COMMUNICATIONS / MITTEILUNGEN
Distribution of Stars of Spectral Types F7 and Earlier in a Lyra Region
No. 68
Budapest, 1975
Abstract
A study has been made of the spatial distribution of early type stars
in a region of intermediate galactic latitude. Objective prism plates
were used to survey an area of 19.5 sq. degree in Lyra for all stars of
spectral type F7 and earlier down to 13th photographic magnitude.
524 stars were detected, for which spectral types and photographic
UBV colours were obtained. The stars were separated into four groups
-- spectral class A1 and earlier, A2-A7, A8-F2, and F3-F7 -- and the
space densities determined for each group. The space density
curves show that the first two groups both appear to be composed
of two kinematically distant subsystems, each having a Gaussian
velocity distribution but with a ratio of the velocity dispersions
of 1.8:1. These two subsystems probably differ in age and it may be
significant that the derived age difference, about 3 x108 years,
is close to the time-difference between two consecutive periods of
star formation predicted by the density wave theory of spiral structure.
Further observations, however, are needed to rule out other birth
mechanisms having the same characteristic time.
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