Betelgeuse Fainting

[chornedsnorkack]

The visible light is a small fraction of infrared. During a fainting leg, what stays closer to constant: the power of infrared separately, or visible and infrared combined?

[trinitree88]

The visible light is a small fraction of infrared. During a fainting leg, what stays closer to constant: the power of infrared separately, or visible and infrared combined?

chornedsnorkack. I think it's the total of the two together, known as the total bolometric magnitude. Bolometers are sensitive calorimeters with a wide spectral range. pete

SEE:https://en.wikipedia.org/wiki/Bolometer


A similar thing happens in R Cor Bor stars, where they periodically puff out carbon soot clouds. Should an R Cor Bor star have sufficient mass to go supernova, the late time evolution of the iron group isotopes delineated by Patton ,Lunardini, Farmer, and Timmes...about 5 hours before the prompt neutrino burst, ought to signal an imminent supernova by its distinct infrared brightening of the dust cloud with coherent neutrino/ nucleus interactions increasing by roughly a factor of 100 over previous days. Dust emission being fairly approximately blackbody....the temperature is ~ the fourth root of the (infrared luminosity)/(Stefan -Boltzmann constant)....(AAPT..pete's talk at Williams College, 1993..."R Corona Borealis, Infrared Enigma." you don't often get a ready-made neutrino luminosity detector as an astronomer or physicist.

R COR BOR stars...variable SEE:https://en.wikipedia.org/wiki/R_Coro...ealis_variable

Patton, Lunardini, Farmer, Timmes SEE:https://arxiv.org/abs/1709.01877

[chornedsnorkack]

How much energy is spent to diminish Betelgeuse´s binding energy on the fainting/expansion leg, compared to the visible and total brightness?

[trinitree88]

How much energy is spent to diminish Betelgeuse´s binding energy on the fainting/expansion leg, compared to the visible and total brightness?

chornedsnorkack. Can't answer that. Someone who might could be in the following ArXiv link. SEE:https://arxiv.org/abs/2002.10463
They think the most likely cause is large dust grains, that extinguish a broad spectrum of Betelgeuse's optical output
Expelled dust has a tendency to "mature", with smaller grains disappearing, and larger ones increasing slowly to even larger sizes. It's a statistical mechanics kind of thing, like Ostwald ripening of photographic emulsions. The peripheral atoms on the small grains can sputter off, and then re-attach. But chances are, the free moving grains are more likely to land on the larger surface of a bigger grain, than the smaller surface of a little one. When it happens repeatedly, the larger grains grow, and the small ones completely sputter away.
In photography, the effect occurs in gelatin/silver halide emulsions with water being the agent, but in stellar atmospheres, its expelled gases, cooling to grains in space, and then sporadic exposure to outbursts of hotter material to initiate the sputtering.

OSTWALD ripening, SEE:https://en.wikipedia.org/wiki/Ostwald_ripening

[Roger E. Moore]

Might be of interest to those in this thread...

https://arxiv.org/abs/2002.10463

Betelgeuse Just Isn't That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse
Emily M. Levesque, Philip Massey
(Submitted on 24 Feb 2020)

We present optical spectrophotometry of the red supergiant Betelgeuse from 2020 February 15, during its recent unprecedented dimming episode. By comparing this spectrum to stellar atmosphere models for cool supergiants, as well as spectrophotometry of other Milky Way red supergiants, we conclude that Betelgeuse has a current effective temperature of 3600 +/- 25 K. While this is slightly cooler than previous measurements taken prior to Betelgeuse's recent lightcurve evolution, this drop in effective temperature is insufficient to explain Betelgeuse's recent optical dimming. We propose that episodic mass loss and an increase in the amount of large-grain circumstellar dust along our sightline to Betelgeuse is the most likely explanation for its recent photometric evolution.

[George]

Might be of interest to those in this thread...

https://arxiv.org/abs/2002.10463

Betelgeuse Just Isn't That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse
Emily M. Levesque, Philip Massey
(Submitted on 24 Feb 2020)

Given the likelihood of the large discharge of gas and dust, won't the scattering effects distort the spectral distribution results, which compares Big B to close analog temperatures?

[trinitree88]

Given the likelihood of the large discharge of gas and dust, won't the scattering effects distort the spectral distribution results, which compares Big B to close analog temperatures?

