154 replies to this topic

[jgraham]

It seems to be cresting, though taking its time. My most recent observations from 3/16 through 8/10...

 

 

The suspense continues...

 

 

 

Edited by jgraham, 11 August 2024 - 06:50 PM.

[jgraham]

My observations suggest that T CrB is still cresting, though taking its sweet old time doing it. This is a summary of my observations through last night...

 

 

We are about to enter a cloudy stretch, so this will be it for me until probably next week.

 

Hang in there!

 

[Redbetter]

The V mag measures are bumping up a little again after a brief dip.  Based on the typical half cycle time, this bright phase should be peaking a little later than it was looking like it might a few nights ago.

 

Less than four weeks to the end of the projection window now.  I will be interested to hear the new projection if it doesn't go off by then.  I have dibs on the Ides of March, 2025 (simply an average of the two prior nova periods.)

[jgraham]

Heh, heh, I just hope it doesn't erupt while it's hidden in the sun's glare later this year. That would be a bummer.

[jgraham]

Okay, now it's just being stubborn. I ordinarily wouldn't post an updated data set this early, but I was able to grab a photometric image last night expecting it to show that T CrB was fading and I would be able to post an update showing that it had crested. Instead, it brightened a tad! A quick check of the V data being reported to the AAVSO shows similar behavior. Not a huge swing, but a little bit of a fading followed by a little bit of brightening. Soooo, if nothing else, T CrB may be getting a bit squirrelly.



The Plot Thickens...

Edited by jgraham, 17 August 2024 - 12:33 PM.

[jgraham]

Against all odds we actually got a bit of clearish skies last night and I was able to grab another decent photometric image of T CrB. Once again it looks like it is cresting with a measured brightness of 9.82, just a tad fainter than the night before and the overall trend line shows that it is turning the corner (again).

 

It is certainly fun to watch!

[Dean Norris]

Here’s my recent visual magnitude estimates of  T Cr B. Estimates made with 10” Newtonian and a 15” Truss Dobsonian.

 

Date    Magnitude

8/5       9.8

8/6       9.8
8/7       9.7
8/8       9.7
8/9       9.7
8/10     9.8
8/11     9.8
8/12     9.9
8/13     9.9
8/15     9.8
8/17     9.8

 

 

Dean

[Rich5567]

Last nights (20/8/24) visual estimate of T CRB with SCT 200mm.

 

20/8/24. JD 2460543.3785 at 21:05 UTC. BAA VSS chart 25.03.  L-2, 10.0Mv .

 

So slightly fainter than previous nights, but nothing unusual. 

Edited by Rich5567, 21 August 2024 - 05:14 AM.

[jgraham]

My latest set of observations up through last night...

 

 

This has been a lot of fun!

 

[RAKing]

A better chart for doing estimates of T CrB in its normal range is X37374DR or X37498BU  (which are the same chart from what I see) with a 1 degree field.  These are what I have used for doing estimates with the AT72EDII and the AT125EDL in the suburbs.  

 

FYI - Each chart that you create on AAVSO will have it's own unique number.  This helps them check accuracy when you submit an estimate to the database.  I have been a member of AAVSO since 2010 and have printed some new charts over the years as they are updated.  I pulled some new charts for T CrB a few years ago, with new numbers, and have been estimating it for the past 13 years.

 

 

I estimated it last night and it was still quiet at 10.1 mag, but I guess it could pop tonight!  

 

Ron

[Rich5567]

My latest estimate:

 

T CRB: chart (BAA 25.03) JD 2560544.4711 (21/8/24) at 23:18 UTC.

 

L-2, 10.0mv.

Edited by Rich5567, 22 August 2024 - 04:32 PM.

[RAKing]

I checked it again late Friday night.

 

T CrB: 2024/08/24 - 0230 UTC  - 10.0 mag.  I used my 1.0 degree AAVSO chart.

 

Ron

[Rich5567]

My latest estimate:

 

T CRB: chart (BAA 25.03) JD 2560547.4014 (24/8/24) at 21:38 UTC.

 

L-2, 10.0mv.

 

No change.

[SNH]

My latest estimate:

 

T CRB: chart (BAA 25.03) JD 2560547.4014 (24/8/24) at 21:38 UTC.

 

L-2, 10.0mv.

 

No change.

Yup, I got V = 10.0 last night using 10x50 binoculars.

 

Scott H.

[jgraham]

Hot off of the Seestar...

 

 

...a summary of my observations from this campaign through this evening (about an hour ago). It's taking its sweet ol' time making the turn, but if you compare current rate of change over the crest with the previous maximum the rate of change is about the same.

