[vsnet-chat 3981] Re: Nc's and other peculiar variables

[Taichi Kato <tkato>]

Re: Nc's and other peculiar variables

Sebastian Otero wrote:

>             In light of the appearance of V445 Puppis I'd like to know
> which are the (spectral?) features that make possible to differenciate
> between a very slow nova and other types of star.
> Specially: FU Ori, V4334 Sgr, RR Tel...
> Most of them have been originally called novae but then clssification was
> changed (or remains ambiguous)
> 
> In other words: What is the point that let us know that V445 Puppis is not a
> Fuor, not a final-He flash object or an extreme case of a symbiotic star?

    FUors and symbiotic stars (at least in their typical forms) are all
hydrogen-rich.  This is the striking difference from V445 Pup (Kanatsu
Object).  Furthermore, FUors are from pre-main sequence stars, which are
usually associated with far-IR dust emission (circumstellar and star forming
region), which could have been detected by IRAS.  Symbiotic stars usually
have red giants, whose signature could have been easily detected by the
2MASS survey, but the possibility is rather unlikely becuase of the
relatively blue color of the progenitor.

    The remaining possibility as a final-He flash object is still uncertain.
They are usually hydrogen-poor.  The only spectrum we can compare with
is Sakurai Object (V4334 Sgr), which showed numerous carbon-related
absorption lines, not emission lines.  The expansion velocity of Sakurai
Object was far smaller than Kanatsu Object.  These are the main differences.
Sakurai Object is surrounded by nebulosity (fossil PN), but Kanatsu Object
apparently lacks such one.  There may be other varieties of final-He flash
objects, but we simply don't have other examples.
Despite the lack of clear hydrogen signature, Kanatsu Object bears roughly
similar characterstics to classical novae, in terms of emission lines from
elements heavier than oxygen.

Regards,
Taichi Kato

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