Talk:Carbon star

message: Not much seems to happen, so I'll deal with it then. Cleanup plan:
topic name     	why doubt??                                                                                                                                                                          	status
red giant stuff	carbon stars are red giants, really?? The red giant article says red giants are K to M type, carbon stars are analogous to late G to M type, but never have G, K or M spectral types.	rewritten to be like red giants
CO stuff       	MrX (below) and me doubting CO to be maincharacteristix, i believe C2 and CN spectral band presence                                                                                  	some small reformulation
Duplicity stuff	MrX doubting most carbon stars being doubles                                                                                                                                         	rewritten
Visibity stuff 	MrX and me questioning hard-to-observe statement                                                                                                                                     	rewritten
Ablation stuff 	MrX and me questioning ablation and invisibility of carbon stars                                                                                                                     	missing – BSVulturis rewrote!
C spectra      	C:s are C-N, C-R, C-H, C-Hd, C-J, and a few CS:es.                                                                                                                                   	written
A provisional text is emerging in http://en.wikipedia.org/wiki/User:Rursus/Kol#Carbon_Stars. When better than the text in the article, it will replace the current article. Rursus 12:58, 6 January 2007 (UTC)
replies: text: Na, it won't – it would be much harder to read... I've changed my mind, I'll cut-n-paste extras from my article to the current. Rursus 15:03, 8 January 2007 (UTC)
thread_title: Carbon star cleanup plan

message: Must fix Carbon Star#The Revised Morgan-Keenan system table - it's not consistent with the rest of the text. I made the table, I'll do it if none else happen to be faster: then be welcome! Rursus 13:15, 20 January 2007 (UTC)
thread_title: Must-fix

message: I am skeptical about some of the information in this article.
:Hi, Mr X!! How's Ms Y doing? I'll comment some on this, because I initially wanted to sketch some future improvements of this page. Rursus 12:42, 23 October 2006 (UTC)
replies: text: I remember the ordinarily distinguishing features as C2-, CN- and CH- absorption in the blue, so: agreed!. Besides, carbon stars aren't what we precisely call red giants, since red giants IMHO are M type stars, but there's ambiguities of meaning there. Rursus 12:42, 23 October 2006 (UTC)
replies: text: I object against Red Giant = M Giant. I'm not sure of any spectral characteristic – rather they are late-type (G to M) and has some C2-, CN- and CH- bands. Rursus 15:18, 4 January 2007 (UTC)
replies: text: No, TiO Rursus 15:20, 4 January 2007 (UTC)

text: The original author got it very wrong - carbon stars are red which makes their magnitude very hard to estimate by the eye, due to the Purkinje effect. Other means of observation recommended. Rursus 12:42, 23 October 2006 (UTC)

text: Agree. Rursus 12:42, 23 October 2006 (UTC)
thread_title: Skeptix

message: I've overhauled the description of the binary carbon star scenario to make it clear that the carbon came from the star that is now the white dwarf -- but it came when that star was not a white dwarf.  Included is a reference and link to Bob McClure's paper describing these carbon stars and other related objects.  I think this should alleviate the "disputed" nature of the material, though I've left the tag in there for now.
The R CrB stars (there's a number of them) mentioned above on this page are a wierd bunch of beasties, being hydrogen-deficient as well as carbon-rich; they seem to be single.  I left them unmentioned in the main article.  If anything, they deserve a stub article on their own.  They are carbon stars in the sense that there's more carbon than oxygen in the atmosphere, but they are almost certainly distinct from the other carbon stars, and are now referred to as "hydrogen-deficient carbon stars" in the discipline to make their difference clear.  Last I heard they were suggested to come from WC-type Wolf-Rayet stars, but that remains (as far as I know) unresolved and not fully accepted. 
I deleted the word "ablated" ... that's entirely the wrong concept for the shells around carbon stars.
BSVulturis 17:33, 13 December 2006 (UTC)
replies: text: This was far time ago, so now both the R CrB stars and the variable type RCB have their own articles. Said: Rursus (☻) 13:43, 26 October 2008 (UTC)
thread_title:  Binary scenario 

message: "Many of these extrinsic carbon stars are not luminous or cool enough to have made their own carbon, which was a puzzle until their binary nature was discovered."
I don't understand. Extrinsic carbon stars are not luminous enough or are too cool.... 
Doesn't the core carbon formation need high temperature or pressure?
128.195.84.188 00:20, 11 June 2007 (UTC)
replies: text: Correct: the "not luminous or cool enough" refers to the surface temperature.  The creation of the carbon takes triple-alpha process fusion, and then the subsequent deep convection to get that synthesized carbon to the surface layers requires a yet higher core temperature (and hence higher luminosity and cooler surface temperature).  Therein was the puzzle: extrinsic carbon stars are unlikely to be evolved enough, that is, to have ever reached the stage at which carbon synthesis and dredge-up happened in them.  The mass transfer idea gets around that problem. So, I need to find the time to whip the language into better shape.  BSVulturis 22:24, 3 August 2007 (UTC)
thread_title:  High Temp. needed to make carbon (more luminous, perhaps, or hi pressure) 