 

 

[Redbetter]

It is no surprise the turn is slow if one looks at the overall orbital period and compares to the last several cycles.  The somewhat brighter peak was a bit early and bright relative to the normal half orbital cycle, so it was/is likely to remain there longer before dimming substantially.  The shape of the giant star is likely somewhat complex with an accretion disk figured in, so small amplitude brightening and dimming over short time cycles doesn't seem out of place on either end of the curve.

 

16 nights remaining in the original window.  

[yuzameh]

Hot off of the Seestar...

 

T CrB (3-16 to 8-26-2024)-1j.JPG

 

...a summary of my observations from this campaign through this evening (about an hour ago). It's taking its sweet ol' time making the turn, but if you compare current rate of change over the crest with the previous maximum the rate of change is about the same.

I've been having a read, after all reading on sciency stuff hasn't been quite banned yet nor all facts deemed fake whilst fakery is deemed truth because "someone said so".

 

Which part a variable star's physical cycle leads it to be at maximum, whether an intrinsic or extrinsic one, is not always plainly obvious from just thinking about it in general.  For example, thinking of of ellipsoidal variables as 'egg shaped' for simplicity's sake might make one think that when the pointy end is pointing towards us it will be brighter than when the blunt end is.  However, we measure flux from what is essentially a point source to our instruments (which includes the eyeball), and that's non-linearly related to surface area.

 

Ellipsoidal variables are at maximum light when they are edge on, that is not either the blunt end or the pointy end, so no need for lilliputian conflicts there.

 

A classic lightcurve for such that can be looked up is that for AO Cassiopeiae.  However, that's two massive hot blue stars, both ellipsoidal, pointy ends facing each other.  For interacting binaries where one 'star' is a white dwarf, neutron star (eg LMXB) or black hole the other is often a red giant or larger, but mostly red nevertheless (HMXB is going to be a neutron star and a blue (super)giant).  That means only one star is being seen.

 

Using GAIA DR3 parallax and colours, which makes the thing about 1 kpc distant and absolute G magnitude around -1 we can take the average to modal absolute G magnitude of white dwarfs, including ones in interacting binaries, as about 12 and say that therefore the white dwarf is 13 magnitudes fainter, at least in G.  Well, the red giant (and it has the appropriate colours and absolute magnitude to be such according to GAIA DR3 data) just a bit less than apparent mag 9 in GAIA DR3 G magnitude, which means the white dwarf is around apparent mag 22, so there's no contribution noted from that.

 

However, there's something called the reflection effect.  The hot white dwarf, and in some cases its accretion disc, can cause a hot spot in the atmosphere of the red giant which can amount to about 0.1 in mag brightening.  Simplistically the pointy end should be the point of irridescence as it faces the white dwarf, but due to angular momentum and possibly sometimes magnetic fields this doesn't necessarily hold as rigidly exact and it seems the signal due to reflection effect can be quasi-sinusoidal, that is periodic but at times a bit off, either early or late.

 

Due to the hotspot being UP TO 0.1 magnitude, some potential drift in phase relative to the orbital signature of the ellipsoidal variable, this may be a simple case of them currently being in sync around maximum light for a while and thus giving a bit of a boost (thing sideways on egg with pointy end lit up a bit more than usual).

 

And that could all be a load of drivel.

 

On the other hand, accretion discs can also have their own, different, hotspot, where the stream of matter dragged from the companion star by the white dwarf first comes in contact with the accretion disc (in Polar Cataclysmic Variables there's a strong magnetic field which causes this stream to impinge upon the pole(s) and the hotspot is on the white dwarf, there being no disc to speak of, whereas for hybrid Intermediate Polar CVs, which have that effect as well as still having an accretion disc, likely because the magnetic field strength is not as strong, I've no idea what gives).

 

We can discount that though, as such hotspots are only noted when the white dwarf, plus its accretion disc, and its companion star, often a red dwarf, are of similar brightness which allows the bright hotspot at the accretion node to be visible.

 

Maybe the accretion has increased?  Enhanced accretion equals more reflection effect which can lead to greater mass in the accretion stream which can lead to more friction when it hits the disc which leads to more heat which makes things brighter which increase the reflection effect which heats up more of the red giant's atmosphere which increases mass transfer, until runaway, overloaded accretion disc, dumping of matter directly onto the white dwarf, thermonuclear fusion there, and boom.

 

The problem there is that T CrB has only just returned to normal state after a ten year 'high state', which is easiest explained by enhanced accretion rate upon the disc in that period, sufficient to hide the orbital signature of the ellipsoidal red giant during that longterm event.

