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Whilst the uncertain eruption of TCrB has become a focus for observation this year, I think the forthcoming periastron of the binary Wolf Rayet star WR140 shouldn’t be neglected. A high-resolution pro-am campaign around the previous periastron in 2016 December resulted in improved orbital elements with an estimate of 2024 November 22 for the next. (‘The orbit and stellar masses of the archetype colliding-wind binary WR 140’ Joshua D Thomas et al, Monthly Notices of the Royal Astronomical Society, Volume 504, Issue 4, July 2021, Pages 5221–5230 https://arxiv.org/abs/2101.10563 ). Regular observations in low resolution during the weeks around periastron should make for a great project, allowing many of the broad emission lines to be monitored for changes:
The flat-topped CIII emission was the focus for observation in 2016 and although I was at the beginning of my spectroscopic journey back then, I managed to observe changes in this line with my Alpy 600:
It would also be interesting to see how well the changes in radial velocity can be observed. And could a relative brightening in the infrared be detectable after periastron, due to dust formation? If I have properly understood the timings from the literature, then the first milestone is reached around now:

Conjunction of the O5 star in front of the Wolf Rayet WC7 star: 2024 July 14
Quadrature (RV of the WC7 star -130 km/sec, O5 star +50 km/sec): 2024 November 11
Periastron: 2024 November 22
Conjunction of the WC7 star in front of the O5 star: 2024 November 30
Quadrature (RV of the WC7 star +30 km/s, O5 star -20 km/sec (observe after 02:00UT)

WR140 will be well placed for evening observation during the crucial time period.
Cheers
Hugh

Thanks for the reminder Hugh !

The periastron previous to that one was also followed in 2008-9 by the same "Convento" pro-am team.
https://ui.adsabs.harvard.edu/abs/2011M ... F/abstract
Here is what happened to the flat topped CIII line as the winds collided
http://www.threehillsobservatory.co.uk/ ... tra_41.htm

It is plotted in the WR star rest frame. You can see the excess emission from the wind collision and the tiny bump in the middle from the O star moving in velocity relative to that as they sweep past each other.

I've not heard if there is any planned organised campaign this time round though

Cheers
Robin

Here is my recent Alpy600 and LhiresIII(2400 ln/mm grat) spectra as well as some photometry I'm submitting to AASVO.
Transformed Mag.'s:


Alpy600 Spectra:


LhiresIII Spectra:


I'll shot photometry on this semi-daily and shot spectra weekly.

James

Here is a LhiresIII spectrum of WR140 centered near the CIV line, shot on 12Sep2024; R=10,729:


James

I think we could expect to see the first blue-shifted excess on the flat-topped CIII emission by October 16th or even earlier, based on what I observed during the last periastron. At the moment the CIII emission is still fairly constant: A heliocentric correction has been applied, and the calibration has then been adjusted based on the interstellar sodium absorption line in the spectra.
Here is the comparison at the full wavelength range: Cheers
Hugh

After three frustrating weeks of cloudy weather here in the southwest UK, it was possible to catch up with the evolution of WR140 as it approaches periastron on November 22nd. The blueshifted emission excess has begun to emerge on the normally flat-topped CIII emission line :
All of the emission lines from the Wolf Rayet star are showing a significant blueshift of the order of 100km/sec, whilst the He II absorption from the O5 companion star shows barely perceptible redshift at this resolution: