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Another good night. Outburst appears to be leveling off at a fainter magnitude. Ingress hump not as pronounced.
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Today’s data. CG Dra on the rise. The gap in data during the eclipse coincides with the GEM meridian flip. Eclipse also partially visible at the beginning of the session. Pretty stable atmosphere tonight with 0.025 sigma on the check star despite all the heat – could barely cool the sensor down to -20C at midnight. Hot spot (?) hump visible prior the eclipse, along with the gentle egress.
It is interesting also to observe how nights are different “photometrically” as the processing pipeline is fixed. I think this is the most tight data of all so far.
Max
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Thanks, Jeremy!
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Back to monitoring. Severe turbulence at the beginning of the session as the telescope was still cooling down, but I thought I’d remain this in the dataset as it appears to capture the ingress hump (hot spot?) I think that it’s another eclipse near the end of the session in the morning when SNR began to decrease. Period precision keeps improving.
Max
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Squeezed one more run before the break.
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AoV fitting.
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Data from today, at quiescence. High-quality measurement, also asymmetric profile with gentler egress. Looks like a hot spot. Later into the night a single 0.2 mag brightening point – is this something like a flare? I am going to take a break until June 4th, hopefully to continue monitoring CG Dra on return.
Max
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Data from today, at quiescence. Noisy data, as we approach 17th mag, and the seeing wasn’t perfect. Looks like we see another pair of eclipses with an asymmetric profile. Looking at various literature breaking down DN light curves, I think this curve can be explained with a low-inclination grazing eclipse and a hot spot responsible for the ingress hump. Things going through my head:
1) If CG Dra has developed a hot spot and switched to asymmetric profile, how typical this state switching is for dwarf novae?
2) Is there any user-friendly light curve modeling software so we could try to build a model of the system to fit this data?Max
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Yes, all three coincide except that the minima of the first one visually appears to have occurred earlier than calculated:
5/23/2022 22:45:13 2459723.44807 59722.9480699999 OBSERVED (EARLY)
5/24/2022 03:16:52 2459723.63671 59723.1367100002 OBSERVED
5/26/2022 00:33:17 2459725.52311 59725.02311 OBSERVEDI have estimated ToM using Peranso and numbers from Shears et al. (2008).
Max
Today’s data. If this is an eclipse, what would explain that it didn’t fully recover until about 3.6 hours later?
Max
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Thanks, Jeremy!
Today’s data – really interesting. Note the eclipse profile is asymmetric with what appears to be a gentler egress on the first event. The second dip is ~ 0.1898 d from the first one, so looks like I was lucky and that is the second eclipse this night, also with a gentle egress. Could be something going on with the accretion disk?
Seeing conditions improved later into the night, with better precision on the second eclipse. Periodic interruptions in the light curve are refocusing events at 30-minute intervals. The telescope decided it wants to autofocus near both minima. I’ll increase the period to 60 minutes to minimize this effect.
If I combine this data with the previous night’s run (with polynomial fit to remove the trend) I get 0.189617 +/- 0.07808 d period reported using the ANOVA algorithm, which appears to be in good agreement with the 0.1893 +/- 0.0006 d period used by Bruch et al. (1997).
All the data is in AAVSO and BAAVSS databases.
Max
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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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30 s resolution, CV mode.
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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
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Today CG Dra was at it’s brightest ever recorded during the past 2 years.
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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
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Looks like it’s in outburst.
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More data on May 13th.
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Thanks, Jeremy! With tonight data..
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Had a run on CG Dra tonight.
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