 

There is no indication of that in the old data prior to the 1846 outburst, and indeed the claimed dip prior to boom last time is from only one observer so is not confirmed.  Indeed, looking at AAVSO visual data for that time said observer saw nothing but a flat line which means either the ellipsoidal variation was missing or the observer didn't detect it, perpetually self-biasing a "stays the same" measure.  You've seen that happen in this thread so it is not unlikely.  Indeed, for a short period a few years before then there a small bunch from a couple of Europeans who were also taking measures and they have some inherent scatter, rarely agreeing with the lone observer, and even themselves at times, but about the size of the orbital signature.  Anyway, a red giant doesn't get pulled into ellipsoidality by a massive compact companion in just a handful of decades, remember also the 1866 outburst.

 

Finally, in this diatribe, there are the claimed photographic 'magnitudes' denoted as 'blue'.  Johnson B photometric band is not the same as photographic blue, which on survey plates wasn't deliberate, the glass plates had a blue bias inherently it they were to be 'fast' enough for astronomical work.  Also, who knows which plates were used, where they all eastman-kodak or similar, or did the Europeans grow their own.  Further, have you ever looked at scanned images of Harvard or especially Heidelberg patrol plates?  The latter at least have an online interface to view them.  Their quality is all over the place and some are truly abysmal, and not all are to the same limiting magnitude.  POSS I, the original survey in the fifties, has far more quality in its plates, but the derived USNO B magnitudes from those plates are only good to plus or minus half a magnitude, a one magnitude range of error.  Thus how someone can confidently give such a clean blue lightcurve, ironically mirroring the claimed visual lightcurve (there should have been some drift in B-V, a lessening in value) of amplitudes less than the measurable scatter, is a telling question.

 

My personal theory is self aggrandisement overriding objective rigour.  Claiming the evidence for the medieval event as evidence in any way is borderline farcical in my personal view.  Historiographers would likely cringe at the lack of historicity involved in this intepretation.

[yuzameh]

16 nights remaining in the original window.  

No, 46.

Remember he said  April (or some such, I can't remember with his more than one claims, might've been May) plus or minus a time period where the outer range was thus declared September by the journoes.  S&T, Astronomy, NASA, science webnews sites, all repeat the same drivel.

He'll claim accuracy if it goes off in October (well, I was near) or even in 2024, after all it can't be predicted cleanly, plenty of things that go boom are not strictly periodic between booms, even when a 'period' is known, it can rightly be claimed that such is more of a timescale, a very approximate timescale.

The hardcore date predicted being April/May will be conveniently forgotten.  In fact it already has been, the headline for repeat releases of 'reminders' now say September in wording that says it was always going to go off in September, and will do so.

Now, following a slightly upped maximum magnitude, possibly, depending on independent confirmation, if there is also a slightly upped minimum in three to four months (or almost exactly four moonths), maybe it is getting due.  Or maybe not.

The simplest and safest bet, still, is differencing the much independently confirmed outburst dates of 1866 and 1946 and adding that to the 1946 date which gives early Nov 2025 and saying it will be on that date plus or minus two years.  That takes all valid real empirical data and goes for the most simplistic and assumption free route, the only assumption being it follows the pattern of other recurrent events of vaguely similar timescale, both other recurrent novae and some UGWZ variables (eg WZ Sagittae itself, which although having a dwarf companion star has a more similar outburst timescale to well within an order).

There's a point here about how abysmal the more purportedly respected astronomical journalism is.  For a sideways example, in an article in S&T it was stated that Sekanina "published" a prediction of an upcoming bright comet having broken up.  He did not.  He "posted" an article to astro-ph, which is no different from me attaching a pdf on something to this post.  No different in kind, at least, difference in degree of capability and knowledge, yes, he infinitely outstrips my competence and capabilities, be he DID NOT publish in a peer reviewed relevant astronomical venue.  You may feel that is pedantry on my part, but words matter, and we know we have a preconceived idea as to what "published" means in the scientific context.  Granted arxiv are more strict on astro-ph registration and ability to submit a paper nowadays, but they weren't always and I believe the restrictions were not retroactive except in cases of abuse of privilege.

In that case the S&T article also completely forget to mention that after many a forum and maillist pooh-poohed this stating that he had completely forgotten about a phase angle issue which would have occurred/commenced about the time he was claiming for the breakup he then again POSTED another paper to astro-ph debunking the phase angle point with an abstract that read like a three year old churlishly defending themselves when in the wrong.

