Nick,
I am not sure if you have had the attached astrometry of C/2019Y4 from
me. These are all measures taken when the individual components has
faded and I was reporting only as C/2019Y4 and not as component B.
If you have had these from me sorry for sending them again.
Denis

    CK19Y040 KC2020 04 22.91287 05 50 07.27 +63 26 23.1          15.9 R
     I81
     CK19Y040 KC2020 04 22.91943 05 50 05.66 +63 26 14.3          15.9 R
      I81
     CK19Y040 KC2020 04 22.92744 05 50 03.61 +63 26 03.6          15.9 R
      I81
     CK19Y040 KC2020 04 23.92956 05 45 50.68 +63 03 40.3          15.9 R
      I81
     CK19Y040 KC2020 04 23.93575 05 45 49.13 +63 03 32.1          15.9 R
      I81
     CK19Y040 KC2020 04 23.94195 05 45 47.62 +63 03 23.4          15.9 R
      I81
     CK19Y040 KC2020 04 24.93205 05 41 42.24 +62 40 37.4          16.0 R
      I81
     CK19Y040 KC2020 04 24.93569 05 41 41.35 +62 40 32.2          15.9 R
      I81
     CK19Y040 KC2020 04 24.93933 05 41 40.50 +62 40 27.1          15.9 R
      I81
     CK19Y040 KC2020 04 26.94884 05 33 34.04 +61 52 08.2          16.0 R
      I81
    CK19Y040 KC2020 05 04.98856 05 02 21.94 +58 01 28.3          15.1 R
     I81
     CK19Y040 KC2020 05 04.99217 05 02 21.07 +58 01 20.6          15.2 R
      I81
     CK19Y040 KC2020 05 04.99578 05 02 20.26 +58 01 13.2          15.2 R
      I81
     CK19Y040 KC2020 05 05.97184 04 58 32.86 +57 27 32.9          14.8 R
      I81
     CK19Y040 KC2020 05 05.97550 04 58 32.01 +57 27 25.1          14.8 R
      I81
     CK19Y040 KC2020 05 05.98062 04 58 30.84 +57 27 14.6          14.8 R
      I81
     CK19Y040  C2020 05 06.96532 04 54 40.08 +56 51 32.4          14.7 R
      I81
     CK19Y040  C2020 05 06.97045 04 54 38.88 +56 51 20.8          14.6 R
      I81
     CK19Y040  C2020 05 06.97484 04 54 37.82 +56 51 10.8          14.6 R
      I81
     CK19Y040  C2020 05 06.97850 04 54 37.01 +56 51 02.3          14.4 R
      I81
    CK19Y040 KC2020 05 10.95352 04 38 44.83 +54 05 02.8          12.7 R
     I81
     CK19Y040 KC2020 05 10.95678 04 38 44.07 +54 04 53.4          13.5 R
      I81
     CK19Y040 KC2020 05 10.97649 04 38 39.31 +54 03 57.6          12.3 R
      I81
     CK19Y040  C2020 05 11.95980 04 34 37.66 +53 16 08.6          12.6 R
      I81
     CK19Y040  C2020 05 11.96125 04 34 37.34 +53 16 04.4          12.6 R
      I81
     CK19Y040  C2020 05 11.96342 04 34 36.75 +53 15 57.2          12.6 R
      I81
     CK19Y040  C2020 05 11.96632 04 34 36.02 +53 15 49.4          12.8 R
      I81
     CK19Y040  C2020 05 15.01183 04 21 52.49 +50 25 02.2          13.4 R
      I81
     CK19Y040  C2020 05 15.01335 04 21 52.08 +50 24 56.6          13.5 R
      I81
     CK19Y040  C2020 05 15.01524 04 21 51.59 +50 24 48.9          13.4 R
      I81
     CK19Y040  C2020 05 15.01675 04 21 51.25 +50 24 43.7          13.6 R
      I81
     CK19Y040  C2020 05 15.01863 04 21 50.77 +50 24 36.3          13.5 R
      I81

On 19/05/2020 21:05, Nick James wrote:
> Richard,
>
> I think that your image fairly conclusively shows that this has become
> an ex-comet! Your analysis is interesting although separation at 100 m/s
> would imply a very violent fragmentation.
>
> Astrometric residuals are attached for the observations that I have
> access to. I'm not sure they tell us much at this stage. These are all
> nominally for component B. No NGFs have been included and the orbit has
> a mean residual of 0".47 using observations from April 9 (when fragment
> B was first measurable) to May 9 (shortly after the outburst that
> probably destroyed it). Measurements after that date have not been
> included in the orbit solution and the centroids are probably biased in
> any case.
>
> If anyone would like to submit astrometry of component B which is not in
> this list please do so and I'll run the solution again.
>
> Nick.
>
>
> On 19/05/2020 15:36, Richard Miles - rmiles.btee at btinternet.com (via
> baa-comet list) wrote:
>> Hopefully the attached demonstrates that the comet has now disintegrated.
>>
>> Some thin cloud was around last night and it never turned into a
>> properly clear night but as the target was circumpolar at the time I
>> was still able to follow it for a couple of hours as it tracked along
>> my northern horizon some 26 degrees from the Sun.
>>
>> We can now see the result of the outburst on May 8. Although Component
>> B, the most massive part of the comet, appeared to have survived that
>> outburst, this was an illusion as we now know it disintegrated and
>> although we could see a bright pseudonucleus at that location on May
>> 9-16, we were just witnessing the expanding debris cloud. Of much more
>> interest is what happened to the solid body of B. It appears that
>> there was an explosive event on May 8 that blew a considerable mass of
>> material sunwards at speeds of 80-100 m/s.
>>
>> The ejected material comprised a leading body with debris trailing
>> behind it (see my email of May 16). The leading body disintegrated as
>> a consequence of this energetic event. If  we do astrometry on
>> Component B up until it disappeared, we may see that it was slowed
>> slightly following the outburst - a necessary result of conservation
>> of momentum. So although we measure the separation velocity to be
>> 80-100 m/s, we need to do the astrometry to see how the change in
>> velocity was shared between the two 'fragments'.
>>
>> Richard
>>
>> ----- Original Message ----- From: "Nick James" <ndj@nickdjames.com>
>> To: <baa-comet@simplelists.com>
>> Sent: Sunday, May 17, 2020 7:33 AM
>> Subject: [BAA Comets] C/2019 Y4 on May 16
>>
>>
>>> I think we can safely say that C/2019 Y4 will soon be redesignated
>>> D/2019 Y4. It faded another 0.5 magnitudes from May 15.9 to 16.9 and
>>> there is no photocentre left for astrometry. All that we see now is two
>>> fading trails of debris.
>>>
>>> It is a very challenging target now as it dives towards the northern
>>> horizon but please keep imaging it if you can.
>>>
>>> Nick.
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