Betelgeuse spectrum please?

[PhotoGav]

Does anyone have a ‘pre-dimming’ spectrum of Betelgeuse I could borrow, please? Ideally using a SA100 grating, but not essential. I have just captured a spectrum this evening and would love a comparison spectrum. I guess ideally the raw capture that I can then run through BASS, but a processed spectrum would be perfectly acceptable!

Thanks. 

[Sunshine]

That comparison would be interesting to see, i hope someone has that for you.

[andrew s]

There are some on the BAA website under the discussion topic "Betelgeuse "

Regards Andrew 

[Carl Reade]

Love to see some spectrum guys results here. It does look dim to the naked eye. Are we in for a big bang?

[Sunshine]

4 hours ago, Carl Reade said:

Love to see some spectrum guys results here. It does look dim to the naked eye. Are we in for a big bang?

Maybe, I know one thing for sure, it could have already happened, just like it could in a hundred thousand years.

[PhotoGav]

9 hours ago, Carl Reade said:

Love to see some spectrum guys results here. It does look dim to the naked eye. Are we in for a big bang?

Probably not any time very soon, it’s just a variable star varying, but then again, maybe!?! I’m working on it (in my own back garden way!)... results to follow...

[andrew s]

We might get some early warning (assuming we are still a round) when it starts burning silicon into iron.

"Betelgeuse is so close that neutrino detectors might pick up the silicon burning phase, giving us more warning time than the usual neutrino warning system based on supernova neutrinos."

Source https://www.physicsforums.com/threads/betelgeuse-unusual-dimming-ready-to-supernova.982440/

I think the consensus is it is still well into the future on human time scales.

Regards Andrew

[PhotoGav]

Andrew, that's a very interesting link - thanks for sharing. All the evidence certainly points to the supernova theory being media hype. The interesting thing is to try and understand what makes Betelgeuse vary in the way that we see. One interesting entry in the discussion is the idea of a binary partner that has been engulfed by 'Betelgeuse A' and now orbits within the outer envelope of the A star, causing dimming every 5.x years as it transits the A star. Mmm, interesting idea!

[Davey-T]

Article in this months (February) AN with a few facts and figures.

Dave

[robin_astro]

Betelgeuse is one of the MILES standard stars  which was recorded in 2000/2001 when the brightness was more typical so you could compare with that (the non deredened version eg in ISIS, filtered to match the Star Analyser resolution.)  My spectrum with the ALPY 600 on 30th December 2019 shows only  very subtle changes in the visible spectrum compared to then

http://www.spectro-aras.com/forum/viewtopic.php?f=38&t=2433#p13514

and there has been  no further change up to 9th January. (The later spectrum is with the modified ALPY  at R~130 so the typical Star Analyser resolution)

http://www.spectro-aras.com/forum/viewtopic.php?f=38&t=2433&start=20#p13584

The spectra are in the BAA database

Cheers

Robin

Edited January 16, 2020 by robin_astro
typo

[robin_astro]

Note also that is possible that Betelgeuse may not actually be dimming at all when all wavelengths are considered as most of the radiation is in the IR  and a recent measurements in H,J bands in the AAVSO database appear to show no significant change.

 

[PhotoGav]

That's a fascinating observation, Robin. I will be using that! So, essentially it is just in certain wavelengths (the visible ones) that dimming has occurred.

[Victor Boesen]

I assume that means the star's temperature is slowly falling?? Since the emitted energy has shifted towards the infrared spectrum instead of the blue??

[PhotoGav]

Apparently its temperature has fallen by about 150 K.

[robin_astro]

1 hour ago, PhotoGav said:

That's a fascinating observation, Robin. I will be using that! So, essentially it is just in certain wavelengths (the visible ones) that dimming has occurred.

That is what the AAVSO data is suggesting. One caveat though is that the last two points were taken by the same observer who's name does not appear in earlier data so I would be interested in any corroborating evidence. There is some suggestion from I band spectrophotometry done using a Star Analyser that the drop in brightness reduces into the IR

https://www.cloudynights.com/topic/645652-betelgeuse-is-faint-for-it/?p=9904083

(part of a long thread with lots of other discussions and speculation on the subject)

  H,J band brightnesses are not  easy measurements to make and amateurs with the capability of measuring in the IR are rare (they use photelectric photometry, essentially a single pixel camera with an IR sensitive photodiode) 

https://www.aavso.org/infrared-photoelectric-photometry-program

AFAIK there was only one commercial instrument for work in the IR and that appears to have been discontinued

https://www.optecinc.com/astronomy/catalog/ssp/ssp4.htm

[robin_astro]

12 minutes ago, robin_astro said:

That is what the AAVSO data is suggesting. One caveat though is that the last two points were taken by the same observer who's name does not appear in earlier data so I would be interested in any corroborating evidence.

The long term trends for V,H and J do indicate though that The H,J IR bands have similarly been unaffected by previous dimmings suggesting we may well just be seeing a similar pulsation driven dimming though deeper than normal.