Meanwhile, since then, observations (you know, facts, not theory and conjecture) have shown the evolution of the comet's lightcurve and shown that the lightcurve profile has evolved both in brightness and temporally as would be expected should such a phase angle even have occurred, and what's more is still brightening, albeit at a lower magnitude trend than originally hoped, rather than fading after a disintegration event would cause.

Two examples of journalism instead of science reporting that has swept through the astronomic and scientific news without any valid reason given the slightest smidgeon of research and data checking would have shown them false.

But remember T CrB will blow up in September, for he has spoken...

Knowing my luck the comet will end up a total dud and T CrB will blow up the same week.  It is strange to almost desire them both to not follow their predictions, as that is the less satisfying scenario, simply due to a personal strong dislike of borderline pseudoscience, at least both predictions are such in my personal opinion.

[Redbetter]

Nope, 16 and shrinking.   The AAVSO announcement he made was 2024.4±0.3 years.  He has until Sept. 12 UTC.    Sept. 13 and beyond is outside the window of the prediction.  If he wanted a wider range, he should have provided one.  

 

It doesn't bother me that articles have simplified it to September for mass consumption.  However, some of us are actually keeping track.   

 

I am curious as to how short the actual rise and fall of the nova will be.  The public will be mighty unimpressed when it goes off if it is only at 2nd magnitude a few hours.  They have been sold a big event, but this is going to be more of a blip naked eye from what I gather, even if it occurs at a convenient time in the evening and the skies are clear.   

 

At any rate, with all of the hype at least there should be some good data for evaluating what actually happens. 

[Xilman]

Nope, 16 and shrinking.   The AAVSO announcement he made was 2024.4±0.3 years.

Is that one-sigma error?

 

Serious question, because even 3-sigma event happen rather often, which is why the particle physicists insist on 5-sigma before anything can be counted as a discover.

[pvdv]

He has another paper with a more relaxed interval (and a more extensive analysis than in the "2024.4±0.3 years" paper.

https://arxiv.org/pdf/2303.04933

I wouldn't blame him too much to be honest. His approach, at least in the above paper, is reasonable. He also profusely thanks AAVSO, which means he's in very good terms with them, which in turn may have led AAVSO getting a bit over-enthusiastic about the other paper. The press got excited about it and it went viral. Nobody would care if he had written about something that had less "unwashed masses" appeal than a "new star".

Betelgeuse going Nova or not going Nova wasn't any better (much worse imho)

It will blow when it wants to, we'll learn new things when it does.

 

[Redbetter]

He has another paper with a more relaxed interval (and a more extensive analysis than in the "2024.4±0.3 years" paper.

https://arxiv.org/pdf/2303.04933

I wouldn't blame him too much to be honest. His approach, at least in the above paper, is reasonable. He also profusely thanks AAVSO, which means he's in very good terms with them, which in turn may have led AAVSO getting a bit over-enthusiastic about the other paper. The press got excited about it and it went viral. Nobody would care if he had written about something that had less "unwashed masses" appeal than a "new star".

Betelgeuse going Nova or not going Nova wasn't any better (much worse imho)

It will blow when it wants to, we'll learn new things when it does.

 

He had a bunch of predictions and was changing them frequently.  That paper was before the "dip", but made the assumptions that the dip was real and that it would be predictive.  In Schaefer's own words from the paper: 

"When the dip becomes first noticeable, we will get roughly 1 year advance warning and can make a prediction of the date accurate a month or two."  

 

He put all of his eggs into one basket.  And as has been pointed out the dip this time wasn't what he thought it was.

 

What is worse is that the sentence after that reads:  "In the band, the pre-eruption dip appears as a steady drop all the way to the day of the eruption. In the band, the last year of the pre-eruption dip

appears to have T CrB brightening steadily to the eruption from a minimum roughly one year in advance."

 

Clearly T CrB has done none of that this time around in either band.  Instead it has returned to its normal cycle.

 

It could go off any time and each day it is accreting toward a critical mass, so it will get there eventually.  But when it does it won't have anything to do with his recent dip prediction.

[yuzameh]

Nope, 16 and shrinking.   The AAVSO announcement he made was 2024.4±0.3 years.  He has until Sept. 12 UTC.    Sept. 13 and beyond is outside the window of the prediction.  If he wanted a wider range, he should have provided one.. 

I see, you got me!  For some reason I keep thinking it is mid August also, even though I'm aware of the date.  Dunno why, the swifts went back south a few weeks (there were far fewer this year, likely all the 'soffeting' that's in trend now, and their visits last about a month less adding both ends compared to the past) back so I should realise autumn approaches.

