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 1 month, 3 weeks 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

    Attachments:
    #611875
    Jeremy Shears
    Participant

    Interesting to see them superposed on the brightening trend line

    #611918
    Maxim Usatov
    Participant

    Eclipses No(s): 69, 70
    State: Fading
    Poor data quality. I assume poor transparency and occasional clouds, but difficult to say exactly why remotely.

    Attachments:
    #611928
    Jeremy Shears
    Participant

    Yes, probably poor transparency and moonlight interference, Max.

    #612074
    Maxim Usatov
    Participant

    Back from the vacation. The telescope was collecting data, 2243 observations have been made for period August 14 to 23.

    August 14, 2022, State: Quiescence
    Eclipse No. 71, Profile: V/N/A

    August 15, 2022, State: Quiescence
    Eclipse No. 72, Profile: V/N/A
    Eclipse No. 73, Profile: V?/N/A

    August 17, 2022, State: Quiescence
    Eclipse No. 74, Profile: ?/H/? – Intermittent data.

    August 18, 2022, State: Quiescence
    Eclipse No. 75, Profile: U/N/A
    Eclipse No. 76, Profile: U?/N/A

    August 19, 2022, State: Rising
    Eclipse No. 77, Profile: U/L/S – Accretion disk becomes bright.

    August 20, 2022, State: Outburst
    Eclipse No. 78, Profile: U/L?/S

    August 21, 2022, State: Outburst
    Eclipse No. 79, Profile: U/L/PEH
    Eclipse No. 80, Profile: U/L/PEH
    Post-Egress Humps developed at the peak of the outburst, peaking at phase ~ 1.125.

    August 22, 2022, State: Fading
    Eclipse No. 81, Profile: U/L/S (brightening at a late phase due to the overall fading)

    August 23, 2022, State: Fading
    Eclipse No. 82, Profile: U/L/S (brightening at a late phase due to the overall fading)

    Max

    #612083
    Jeremy Shears
    Participant

    Welcome back, Max. I was getting worried! Good to see that data have been collected in the meantime

    #612084
    Maxim Usatov
    Participant

    Thanks, Jeremy! Good test for the autonomous operation. Looks like our scripts are now handling most of the software/hardware random bugs. At this point, I simply define the object, area of the sky and the A1 telescope wakes up, cools down, homes the mount, centers the focuser, slews, begins the imaging plan when the object is visible, etc – once the roof opens. The server in London data center pulls all the FITS in the morning, does photometry and I get e-mails with BAA/AAVSO report files. No interaction required whatsoever except for to produce the charts. Hopefully just a little more effort with the web UI interface and we can begin serving time for BAA on it.

    I see that for some reason the most interesting curve from August 21 with PEHs has failed to upload. I’m attaching it here.

    Max

    • This reply was modified 1 month, 1 week ago by Maxim Usatov.
    Attachments:
    #612087
    Jeremy Shears
    Participant

    Impressive set up, Max. Looks very reliable indeed.

    #612149
    Maxim Usatov
    Participant

    Very intermittent data will be uploaded during the next few days, won’t post charts.
    Max

    Attachments:
    #612177
    Stewart John Bean
    Participant

    I had a look at the AAVSO curve, dominated by Max’s data of course (impressive). The last period 2459700 to present reminds me of an ER UMa star in that there are two bright outbursts with a series of smaller ones between. The brighter outbursts seem to be 70 days apart.

    There are no TESS observations unfortunately.

    Ive added it to my SLOOH watch list for Canary.

    Stewart

    #612179
    Stewart John Bean
    Participant

    With a screen shot

    Attachments:
    #612182
    Maxim Usatov
    Participant

    Thank you, Stewart.

    Eclipses No(s): 83
    State: Quiescence
    Got some poor quality data despite the clouds, U?/N?/A profile.

    Attachments:
    #612185
    Jeremy Shears
    Participant

    Nice to see you continuing despite the inclement wx, Max.

    #612202
    Maxim Usatov
    Participant

    Thank you, Jeremy! The mystery of CG Draconis has to be solved!

    Eclipses No(s): 84, 85
    State: Quiescence
    U/N/A + ?/N/? eclipses, typical for quiescence. Post-egress hump peaking at phase ~ 1.2 on the first eclipse, coinciding with the reappearance of the bright spot on the other side of the eclipse.

    Attachments:
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