150 replies to this topic

[Airship]

Wow, this could get interesting. The timing could be very bad for me as this tends to be a very cloudy time of year. I was waiting to hear if anyone would detect any meaningful changes in the spectra. I hate to read too much in the light curve, but the approaching minimum is a tad elevated from the previous minimum. That’s the tricky bit with cataclysmic variables, you never know when they are going to erupt.

 

Neat stuff.

[robin_astro]

from a German observatory '... the first signs that the nova is about to erupt' 

 

https://www.tls-taut...eiben-wachsam-2

Or possibly not ?  A similar short term flare event was seen in amateur spectra in November last year. See the AAS research note published this week.

https://iopscience.i...515-5172/adb425

 

It is possible these events may in fact be relatively common during the low state but are missed due to the low cadence of observations. 

 

Cheers

Robin

[Airship]

Yeah... you know T CrB is going to keep us guessing. That's part of the fun! 😀

[Airship]

A real quickie update as I was able to add a set of observations from this morning that I thought was interesting given the recent discussion of new spectral data...

 

 

The data suggests that we are crossing the current midpoint minimum and there's no indication of a sudden change in brightness in the green channel, however, here does appear to be a gradual brightening of the overall trend with the current midpoint minimum being about 0.2 magnitudes brighter than the previous midpoint minimum. It will be interesting to see if this trend continues across the next maximum. I also want to go back and map where the spectral emissions were observed on both the time-order and phase diagrams to see if there are any features in this data that correlated to the appearance of the emission lines in the green channel data. I could also go back and check the blue and red channels, though I have never done any work with the Tri-R and Tri-B data sets before.

 

Further though is necessary...

 

Edited by Airship, 14 February 2025 - 10:36 PM.

[StupendousMan]

Thank you for the frequent updates!   I'm looking forward to the time when the skies over Rochester become clear again ....

[italic]

This came up on ATel today: https://www.astronom...org/?read=17041

[robin_astro]

This came up on ATel today: https://www.astronom...org/?read=17041

The spectrum from the ARAS database taken on 7th of February they refer to is mine, though I have no connection with the team and I am sceptical about any predictions of TCrB base on accretion rate which varies continuously  in all timescales. (If this was my ATel I would definitely be putting a question mark at the end of the title  )

 

There are actually high resolution H alpha spectra close to all  three dates in ARAS database.

https://aras-databas...abase/tcrb.html

 

 

 

Mine showing the increase in emission is in black.  We do urgently need more spectra though and unfortunately I and other ARAS members  have been clouded out since.

 

Cheers

Robin 

Edited by robin_astro, 16 February 2025 - 07:36 AM.

[robin_astro]

 I am sceptical about any predictions of TCrB base on accretion rate which varies continuously  in all timescales. 

For example here is a spectrum in the ARAS database from 2021 when it was in a continuous high state which shows the same H alpha intensity as my Feb 7th spectrum

 

 

Though of course it could prove me wrong and blow tonight !

 

Cheers

Robin

[Gvs]

T Coronae Borealis (TCrB) is a fascinating "recurrent nova," a star system known to erupt in spectacular bursts of light, and the most recent prediction suggested it should have gone nova in 2025 or 2026. However, as of today (February 21st, 2025), it hasn't happened, and the key lies in understanding the behavior of the system. T CrB is essentially a pair of stars: a red giant star shedding material onto a compact star called a white dwarf. When enough of this material piles up on the white dwarf, it triggers a thermonuclear explosion—the nova. It's a bit like a cosmic pressure cooker, slowly building up until it explodes. The key is in accurately predicting the temperature rise on the hot star before the outburst.

 

The exact timing of these eruptions is incredibly sensitive to several factors, but is largely based on past cyclical activity. The first is the rate at which material is flowing from the red giant to the white dwarf. Since the system had a short hard-flare event near the end of 2024, we can expect an outburst from T CrB again. Since the previous 2 eruptions occurred around 80 years apart, it is not outside of expectations for it to occur in 2026 or beyond. Even the recent hard flare event may indicate that it has only begun its pre-nova period. The flare may be because material has just begun to flow more regularly from the red giant, which can cause rapid increases in temperature. Also, as the matter has been captured by the hot white dwarf, UV energy increases. So again, even if 2025 was a reasonable "expected" date, it's not a guarantee.