 

Alrighty, I'll get all pedantic and give him a few days leeway by saying 2024.4 can mean 2024.4000000000000000000000000r0 and 0.3 can be up to 0.3499999999999999999999999999999999999999999999999999999999999999999999999999999999r9 , that gives him 0.05 ish of a year extra which drags him _just_ into earliest Octember (ie mid Septober).

[yuzameh]

 

I wouldn't blame him too much to be honest. His approach, at least in the above paper, is reasonable. He also profusely thanks AAVSO, which means he's in very good terms with them, which in turn may have led AAVSO getting a bit over-enthusiastic about the other paper. The press got excited about it and it went viral. Nobody would care if he had written about something that had less "unwashed masses" appeal than a "new star".

Ah, well, you evidently aren't aware of his prior history in the cataclysmic variable and exploding star world of firm predictions based on vacuum evidence.

 

He's been at this prediction game a long time, sometimes in ways that it is hard to distinguish it from self-aggrandisement.  Granted he sometimes ends up being right, usually in collaboration though and with actual observers supporting with observations (although of course when the latter do not confirm there is rarely any paper, after all, sciency stuff rarely publishes negative results, albeit the occassional 'lower limit' determination).  He was involved in the fairly recent confirmation of the SN 1181 SNR being the same as Patchick 30 (part of said's candidate nova lists), but I'm not sure he was the team leader there.

 

I can't even remember half of them, I started dismissing them years ago, in the cataclysmic variable fora over the years his predictions or attempts to match CVs with 'historic' potential 'nova' from East Asian or other chronicles aren't new and I'm rarely tempted to read beyond the title of any of his papers nowadays.  He needs to use co-authors more, as a regulatory mechanism on his enthusiasm.

 

Suffice it to say exploding stars have timescales and can thus appear to be sort of predictable and if you play your prediction cards right and caveat yourself with this known unpredictability you can get it right sometimes even due to randonmness (as always being wrong would be non-random for stuff that is not pure artifice).

[yuzameh]

I am curious as to how short the actual rise and fall of the nova will be.  The public will be mighty unimpressed when it goes off if it is only at 2nd magnitude a few hours.  They have been sold a big event, but this is going to be more of a blip naked eye from what I gather, even if it occurs at a convenient time in the evening and the skies are clear.   

Have you got a copy of your Burnham's?  A graph of the 1866 and 1946 outbursts is included, both were very similar (however not sure how much of the 1866 one is extrapolated).  It goes boom in about a day or less, that's why when folk say it's mag 9 now after just starting an observing session they may well have seen it naked eye by the time they went to bed if they started observing early and finished late.

 

It stays at max about two days, and despite claims of mag 2 it may well be nearer 2.5 or 3.  It will plummet rapidly, not being naked eye more than a week, if that (I'm going from memory, I haven't dug out my Burnham's CH).  They'll be a negligible decrease in fade rate as it approaches minimum then that will level off before after a month or so it'll have a secondary outburst up to around mag 8 which will be broader and more symmetrical and rise and fall not quite as steep.  I really ought to look up any spectroscopy from the 1946 event and see whether that's shockwave or nuclear isotope decay*.  That's about a month or so, then flattens off.  Not sure when the ellipsoidal variation returns.

 

https://en.wikipedia...BLightCurve.png

 

(ignore the pre- rubbish, just look at the outburst and after, there is a 'dip' but it ain't in the lightcurve).

 

When it's nearest analogue, RS Oph recently outburst there was a lag of at least two days before swift could get to look at it, and longer for other multiwavelengths, so the hype may have helped the professionals pull their finger out, but mostly they weren't all that interested really as I think it had been fully followed with modern kit about two outbursts ago (memory says average of every six years for that one, misses in the past due to solar conjunction)

 

*Apparently spectra were observed in 1866 too, including by he pioneering Huggins, probably observing and measuring visually (can be done), although he was a pioneer astrophotographer too.  A quick glance at the spectroscopy, which I ain't even remotely good at, probably suggests shock wave stuff, maybe hitting material from past events????  No idea really, but not unprecedented.  Look up the R Aqr outburst in Burnham's on such stuff, a former symbiotic nova, said latter are kind of on the same gradation of phenomena from symbiotic stars in general to giant star primary recurrent novae.

 

Finally, if you want some clues on what might happen, websearch on results from the 2006 and 2021 outbursts of RS Oph, I caught the latter with binoculars near maximum (which gets up to mag 4), probably my first catch, and a coupla days just after, it too fades rapidly.  Has it been three years already!!!