Talk:Beta Cephei variable
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Main sequence?[edit]
The article says these are main sequence stars, but the first handful I looked up included two giants, a subgiant, and a supergiant. Lithopsian (talk) 22:12, 25 January 2013 (UTC)
- Oh dear, now I'm talking to myself. Despite the spectral classifications, all these stars appear to be hydrogen-burning objects, hence on the main sequence. They do appear to be slightly evolved away from the ZAMS, both from observation and theory, but not yet to the point of core hydrogen exhaustion. Spectroscopic luminosity classes can be influenced by pulsations and are relatively insensitive for B stars. Lithopsian (talk) 20:55, 1 August 2015 (UTC)
- Coming across exceptions and caveats to the I-V rating system fairly often......Cas Liber (talk · contribs) 23:29, 1 August 2015 (UTC)
- Spectral luminosity classes don't always map cleanly to stellar evolutionary states. The clearcut division in low mass stars between main sequence luminosity class V and giant star luminosity class III doesn't really apply for hot stars. Red giants are fully established hydrogen shell burners or helium burners. Blue giants are not, they are an early transitional phase on the way to red supergiants. Main sequence B stars evolve slowly towards higher luminosity, and slightly cooler temperatures, as their core hydrogen fraction drops. As the hydrogen fraction drops very low, the whole star contracts. Fusion output does not change significantly as hydrogen fusion continues in the core, but the luminosity increases from gravitational energy, and the temperature increases significantly. In the late stage of core hydrogen fusion, the star may already show a sub-giant or giant spectral class, although there is very little difference in physical parameters from a main sequence spectral class, and they form a fairly narrow band just right of the main sequence. When core hydrogen drops to zero, hydrogen shell burning becomes established and the star starts to expand at roughly constant luminosity. It rapidly (Hertzsprung gap) moves to a red giant (low mass B star) or supergiant (higher mass B star). B giants may be hydrogen shell burners, but this is a very short phase and most of them are core hydrogen burners (a tiny number are weird stars like extreme horizontal branch, blue stragglers, etc.). Lithopsian (talk) 13:39, 2 August 2015 (UTC)
- Coming across exceptions and caveats to the I-V rating system fairly often......Cas Liber (talk · contribs) 23:29, 1 August 2015 (UTC)
- This shows the locations on the HR diagram nicely. The theoretical pulsation regions are a little out of date, but you get the idea. Lithopsian (talk) 19:31, 2 August 2015 (UTC)
The list[edit]
@Lithopsian:, @StringTheory11: - shall we move all the discounted ones to a separate list of "former/excluded/possible" BCEP stars at the bottom? I do like hte idea of keeping them somewhere on the page and thus illustrating that science can be dynamic and difficult....(bit like deleted scenes on a DVD :)) I think it looks a bit silly to have a list of BCEPs with several saying, "Oh BTW this isn't one".... Cas Liber (talk · contribs) 22:31, 10 August 2015 (UTC)
- I agree. StringTheory11 (t • c) 23:39, 10 August 2015 (UTC)
- Yes, better only to have Beta Cephei variables in a list of Beta Cephei variables. The only glitch might be the hybrids, but I think they should stay. Lithopsian (talk) 13:02, 11 August 2015 (UTC)
Jargon or undefined symbol[edit]
The first sentence in the body (after the index) ends with a symbol that looks like a circle with a dot in it. For the sake of all non-astronomers who may read this page on Wikipedia (there will be many, since this article was on Wikipedia's intro page August 14, 2015), please define terms and symbols like this one. Or at least hyperlink it to a page that will explain it. Thank you! 68.52.75.29 (talk) 01:57, 14 August 2015 (UTC)