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CG Dra in quiescence. Looks like a U/N/A type eclipse of accretion disk and a bright spot.
Max
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CG Dra fading, pair of eclipses visible, medium quality data. The latter appears to be of U/N/A type – U-shaped, normal orbital hump height, asymmetric. The former eclipse was interrupted by clouds, so the shape is indistinguishable, filed it as ?/N/A. Both types expected during the fading stage.
I have also updated the eclipse type table. I have removed the Broad-U/N/A type, as it appears to be the same as U/N/A, measured eclipse widths – the differences appear to be insignificant. I am also beginning to suspect that U/N/A and V/N/A, and U/L/S and V/L/S represent the same events, except that V-shaped counterparts simply exhibit more flickering during the minima or it is simply a chance alignment of measurement points that produce the V shape. I will leave them as separate types for now, but they are probably candidates for merger.
This data also uses new calibration files, had to redo everything for -15C Moravian C3-61000 main sensor cooling, as the -20C setpoint was pushing the coolers way too much – it’s pretty warm in Sierra del Segura mountains even during the night time. I was waiting to shoot flats for a few weeks. We should have gone for the enhanced cooling option, but we’ll live with -15C for now.
Max
CG Dra Eclipse Zoo. First attempt at systematization. I see 7 eclipse profiles. Some may be artifacts. QROF on the right is whether profile has been seen in Quiescence, Rising, Outburst and Fading stages.
Some comments:
1) What is the difference between Broad-U/N/A and U/N/A profiles? It looks like the width of the “U” shape signifies the size of the accretion disk, i.e. we are seeing larger accretion disk during the rise and the fade, and smaller disk during the quiescence. Could as well be a flickering artifact, i.e. this is a single profile type.
2) U/L/S profile is expected during the outburst and fading stages, with bright accretion disk and relatively dim “bright” spot with the lack of the orbital hump.
3) Why we see V/N/A profiles during outbursts? The light curve is supposed to be dominated by the accretion disk, and here we see bright spot during the outburst in an asymmetric profile, i.e. a mix of a bright spot and accretion disk eclipse. Is this expected for dwarf novae?
4) What is the difference between V/L/S and U/L/S states?
5) V/H/HA and Sharp-V/H/HA are expected near quiescence, as the flux is dominated by the compact bright spot in a highly asymmetric light curve, and we see a sharp eclipse of it.
Max
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CG Dra fading, right after outburst. Good quality data. The eclipse profile is back to V-shape with gentle egress. Mild bright spot hump – I assume the accretion disk is still contributing to the overall brightness immediately after the outburst. Initially I thought that the eclipse profile change may be correlated with outbursts, as EX Dra, for example, shows V-shaped eclipses on the rise and during its outburst stages, but its eclipses become U-shaped on the decline and during the quiescence. But this is not the case with CG Dra, as we have seen very prominent V-shaped eclipse with pronounced bright spot orbital hump on May 28th. My quiescence eclipse profile folder contains a wide variety of V and U shapes.
Max
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CG Dra in outburst. Good quality data today with two eclipses visible. Eclipse profiles are now narrower, some asymmetricity, but not as pronounced as before. The bright spot orbital hump is barely visible, if at all. I assume the accretion disk is now fully lit in the outburst and is now as bright as the bright spot itself, so we do not see a pronounced ingress orbital hump anymore, and the profile appears to be corresponding to the eclipse of the disk, somewhat similar to that during the outburst of June 11th.
Max
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Poor seeing, but interesting data nevertheless. CG Dra on the rise. Broad U-shaped eclipse, profile similar to that in quiescence 2 days ago. I guess the broad component is the disc. Egress still at a lower magnitude than ingress, so bright spot still observable. Although the eclipse depth is about the same, the profile is different from the eclipse of, say, May 28th at quiescence where we saw a bright spot followed by a V-shaped dip to ~17.1 mag. Does this mean the bright spot changed its position and is now eclipsed for a longer duration?
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Thank you, Jeremy. This makes sense. I have submitted all the data.
CG Dra has an interesting curve at quiescence today. Assuming I interpret this correctly, the bright spot ingress begins at 59747.95, but then it gets temporarily dimmed by ~ 0.1 mag at 59747.99, then returns back to the normal brightness, followed by the “main” eclipse event at 59748.00, which is, I assume the eclipse of the accretion disk and/or the bright spot. What is also interesting is the brief ~ 0.1 mag dimming at 59748.06 after the egress, although this could be an artifact. I assume the dips are flickering events.
Max
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Clouds tonight. Not sure if data of this quality should be submitted to AAVSO/BAA VSS – please advise.
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Fading. Not very good sky conditions.
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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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