George. Yep. Mostly optical converted to infrared. The total bolo metric magnitude should be roughly the same, or it requires a lot of hot mass to cool too quickly. The article suggests less than 100 K of cooling.
R Corona Boreal is stars behave similarly, with a variety of mechanisms suggested. As I am not an astronomer, I try not to stick my head in the guillotine too much. It always impresses me how observers can tease new information out of old data, and ever more sensitive instrumentation..
pete

[George]

George. Yep. Mostly optical converted to infrared. The total bolo metric magnitude should be roughly the same, or it requires a lot of hot mass to cool too quickly. The article suggests less than 100 K of cooling.

Yes, thanks because that matches the report from here, though I had to jump to the summary to find that value. It seemed to me, perhaps due to problems in my speed reading, that they were implying only a 50K change by noting the prior 3650K Teff and it is current value of 3600K Teff.

R Corona Boreal is stars behave similarly, with a variety of mechanisms suggested. As I am not an astronomer, I try not to stick my head in the guillotine too much.

Wise man. I really hate it when that happens to me.

It always impresses me how observers can tease new information out of old data, and ever more sensitive instrumentation.

Yes and that's part of my reason for asking because sometimes my snorkeling with pros allows me to go to new depths below (or above).

So I assume the shift to IR will skew what might be a fair, or semi-fair, Planck distribution but in a way astronomers can model to determine effective temperatures.

[Superluminal]

Just made my nightly observation of Betelgeuse. Maybe local atmospheric conditions or perhaps I'm looking too hard, but it seems to be redder than average. Used 7X50 binoculars. Brighter than Bellatrix.

[CJSF]

I noticed the "enhanced" redness (to my eyes) the past couple of nights it was visible. It also definitely looks brighter to me (though the actual numbers may not support a visual discernment and it's just my brain "knowing" it is brighter changing my perspective).

CJSF

[chornedsnorkack]

So Betelgeuse is supposed to have stopped being black, by emitting too much far IR and not enough near IR compared to the normal Rayleigh tail of a black body.
At what wavelength specifically is the far infrared excess being observed?

[trinitree88]

So Betelgeuse is supposed to have stopped being black, by emitting too much far IR and not enough near IR compared to the normal Rayleigh tail of a black body.
At what wavelength specifically is the far infrared excess being observed?

chornedsnorkack That's a little tricky. I found no recent IR survey of Betelgeuse. There are papers for supernova dust that is now believed to form in the first two years after BOOM, as the refractory elements of silicon, magnesium, and iron have their spectral signature disappear in the expanding ejecta, whilst the IR excess begins to appear at 9.7 microns and 18 microns. The author, Dwek has decades of dust experience, and lucidly argues for a rapid formation of silicates, with the stretching of Si-O bonds and the bending of O-Si-O bonds doing the emission. For Betelgeuse, it's a little different since the presence of heavy metals in the atmosphere is far less evolved in an old red giant, and there'd be more carbon compounds present from the CNO cycle. Repetitive pulsations can drive complex gas phase chemistry with Betelgeuse, and examination of the extended atmosphere will show that. SEE: DWEK SEE:https://arxiv.org/pdf/1812.08234.pdf
The Patton, Lunardini, Farmer, Tifft paper indicates that Betelgeuse ought to give a JUNO neutrino signal of ~ 200 events with ~ 2 hours to go before core collapse. That's irrespective of COHERENT scattering off nuclei which by the Akimov paper (Kate Scholberg), is a million times larger in the same energy range (PLFT, page 12 first paragraph. POST 122 this thread) pete

That'd make ~ 200, 000,000 events in a JUNO detector from a star at ~ 700 lt-yrs.

[Roger E. Moore]

Article with linked paper on how Betelgeuse is expected to explode.

https://phys.org/news/2020-02-physic...pergiants.html

[StupendousMan]

So Betelgeuse is supposed to have stopped being black, by emitting too much far IR and not enough near IR compared to the normal Rayleigh tail of a black body.
At what wavelength specifically is the far infrared excess being observed?

