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However, the 10.17ish from that paper seems to be just the contribution from the Red Giant star in the binary, and what we measure should be the combined flux from the entire binary system including the accretion disk. At the moment, from the AAVSO light curves, I would think a Vmag of 9.8 (fluctuating between 9.75 and 9.85 perhaps) should be about right. If we assume those values and no variability of the donor on short timescales (hours), if my math is right, it would mean that the accretion disk alone, without the red giant donar star, fluctuates between roughly 11.0 mag (V) and 11.3 mag (V) on short timescales, right?
I have now used my little tool to evaluate the brightness of T CrB in real-time with a Seestar S50 smart telescope (and sound an alarm to wake me up in case of an outburst!) for more than 20 clear nights, some with rather challenging intermittend clouds) and I’m now confident enough to recommend its use by others.
https://github.com/Bikeman/SeestarPhotometricWatchdog
I still need to correct many typos in the documentation files README.md and Adv_Documentation.md (which were written in a frenzy to outrun T CrB going nova…) but the scripts themselves are stable.
I’m still looking for people who want to give this a try with the newer Seestar S30 product. If someone wants to port this to Windows, that would also be most welcome (it’s currently intended to be hosted on a Raspberry Pi or other Linux host).
CS
HBEIs the Symbiotic Recurrent Nova T CrB Late? Recent Photometric Evolution and Comparison with Past Pre-Outburst Behaviour
I hoped they may stick their necks on in the section 4.3 “when will T CrB erupt?”. They observe that “Recent photometric and spectroscopic observations indicate that the system is returning to a high-accretion state. Given this, an eruption may be imminent, even without distinct precursors”. So, as ever, we shall just have to keep on watching as there might be no warning.
Ulisse Munari et al. have published a pretty comprehensive analysis of T CrB’s accretion history in this Astronomy & Astrophysics preprint:
https://arxiv.org/abs/2507.23323They point out that its superactive phase from 2015 to 2023 was actually not quite as active as the equivalent phase that preceded the 1946 eruption. They note that the increased accretion since May 2024 is making up for this deficit.
My observations in Johnson B filter so far since August 2023.
Attachments:
So when will the eruption occur ? I am very impatient.
Many thanks.Kwong Man
That will be when sufficient matter has accumulated on the surface of the white dwarf to trigger a thermonuclear runaway. Your guess is as good as mine when that will be.
Right now my little Seestar S50 sees it at 9.5 mag in the green filter. I had set this as the alarm value in my automatic watchdog script so literally an alarm was sounding, but currently it stays stable at 9.5 mag, so no cigar quite yet. I guess I’ll have to raise (well, lower) the magnitude bar a bit to avoid false alarms.
Still, 9.5 mag is a bit on the bright side of what I’ve seen so far. Let’s say it’s probably not the time to get sloppy about observing this one!!
Good to hear you are continuing to monitor T CrB with your Seestar, Heinz-Bernd. As you say, now is not the time to blink!
A comparison of the current spectrum with one in the low state March 2024
https://britastro.org/observations/observation.php?id=20250810_221150_5f858c960a245997Cheers
RobinAn ApJ preprint on ArXiv today on “Elemental and Isotopic Yields from T Coronae Borealis: Predictions and Uncertainties” discusses various models of nucleosynthesis in novae, suggesting which isotopic observations during its next eruption will enable the correct model to be diagnosed.
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