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Robin Leadbeater's picture
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Grey ?

I Iooked at this but their claim that the extinction is grey is not the case here if one looks at the photometry in the IR where there was no reduction in H J bands and a smaller drop in R compared with B,V  which is also seen in spectra. Perhaps this can be explained by the large grained dust model but I am surprised they have not considered the available photometry data

andrew.j.smith1905's picture
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Yes somewhat strange

Strange indeed Robin, and suprising as the are both experts on red supergiants. Indeed EML has written a book on the astrophysics of Red Giants!

Maybe the IR bands are more sensitive to Teff than in the V . I will look at her book and see if I can find any comment on it.It will be interesting to see how the discussion develops.

Regards Andrew 

Robin Leadbeater's picture
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beyond 6700A

I see their spectra stop at 6700A before the larger changes in the spectrum become obvious

andrew.j.smith1905's picture
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Nice discription

In any event I found their discription of how the did the Spectrophotometry interesting.

Regards Andrew 

andrew.j.smith1905's picture
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New paper on the dimming.

A different take on the dimming: https://arxiv.org/abs/2006.09409

"Betelgeuse is the nearest Red Supergiant star and it underwent an unusually deep minimum at optical wavelengths during its most recent pulsation cycle. We present submillimetre observations taken by the James Clerk Maxwell Telescope and Atacama Pathfinder Experiment over a time span of 13 years including the optical dimming. We find that Betelgeuse has also dimmed by \sim20\% at these longer wavelengths during this optical minimum. Using radiative-transfer models, we show that this is likely due to changes in the photosphere (luminosity) of the star as opposed to the surrounding dust as was previously suggested in the literature."

Regards Andrew

Roy Hughes's picture
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Puzzled by \sim20\% in the

Puzzled by \sim20\% in the quote I looked at the .pdf and it's ~20%

got it now.

Xilman's picture
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Mark-up

\sim is the LaTeX markup for the ~character. Likewise \% for %, because % has a mark-up meaning in LaTeX.

Jeremy's picture
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Betelgeuse observing season

The current VSS Circular contains an article by Drs Chris Lloyd and Mark Kidger which reports that recent observations of Betelgeuse, after its summer conjunction, reveal that the star started to fade almost immediately after recovering from its historic fade last season.

An Astronomers Telegram a few days ago by Costantino Sigismondi and his team suggests that “a second dust cloud ejected by the star is passing over its photosphere along our line of sight”.

As Betelgeuse is now becoming visible, further observations are encouraged.

Don’t forget that you can also catch up on Mark Kidger’s excellent webinar on Betelgeuse on the BAA YouTube channel.

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There is an article on “A

There is an article on “A Year of Betelgeuse“ in the October edition of The AGB Newsletter:

https://www.astro.keele.ac.uk/AGBnews/issues/AGB279.pdf

Emily Levesque (U of Washington) discusses what the recent dusty dimming might mean for other red supergiants, On page 3 to 4

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