CG Dra: a VSS campaign

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  • #611069
    Maxim Usatov
    Participant

    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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    #611071
    Jeremy Shears
    Participant

    Probably flickering, as you suggest Max. All very interesting

    #611077
    Maxim Usatov
    Participant

    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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    #611104
    Maxim Usatov
    Participant

    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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    #611106
    Jeremy Shears
    Participant

    Great stuff, Max.

    #611143
    Maxim Usatov
    Participant

    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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    #611151
    Maxim Usatov
    Participant

    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

    • This reply was modified 2 days, 10 hours ago by Maxim Usatov.
    #611155
    Maxim Usatov
    Participant

    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

    #611160
    Maxim Usatov
    Participant

    CG Dra in quiescence. Looks like a U/N/A type eclipse of accretion disk and a bright spot.

    Max

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