Download Be and Shell Stars by Miroslav Plavec (auth.), Arne Slettebak (eds.) PDF

By Miroslav Plavec (auth.), Arne Slettebak (eds.)

The foreign Astronomical Union Symposium No. 70 on Be and Shell Stars, the Merrill-McLaughlin Memorial Symposium, used to be held in Bass River (Cap Cod), Massachusetts, U. S. A. , from September fifteenth via 18th, 1975. Fifty-three astronomers from Argentina, Belgium, Canada, Czechoslovakia, France, Israel, the uk, the USA, and the Vatican attended and took part within the Symposium. This quantity, which parallels the particular application heavily, comprises the papers offered on the Symposium plus lots of the dialogue following the papers. New observational concepts and clean theoretical rules have resulted during the last few years in a renewed curiosity in Be and shell stars. At IAU Symposium No. fifty one on prolonged Atmospheres and Circumstellar topic in Spectroscopic Binary Sys­ tems, the Otto Struve Memorial Symposium, in Parksville, British Columbia, Canada, 3 years in the past, a few contributors expressed the desire to arrange a symposium on Be and shell stars. If we want to establish an legitimate 'Father of IAU Symposium No. 70', it might be Mirek Plavec who, in his skill as President of IAU fee forty two (Photometric Double Stars) asked and got the cooperation of Commissions 29 (Stellar Spectra) and 36 (Stellar Atmospheres), prompt an Organizing Committee, and wrote to the IAU normal Secretary in 1973 asking for that the IAU govt Committee approve the proposed confer­ ence as an IAU Symposium.

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These may represent dynamic phenomena in a moving envelope: dispersal of density inhomogeneities, or rotation of the envelope. 7 days) has been attributed to the rotation of the envelope with variable, inhomogeneous emission intensity (Hutchings, 1970). 6. Photometry The photometry of Be stars has been even more patchy and sporadic than spectroscopy. Here again, it has been found that variability exists on time scales from minutes to years and it is difficult to know (a) the true or undisturbed state of the star and (b) whether variations are in any way periodic.

Telescope was built especially for this work. It was a short Cassegrain instrument with a final beam of focal ratio of 15. The photometer used a 2' aperture, a filter slide thermos tatted to about ± 1°C, a cooled EMI photomultiplier with an S-20 cathode, photon counting electronics and print out. Emphasis was laid on ease of operation for one observer for long periods in complete darkness. 5 A halfwidth at half height; (b) a similar filter 60 A wide, always used in conjunction with a 10% transmitting neutral density filter.

Hutchings: We measured the broad underlying absorption in the Balmer lines from about H8 to H12 or so, using our wide scan oscilloscope machine. In these lines the emission is present only weakly in the center and on good (usually IIla-J) plates we could get good agreement between individual lines velocities. Henize: If I may comment on distribution with spectral type, the data from my southern Ha survey (now in press) may be of interest. It was something of a surprise to find that peak frequency among 1232 stars with spectral types (nearly all are HD types) occurred at spectral type B8 (207 stars) in contrast to the classical data by Merrill which showed an apparent peak at B3 (my data show only 110 stars of this type).

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