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[vsnet-obs 2289] Re: Polaris

Dear Dr. Poyner and VSNET members; 

     I will send information on the variations in Polaris.  I'm 
  sorry for my rate reply and the incompleteness of information 
  which you will find in the latter half of this post.  Although 
  somebody already have sent information, which may be more 
  complete than this post, by a private mail,  I have received 
  no reply via VSNET till now.  I hope this post has some useful 
  information for Dr. Poyner and other VSNET members, who are 
  interested in Polaris.  

Gary Poyner wrote: 
> Does anyone know the current thinking regarding the variations
> in Polaris?  I seem to remember reading not so long ago that 
> it's amplitude had been declining for something like 50 years,
> and that perhaps it had now ceased to be a Cepheid altogether!

1. The paper Dr. Poyner have read may be 

  "Goodby to Polaris the Cepheid" by J.D. Fernie K.W. Kamper, 
  and S. Seager, which appeared in ApJ vol. 416, No.2, 820-824 
  (1993).  

     The authors have pointed out that the pulsatinal amplitude 
  of Polaris seems to be declining exponentially, and Polaris 
  may be leaving from the Cepheid instability strip.  

     I have found other authors also reporting the similar 
  result, however, unfortunately, I have no chance to read it.  

2.  In more recent literature,  the other authors re-analyzed 
  the variations of Polaris and reported that *pulsating amplitude 
  of Polaris seems to be declining not so dramatically*.  They 
  concluded that Polaris is not at the red edge, but still in 
  the Cepheid strip.  

     I'm sure that I have read above result, however, I'm not 
  sure on name of the author and where I have found this result.  
  I have tried to search it in some references in indexes of 
  some of the main journals,  but I have no clue for it.  It 
  may be appeared in a proceedings of a conference.  This is 
  the incompleteness I have wrote at the top of this post.  

> A couple of students at Birmingham University are desperate
> for information on Polaris, so I would be grateful if someone 
> could help out.

     As you might know, the observational constraints on the 
  red edge of the Cepheid strip brings us a fruitful information 
  on the stellar interior.  I would like to suggest to the 
  observers who are interested in the variations of Polaris that 
  more observations are needed to clearify whether this interesting 
  small amplitude Cepheid, Polaris, is really leaving the Cepheid 
  strip or not.  

Best 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) %