 

Despite the uncertainty, scientists are actively studying the system using multiple techniques, including spectroscopy in the infrared and visual spectrum. Although predictions can be made about the timing of the next eruption, there will be greater observation and more research conducted as more material accretes and is ejected by the white dwarf. All of this means T CrB still remains an excellent source for study, and predictions can be re-evaluated.

 

Additional info can be found in this Arxiv paper.

 

You will also find an astro photo taken on Feb 2nd, 2025 at 5:10 CST with an AT80EDT 5 min exposure using a ZWO ASI2600 DUO at 100 gain.  If anyone would like to use it as a reference.

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[robin_astro]

 the most recent prediction suggested it should have gone nova in 2025 or 2026. However, as of today (February 21st, 2025), it hasn't happened,

err... it is only the beginning of 2025.

 

Is this an AI summary ?

[robin_astro]

 

Additional info can be found in this Arxiv paper.

 

 

That paper (sensibly) makes no prediction about when the next eruption might occur because we do not know what observables there are immediately prior to the event. (In fact there is a case to be made that the eruption is perhaps more likely to occur during quiescent periods as  the accreted surface material has to "settle" to reach the critical conditions required and this may be prevented from happening while active accretion is ongoing)

 

The short answer is we cannot predict with any degree of accuracy when it will occur. To quote one professional astronomer

 

"It's the hype that's around  reading chicken entrails and "predicting the unpredictable" that's tapping into the community, you'd almost think that the scientific community has adopted  astrology."

Edited by robin_astro, 21 February 2025 - 12:51 PM.

[yuzameh]

As always there is no prediction whatsoever possible except for taking the time difference between the 1846 outburst and the 1946 outburst and adding it to the date of the 1946 outburst which gives early November 2025.

 

There, however, is not a single outbursting object that outbursts consequent to accretion from a companion upon a white dwarf, of whatever variety of companion, that is periodic, let alone clockwork.  Not one.

 

At best they have timescales, though even within these timescales they can miss an outburst altogether.

 

RS Ophiuchi is the most similar object known except its timescale is much shorter.  Its timescale has a wide scatter and also some gaps when it should have gone off which in more recent times may not have simply been because the outburst was missed due to it being too close to the Sun.

 

Further, the 1700s outburst is feasible but not independently confirmed (nor rigorously identified as the same object for that matter) and the 1200s "outburst" isn't really even hearsay, it's at best myth basedo on straw pulling.  It certainly ain't science.  It's somewhat reminiscent of that one reported about a similary century monk who ostensibly saw something hit the Moon which has even had a candidate Lunar crater predicted but which can never be proven no matter how much flogging that particular dead horse is given.  One could posit accidental inclusion of Fly Agaric in the mushrooms they had in the fish stew that day.

[Gvs]

err... it is only the beginning of 2025.

 

Is this an AI summary ?

An AI answer would have actually stated something along the following lines:

 

Pre-Outburst Activity and Orbital Modulation: Combining all paper, Fekel et al. (2000) and Teyssier et al. (2025) emphasizes T CrB as a symbiotic system exhibiting both orbital modulation and irregular activity increases. With orbital data, Fekel et al. (2000) provides key parameter insights into the red giant. With high cadence spectroscopy, Teyssier et al. (2025) highlights the role of short flares preceding the outburst. The analysis also shows the complexity of the UV Flash interactions described by Shore et al. (1996) and Munari (2024), but it is also related to changes in the central X-ray origin, in accordance to the Starrfield et al. (1990) paper. While the simulations have not ejected any matter for most composition parameters, Starrfield (2025) does expect detectable 22Na gamma decay, and infrared 31P emissions.

