[vsnet-chat 100] 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 Tue Feb 18 11:01:03 1997
> 
> Toshihito Ishida wrote:
> > However,  as same as missed SRc stars, it is also possible that some 
> > other types of variables are miss-classified as SRc stars.  I wonder 
> > if miss-classification may not result to increase the number of SRc 
> > stars, rather may result to decrease it.  
> 
>    I have extracted from GCVS 4 to confirm Ishida-san's suspicion.
> 
> (omitted)
> 
>    Of all stars classified as SRC (or SRC:), 10 have no spectroscopic
> information of the luminosity class.  The number would be smaller enough
> than that of potential SRc stars presently only classified as SR (of course
> depending on the definition of the SRc class -- as Ishida-san pointed out).

I understand the situation.  Thank you for your kind explanation.  

And another comment.  
>    What about SRc stars in the LMC, as may have been inferred from the
> recent MACHO surveys?

I have seen a light curve for a low amplitude long period variable in one 
of the report of MACHO survey.  However, I have not seen one for semi-regular 
variables.  I think there are two reasons for the lack of SR variables in 
MACHO survey.  The first reason is the long period of SR variables.  
Moreover, we will need more observing time than regular variables for 
irregular ones until we find its cycle.  The second one is that the MACHO 
survey is not designed to observe variable stars but to find out microlensing 
events.   I once asked to one of the member of the MACHO collaboration,  
"Why we have not shown any data for classical Cepheids with longer periods?" 
He answered me  "There is actually no data because they are so bright that 
its images for MACHO survey are saturated." (!)  

I'm not estimating yet,  but SRc stars in LMC too saturated and there 
is no data at all in MACHO survey, may be.  If it's really the situation 
of MACHO survey,  we will need another massive survey for studying 
variable stars for precise estimation of the number of SN candidates.  

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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