Some recent near-infrared observations made with a ground-based telescope are described in Astronomer's Telegram 13518:

http://www.astronomerstelegram.org/?read=13518

[trinitree88]

Some recent near-infrared observations made with a ground-based telescope are described in Astronomer's Telegram 13518:

http://www.astronomerstelegram.org/?read=13518

Stupendousman. Ok, R.D.Gehrz et al conclude from the stable near - IR, that the total bolometric magnitude is unchanged. That would be consistent with a change in the dust extinction, which takes a while to mature from a new abundance of added fine dust, to a larger population of bigger grains....the approximately 420 days cyclical behavior of the light curve.
pete

[Hornblower]

I took a look at dusk as the brighter stars were becoming visible. Betelgeuse and Bellatrix looked equal within my observing uncertainty, as they have for the past few weeks. While not suitable for quantitative comparison with a stars over a range of brightness, the bright sky made small differences, if any, very apparent.

Today at dusk I started looking when only Sirius, Rigel and Procyon were visible. As the sky darkened I saw Betelgeuse first, followed by Bellatrix a couple of minutes later. I would say no major change in the past three weeks.

[CJSF]

According to Betelbot, it's gained something like .3 mag in the last week or so, and it looks brighter to me. The AAVSO data clearly show a nice brightening trend over that time as well.

CJSF

[antoniseb]

Today at dusk I started looking when only Sirius, Rigel and Procyon were visible. As the sky darkened I saw Betelgeuse first, followed by Bellatrix a couple of minutes later. I would say no major change in the past three weeks.

It is not back to its full brightness, but I saw it as clearly brighter than Bellatrix, which 3 weeks ago it looked either the same or slightly dimmer than. AAVSO graph gives more detail, but shows that more experienced observers came to the same conclusion a bit more precisely.

[publiusr]

Now it seems to be the North Star that is acting up
https://www.livescience.com/north-st...d-mystery.html

[Hornblower]

I just looked at Orion under fading twilight. To my eyes there is no question that Betelgeuse has brightened from its recent faintest level. It looked brighter than Bellatrix but still fainter than Aldebaran. I would put it about midway, with some uncertainty.

[dethfire]

Here is a comprehensive thread on the subject
https://www.physicsforums.com/thread...ats-up.982440/

[CJSF]

I just looked at Orion under fading twilight. To my eyes there is no question that Betelgeuse has brightened from its recent faintest level. It looked brighter than Bellatrix but still fainter than Aldebaran. I would put it about midway, with some uncertainty.

That's about my assessment as well.

The nearly parabolic shape of the dimming event can be seen well with the AAVSO data via @Betelbot on Twitter.

CJSF

[Roger E. Moore]

Amazing, nice computer animation of a red giant's surface super convection cells, like on Betelgeuse. Takes a moment to get running on full.

https://scitechdaily.com/is-betelgeu...snt-that-cool/

[trinitree88]

I am making an amendment to my post # 132 in this thread. The Patton et al paper suggests that the modern argon detector should see 200 events @ about 700 light years, as scintillating picked up by photodetectors. I had noted that'd make about 200,000,000 coherent neutrino/ nucleus scatterings, since the work of Akimov, Scholberg ( Nature,2017) indicated the coherent cross-sections were a million times larger.
Using inverse square law, 700 lt- years to Betelgeuse, vs about 165,000 lt- yrs to SN1987A in the Large Magellanic Cloud, that'd reduce the interactions by a factor of 0.000015. That would have been a little over 3,000 events in the Rome and Maryland gravity wave detectors for the core collapse, and from Patton's previous paper on beta processes, 1.0-10 % of that in the last 5 hours before collapse, indicating the " anomaly" seen by Guido Pizella about, 5 hours before SN1987a, was real.
arXiv:2003.05844v1 [astro-ph.SR] 12 Mar 2020 page 8.... top right paragraph

pete

Scholberg's talk at MIT's Physics Colloquium April 26, 2018, indicated that COHERENT scattering was detected at 6.7 sigma

[Superluminal]

Betelgeuse is still rising. I wonder how the speed compares to how fast it came out of past faintings?

[antoniseb]

Betelgeuse is still rising. I wonder how the speed compares to how fast it came out of past faintings?

You can look at the AAVSO website and see. The time it is taking to rise is roughly the same amount of time it took to rise from previous dips. This dip a little deeper, so the millimagnitudes per day is slightly higher.

[Superluminal]

First observation in several days. Seems almost as bright as Pollux, +1.1.

[Superluminal]

Now brighter than Pollux.

[Superluminal]

Now very nearly as bright as .09 mag. alderbaran.

[Roger E. Moore]

Now very nearly as bright as .09 mag. alderbaran.

Once Star Maker blows off the dust, it gets shiny again!