Light Curve Features and Accretion: The light curve presented in this figure shows the long period (227 days) of M giant behavior, with a relatively stable magnitude, and the short flares highlighted by Teyssier 2025, possibly due to the variable mass accretion (Munari et al. (2016), Luna et al. (2020)). This can be interpreted as the M giant filling its Roche lobe (Fekel 2000, Iben & Tutukov 1996). The shape of the observed short flares suggest a partial eclipse of the emission region, and is due to high electron density, making it difficult for [O III] gamma decay to occur during that time.

Outburst Timing and Composition Implications: Given the recent detection of a hard-short flare, in addition to continued rapid-mass growth of the White Dwarf and subsequent type I SN outburst, Starrfield et al. (2025) suggests that we are close to the SN explosion. In addition to supporting continued infrared spectroscopy, there also needs to be better modeling. We also have a rare opportunity to observe the nucleosynthesis of the ejected components, and better determine carbon and oxygen compositions, and confirm/ reject ONe results.

 

Now I included the date, because we were all expecting this to happen last year, and wanted to ensure that the attached images where clearly referenced.

[Hd209458]

I do still maintain the prediction that the outburst will occur around March 27 or November 10 2025 (or later in 2026):

https://ui.adsabs.ha.....272S/abstract

[goodricke1]

Maybe it went off 20 years ago when nobody was looking...

[yuzameh]

Maybe it went off 20 years ago when nobody was looking...

Ah, but t'is not the case!

 

The BAA Variable Star Section at least has been following it for decades, back to at least the Sixties, and indeed the visual estimates they have were good enough to readily detect the orbital period and signature upon the folded lightcurve phase plot, and notice when that disappeared and stayed in the highstate, and when it left that highstate.

 

On the other hand you may be quite right, as that was roughly when the roughly decade long highstate started and for all we know THAT was the current outburst.  GK Per (remnant of Nova Persei 1901) did something similar a few years ago or so: every few to five years GK Per has a belch of a few mags which lasts some while (month or so if I remember rightly).  One or two events back it missed a go but did go throw a teasing period of being "excited" with minor brightenings and flickerings as if it was getting ready to go boom (check this, I'm using memory).

 

As for the early Nov 2025 prediction, yep that's exactly what you get if you use the gap between the two known outbursts.  Munari in 2024 also published such a date, he based it on the orbital cycles and the whole number of such between the 1846 and 1946 date which seemed to occur at the exact same phase in the cycle apparently, but in practical terms this is just like saying the time gap in days between the two and also has to assume a fixed orbital period pre and post the 1946 outburst (the period, when detectable, has been quite stable since then).

 

Yeah, I wanna see it too.  But as they say in business, yah've gorra manage yer expectations.  No need for pessimism nor optimism, just try and throw a little realism on it, which is admittedly difficult in this instance due to lack of specific object data, but when extended to the generality DNe CNe and RNe do NOT have PERIODIC outbursts, they have TIMESCALE ones.

 

Much sloppy press and a professional paper noting a dip that is not only unlikely to be real but has only one source and thus no independent confirmation.  Listen to anything Munari says, either in a paper or via an ATEL, and you'll be a lot more informed, he and his team of professionals have spectroscopically and photometrically monitored SyNe, Symbiotic Stars and RNe for decades and published many a data led paper thereupon.

[yuzameh]

PS RNe means Recurrent Novae - apparently it can also mean Reflection Nebulae.  At a stretch of the defintions and most certainly of the imagination maybe some aspects of R Aqr could be called an RNe with an RNe (though I think it's mostly HII emission nebulosity in reality and R Aqr is a SyNe if anything, a past symbiotic nova: stars can be SyNe and symbiotic stars both, the former has to (have) be(en) the latter kind of by default).

 

Look at the piccy in your Burnham's (R jr not S.W.) or the pedia of the wiki entry.  Apparently the R Aqr nebula is Cederblad 211.

[Airship]

Latest summary of my Seestar observations of T CrB. These span from 3/16/2024 through 2/24/2025, closing in on one full year!

 

 

The data on the current phase shows a gradual overall brightening of the T CrB system. It will be interesting to see if this continues over the approaching maximum. I am looking forward to getting two compete cycles of data to work with (assuming the white dwarf doesn't erupt before we get there).

