Spatial Distribution and Kinematics of OB Stars
  The sample of 37 485 suspected OB stars selected by Gontcharov (2008) from
the Tycho-2 catalogue has been cleaned of the stars that are not of spectral
types OV--A0V. For this purpose, the apparent magnitude $V_T$ from Tycho-2, the
absolute magnitude $M_{V_T}$ calibrated as a function of the dereddened color
index $(B_T-V_T)_0$, the interstellar extinction $A_{V_T}$ calculated from the
3D analytical model by Gontcharov (2009) as a function of the Galactic
coordinates, and the photometric distance $r_{ph}$ calculated as a function of
$V_T$, $M_{V_T}$, and $A_{V_T}$ have been reconciled in an iterative process.
The 20 514 stars that passed the iterations have $(B_T-V_T)_0<0$ and
$M_{V_T}>-5$ and are considered as a sample of OV--A0V stars complete within
350 pc of the Sun. Based on the theoretical relation between the dereddened
color and age of the stars, the derived sample has been divided into three
subsamples: $(B_T-V_T)_0<-0.2^m$, $-0.2^m<(B_T-V_T)_0<-0.1^m$, and
$-0.1^m<(B_T-V_T)_0<0^m$, younger than 100, $100-200$, and $200-400$ Myr,
respectively. The spatial distribution of all 20 514 stars and the kinematics
analyzed for more than 1500 stars with radial velocities from the PCRV and RAVE
catalogues are different for the subsamples, showing smooth rotations, shears,
and deformations of the layer of gas producing stars with the formation of the
Gould Belt, the Great Tunnel, the Local Bubble, and other structures within the
last 200 Myr. The detected temporal variations of the velocity dispersions,
solar motion components, Ogorodnikov--Milne model parameters, and Oort
constants are significant, agree with the results of other authors, and show
that it is meaningless to calculate the kinematic parameters for samples of
stars with uncertain ages or with a wide range of ages.
