Thomas,

Thanks. That's very interesting.

I think the fact that the comet is brightening again and that there are
no biased astrometric residuals is fairly strong evidence that this
comet is not dead yet!

Nick.

On 10/07/2024 12:59, Thomas Lehmann - t.lehmann at mailbox.org (via
baa-comet list) wrote:
> Jeremy, thanks for the link to this very interesting paper.
>
> Nick, I certainly agree with you regarding the brightness evolution of the
> comet. I am attaching a plot containing measurements by myself using different
> telescopes and some data of S. Fritsche (indicated by the telescope
> identifier TS1006D). Those are magnitudes derived from green filtered images
> using a fixed aperture diameter of 50000km. I have added two model light curves,
> one derived from data until April 1st and the other from recent observations.
> The similarity of both curves - despite the difference in the activity
> parameter - indicates that the comet is slowly recovering and not too far from
> the evolution it has shown early this year. It does not look like an
> disintegrating comet at present.
>
> Regarding the phase angle effect. It is obvious that there is a brightening
> in mid-April at the time of lowest phase angle. But the brightness decrease
> after that time is much larger and steeper than before. Therefore I believe
> that the phase angle affect is not the major source of the brightness dip.
> In addition the projection effect of changing tail orientation is also
> not strong enough to account for the dip. I have measured the comet including
> the tail and obtained a boost in total comet brightness of only about 0.3mag by
> the end of May/beginning of July (with respect to my large aperture photometry
> results as published at COBS).
>
> Maybe the observed strange lightcurve reflects variation in the size of
> the active region on the nucleus or changing geometry with respect
> to the solar radiation, e.g. precession (especially if one assumes a largely
> non-spherical body).
>
> Anyway, an interesting object and only by further observations we might get
> new clues about what is going on there ...
>
> Thomas