 

[yuzameh]

Noting the potential rise in min mag and assuming it's not a result of looking to another horizon or differing altitude air mass issues or whatever, and noting that since you increased your observation rate the data has become quite noisy interday and it is not clear if this is real or artefact of circumstance (not saying you're doing anything wrong, circumstances vary between seasons and you used to look less frequently), remember that the orbital signature disappeared during the decade or so long high state and that may simply be happening again.  I haven't checked visual archives back to 2000 to see if there was a gradual decrease in amplitude prior to the high state, though I think the amplitude increased over a cycle or two once the high state was over.

 

Doesn't mean it won't blow though, might even have done it now for all I know, as I can't look because we've been visited by that bloke Walter Wal Cloud again - actually he's more like an unwelcome guest who doesn't know when to leave.

[WillR]

Maybe it went off 20 years ago when nobody was looking...

Yazumeh, Goodricke1 is having a little joke. Your post has a typo. You listed eruptions as 1846 and 1946, not 1866 and 1946.

[Alexander Repnoy]

In general, we are ready. By the way, there are two days left until the end of February. If T CrB flares up these days, it could be a rare case of it flaring up twice in a row in the same month. But although such a possibility exists, it is very small. Most likely it will flare up in the new month, no matter which one. That is, it will not be the case that a Northern Corona T outbreak will occur in the same month (February) over the past almost 80 years.

[pbealo]

In general, we are ready. By the way, there are two days left until the end of February. If T CrB flares up these days, it could be a rare case of it flaring up twice in a row in the same month. But although such a possibility exists, it is very small. Most likely it will flare up in the new month, no matter which one. That is, it will not be the case that a Northern Corona T outbreak will occur in the same month (February) over the past almost 80 years.

Probably 1 chance is 12!!

[Alexander Repnoy]

While we are all waiting for an outbreak of T CrB, I found an interesting table. As you know, in our Milky Way galaxy, 10 re-new stars are known. So here it is. According to this table, in addition to the T Northern Corona flare, we are now on the verge of another T Pyx (Compass) flare and V394 Cor Aus (Southern Corona) flare. That is, outbreaks of these repeated novae may also occur in the near future!

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Edited by Alexander Repnoy, 28 February 2025 - 01:04 PM.

[Redbetter]

Probably 1 chance is 12!!

Closer to 1 in 13 on average...but the period under consideration makes all the difference.

 

At the time the post you responded to was made (~26 Feb and about halfway through the day UT from what I see) the chances were about 2.5 out of the 308.5 days remaining in the year.  (1 in 123.4)  That chance will of course become zero for the year in a few hours from the present.  However, there is no guarantee that it will go off in 2025--or even by 2026.  We can only make guesses assigning probability without having any real statistics on the variability of the period or how it might vary around some average.

 

On average the chance of it falling in February it is closer to 28 out of 365, but leap days complicate that, especially since they don't fall every 4 years, skipping one each century, except when the year is divisible by 400 which is also a leap year (as in 2000).  So over the long haul February has 28.242 days and a year is 365.242 days.   So 28.242/365.242 which is 1 in ~12.93

 

The reality is that the probability is increasing somewhat each day until the next eruption (each day that it hasn't gone off increasingly the likelihood compared to the day before and so on.)  However, since we don't know the true long term average or its typical variability/distribution we don't know how much this is increasing each day.  

 

Consider the flip side:  after it goes off, the chances for a subsequent eruption drop to zero for decades, but at some point there is a very small potential for another nova, and it grows each year and subsequent year, until it erupts again.

[Airship]

We just ended another little stretch of early morning observing opportunities. We seem to get a break in the clouds for an hour or so between midnight and dawn. I usually wake up for a bit about this time and take a peek outside. If it looks clear I grab the Seestar S30 and grab a quick image set. 20x10sec subs is plenty, and I usually grab 60x10sec subs if the clouds cooperate. The figures below summarize my Seestar observations from 3/16/2024 through 3/3/2025.

 

 

Enjoy!