the wrong side of the eclipse. Assuming this can be called a post-egress hump, except that it is a very broad one, this curve can probably be classified as U/L/PEH. We have seen this profile during the fade on June 30th except that back then the PEH was much narrower.
What causes such variation of minima shapes – this “U” is extremely broad – bright and very extended accretion disk?
Wild speculation, again, on the magnetic theme. Can CG Dra’s WD magnetic field switch on and off, sometimes turning the system to something resembling a polar? The patchy stream of material can block the bright spot at phase ~ 0.8, resulting in lower ingress flux, compared to egress. This U/L/PEH curve is somewhat similar to HU Aqr and SDSS J093537.46+161950.8 which Hardy et al. (2017) describe as a “typical polar.”
Seeing overall was very good tonight – there are interesting flickering oscillations towards the end of the curve. Note some fast flickering episodes reach close to 0.2 mag in amplitude.
Max
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Gianni, it would be interesting to read more about your atmosphere project. If sky pollution is an issue then a lot of projects are to be done in the solar system, including automating observations of the solar photosphere and chromosphere, nightly monitoring of the planets and the Moon, and so on. Lots of inspiration in the BAA Journal.
Eclipses No(s): 86
State: OutburstV/L/S-type eclipse (V-shaped, low or none orbital hump, symmetric), expected for the outburst. I find this state to be the most interesting, as almost every light curve is unique. Very good data quality with check star sigma ~ 0.016 mag, revealing the flickering dynamics. Interesting “fading” wave after the egress.
Max
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