message: This page needs updates in mentioning the CEMP types.  Carbon-Enhanced Metal-Poor star.
* CEMP
** CEMP-α
** CEMP-r
** CEMP-r-II
** CEMP-s
** CEMP-r/s
** CEMP-no
** CEMP-no/s
* NEMP, Nitrogen-Enhanced Metal-Poor star (theoretical)
Thanks, Marasama (talk) 18:13, 3 June 2009 (UTC)
replies: text: CEMP star. I'll make some investigation whether they are carbon stars really. Rursus dixit. (mbork3!) 19:10, 18 April 2017 (UTC)

text: CEMP stars and Carbon stars are two different things. No harm in mentioning this in the article though, to reduce the possibility of confusion. Lithopsian (talk) 19:20, 18 April 2017 (UTC)
replies: text: It seems so, but one must distinguish between observational types and physical kinds. Carbon stars is the older observational type defined by Swan bands and heavy lines of carbons, it not a coherent physical kind. CEMP is the newer observational type, it is defined by low metallicity (diverse MP:s) with primarily CH added. CEMP were discovered in a specific search for the oldest stars, while carbon stars were just discovered without expectations, when the classifying of star spectra was in its infancy. Whether there is an observational criteria overlap or not, I don't know yet. It seems CEMP-no is a natural kind, but I don't know yet, regarding the other CEMP:s. Rursus dixit. (mbork3!) 07:36, 19 April 2017 (UTC)
replies: text: It appears that there is some connection between CH stars and CEMP stars, there might be a common underlying mechanism ("physical kind") shared by CH stars and some kinds of CEMP stars. And CEMP-no might not be a physical kind. Rursus dixit. (mbork3!) 15:02, 20 April 2017 (UTC)
thread_title:  CEMP is missing 

message: "Other elements formed through helium fusion and the s-process are also "dredged up" in this way, including lithium and barium." Barium can't be right; it's far too big an atom. Should that be beryllium or boron? RTBoyce (talk) 12:01, 8 October 2016 (UTC)
replies: text: Beryllium (specifically . Its half-life is only 59 days, but it's still listed in the significant products of hydrogen burning - Astrophysical Formulae, table 42 (page 422 in the 2nd edition). Tarl N. (discuss) 23:20, 8 October 2016 (UTC)

text: The article mentions both the products of helium fusion and of s-process neutron capture.  Barium is one of the most common s-process elements found in AGB atmospheres after a third dredge-up. Lithopsian (talk) 12:58, 9 October 2016 (UTC)
replies: text: Thanks - If I'd spent more than the 60 seconds I did thinking about it, I would have realized that a 59-day half-life is way insufficient for nuclei to make it from the core to the surface. Do you have a cite we can use on this, so some other enthusiastic amateur doesn't make the same mistake? Barium (All the way down at element 56) is certainly not what I'd guess would be a common element associated with Lithium in being dredged up from the S-process. Tarl N. (discuss) 01:00, 12 October 2016 (UTC)

text: Of course Ba can be dredged up. It is not a diffusion process, it is a convective movement that mixes the envelope with the core. Even though Ba ions (neutral atoms aren't likely) are heavy, they might be "swept up in the wind". Rursus dixit. (mbork3!) 10:07, 20 April 2017 (UTC)
thread_title:  Barium? 

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thread_title:  External links modified 

message: Is an Extreme Carbon Star something that is distinct?  Is it too specific?  Should there be a redirect from Extreme Carbon Star to this article?  RJFJR (talk) 01:48, 18 January 2019 (UTC)
replies: text: As best I can tell from the articles which refer to extreme carbon stars, they are referring to appearance (particularly sooty), rather than necessarily any extreme composition. Tarl N. (discuss) 07:02, 18 January 2019 (UTC)

text: Extreme carbon stars are not really distinct objects.  Extreme is an adjective to indicate that such stars are carbon stars with particularly strong characteristics of the class: high C/O ratio; low temperature; highly self-obscured to the point of optical invisibility.  There could be a redirect to here, or the extreme can be ignored and the carbon star bit linked as is.  A section in carbon star might be nice, maybe a separate article one day if someone really went to town on the subject.  Lithopsian (talk) 14:48, 18 January 2019 (UTC)
thread_title:  Extreme Carbon Star?