[vsnet-j 1449] VZ Cet

[Seiichiro Kiyota <skiyota@nias.affrc.go.jp>]

こんにちは。

S&Tに紹介があったのですが、ミラの伴星のVZ Cetのスペクトルを撮って、こう着円盤を持った白色わい星だろうということになった
ようです。

Title: The Mystery Companion of Mira Uncovered 
Authors: Bochanski, J. J.; Sion, E. M. 
Journal: American Astronomical Society Meeting 198, #12.08 

Abstract
The true nature of Mira's companion star "Mira B" has intrigued and troubled investigators for the past 30 years. In 
the FUV spectral region, which is free of contamination from Mira A, the nature of the line spectrum and continuum 
energy distribution provide important clues. We have analyzed numerous IUE archival spectra of Mira B, in the 
wavelength range shorter than 2600 ?, with high gravity photosphere and accretion disk models with vertical structure. 
An optically thick accretion disk model at high inclination with an accretion rate of 10-10.5 Mo yr-1 reveals large 
disagreement with the observed continuum. Higher accretion rates, as proposed by Reimers and Cassatella (1985), are 
even worse. We find that the Lyman α region and FUV continuum out to 2600 ? is best fit by a white dwarf with a 
surface temperature of 9000 K. Using the new Hipparcos distance to Mira AB (128 pc), our estimate of the observed FUV 
luminosity agrees with the bolometric luminosity of a 9000 K white dwarf. If this temperature is maintained by 
accretion, then the required accretion rate is only 5.45 x 10-12 Mo yr-1. If accretion is not a factor in the white 
dwarf temperature, then the cooling age of the white dwarf is 854 Myr, with a mass of 0.6 Mo. The details of our model 
fitting are presented together with a discussion of the implications for wind accretion efficiency and disk formation 
at large binary separations. 


　　　　　　　　　　　　　　　　　　　　　　　　既出の話題だったらごめんね　ＭＥＩ／ＮＥＫＯ



----
 Seiichiro Kiyota  skiyota@nias.affrc.go.jp
 Laboratory of Stress Physiology
 National Insititute of Agrobiological Science
 Tel:81-298-38-8384
 Fax:81-298-38-8347

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