[vsnet-chat 68] Re: SRc variables as supernova progenitors

[Toshihito Ishida <ishida@nhao.go.jp>]

Dear T.Kato-san and chatters; 

Taichi Kato wrote in the message received on Thu Feb 13 22:01:02 1997
> 
> Dear Ishida-san and chatters,
> 
> > If we can do it, surely Dr. Kato is right.  However, if the SRc 
> > stage is so short in stellar evolution,  there exist only about 300 
> > (for example)  SRc variables in our Galaxy, may be.   
> 
>     It's a surprise to know SRc variables in the Galaxy are so rare.
> May I have some more questions regarding this?

I actually didn't know it's rare or not when I wrote this sentences.  
But, after receiving Kato-san's mail, I tried to make a quick 
inspection on this point from the electronic GCVS4 data in Selected 
Astronomical Catalogs, volume 1 (CD-ROM distributed by ADC, NASA).  

From the nice work by grep command,  I have found the following 
number of entries with 'SR'.  

SRA (including SRA:) -----  846 
SRB (same as above)  -----  896 
SRC (same as above)  -----   55
SRD (same as above)  -----   78

'SR'                 ----- 3456

Above 'SR' are 'contaminated' by 
PSR                  -----    2
ACV with spectrum type like A1P(CR-SI-SR) ----- 67. 

Number of semi-regular variable stars will be 3456 - 67 - 2 = 3387.  
(May be, there exists another 'contamination'.  However, it 
will be not so large.  ) 

3387 - 845 - 896 - 55 - 78 = 1512.  These stars do not have subclass 
type.  

Inspecting above results,  SRc variables seems to be actually rare.  

> 1) Do all SRc variables have masses enough for producing SNe?
>    If not, what fraction it might be, or can we select suitable targets
>    using other easily known parameters (period of pulsation etc.) ? 

In general,  massive star will pulsate in shorter period if it has 
the same luminosity and the same effective temperature with it's 
less massive counter part.  However,  pulsation in red giant stars 
are so complicated that the cycle length we observe may be caused  
from only the physical state of the outer atmosphere, and not from 
that of the total mass of the star.   

It is suspected whether the redder pulsating stars in the same 
subclass are in the same evolutionary stage or not.  It seems 
to be difficult to say clearly which is which.  

> 2) Of all SNe II progenitors, what fractions of individal variable star
>    classes (SRc, S Dor, ..) would be expected?  This knowledge might
>    partly answer Monard's vsnet-chat 65.  If most SNe II explode from
>    non-variable progenitors, I might lose my 1000-yr bet.

Unfortunately, I don't know either.  S Dor stars are very rare, but 
almost all of them seem to become a SN, which is awaited so long by 
all the variable star fans.  SRc stars are not so rare as S Dor stars, 
however the fraction to become SNe will be less than that for S Dor 
stars.  

Anyway, I'm sure that your loss will be only 100-yr or so at most :). 
Either for mine.  

regards, 

-- 
%  Toshihito ISHIDA, Ph. D., Astrophysicist                               %
%  Nishi-Harima Astronomical Observatory, Sayo-cho, Hyogo 679-53, JAPAN   %
%  Tel:     +81-790-82-3886 ext. 142      Telefax: +81-790-82-3514        %
%  e-mail: ishida@nhao.go.jp (usual) HQA01560@niftyserve.or.jp (off time) %

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