CG Dra: a VSS campaign

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  • #611811
    Jeremy Shears
    Participant

    I see the dilemma, Max (also shows rage pitfalls CV observers can get into with less than ideal data). If you can confidently and consistently compensate that would be the way to go (sorry!). In any case, it would be important to identify those eclipses where there is some kind of uncertainty in assignment of type.

    #611840
    Maxim Usatov
    Participant

    Yep, I’ll use question mark.

    Eclipses No(s): 63, 64, 65 (next day)
    State: Quiescence
    Profiles: U/N/A, U/N/A, V/N/A

    • This reply was modified 3 days, 10 hours ago by Maxim Usatov.
    #611844
    Jeremy Shears
    Participant

    Looks slightly shallower, as expected, Max

    #611854
    Maxim Usatov
    Participant

    Eclipses No(s): 66
    State: Rising

    Another surprise from CG Draconis – a post-egress hump (PEH) during the very early rising stage of the outburst, combined with high orbital hump amplitude – a U/H/PEH type profile, seen first. There was an interruption in data right after the PEH peak, but we can still see it was rather narrow.

    At this state the white dwarf’s accretion disk must still be dim and cold, or at least partially hot, as the bright spot is prominent, peaking at phase 0.85 when it’s directly facing Earth. Its amplitude almost reaches 0.2 mag, making it a “high” hump in my classification.

    What normally follows is an asymmetric, slower egress, however, this time we have an opposite case, I think, caused by a PEH. peaking at approximately phase 1.1. This phase coincides with the emergence of the bright spot on the other side of the eclipse. This could signify that the diameter of the bright spot is bigger than the thickness of the accretion disk, or, perhaps, that the disk is unusually optically thin at this early stage of the outburst.

    It would be really interesting to have some input on these speculations. Although I have only recorded two eclipses during the rising stage of the CG Dra outburst, I would expect asymmetric egress, with the bright spot concealed by the disk on the other side of the eclipse.

    If the disk is so unusually transparent tonight, what suddenly caused it? We have seen no PEHs during previous eclipses after the bright outburst. If the bright spot is unusually large now, extending beyond the accretion disk, which is supported by the absence of the standstill on the egress, then does this signify an increased accretion rate? If so, what has suddenly caused it? We have seen that there was no PEH at all yesterday – the eclipse was asymmetric.

    The more data is being collected, the more questions I have.

    Max

    Attachments:
    #611856
    Maxim Usatov
    Participant

    Addendum:

    I have found a V-shaped counterpart to this U/H/PEH eclipse, observed once at quiescence on May 28. I have called it Sharp-V/H/HA back then – high orbital hump, highly asymmetric. (See attachment, tonight’s U/H/PEH on the left, the Sharp-V one on the right.) Looking at the phase plots, I see both profiles are very similar, so I will rename the May 28 profile to V/H/PEH.

    Max

    #611858
    Jeremy Shears
    Participant

    That is a dramatic eclipse Max! Seems to be enhanced by the preceding hump.

    #611867
    Maxim Usatov
    Participant

    Eclipses No(s): 67, 68
    State: Rising

    U/N?/A + U/L/S eclipse. Two different profiles on the same night, although there is no clear cut line where eclipse becomes asymmetric in my system. The latter eclipse is still slightly asymmetric.

    Max

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    #611875
    Jeremy Shears
    Participant

    Interesting to see them superposed on the brightening trend line

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