Profile variations of the H, He I 5876 and DNaI lines for different
observing runs are presented in Figs. 1 (click here)-5 (click here). To illustrate
a character of the rapid variability on time scales from hours to days, the
spectra obtained in neighbouring nights are gathered in separate groups.
For comparison the profiles corresponding to the initial dates of each group
are given as dotted lines.
Figure 1: Line profiles of H observed in the spectrum of HD163296\
in 1992 at the LNA. For the sake of comparison, the profiles obtained on
20.03 and 17.04 are also superimposed as dotted lines on the profiles of
the respective next observing nights
Figure 2: The same as Fig. 1 (click here) but for 1993. The dotted line
shows the profile obtained on 01.05
Figure 3: The same as Fig. 1 (click here) but for 1995. The dotted line
shows the profile obtained on 13.04. The nightly mean profile for
20.06 is presented at the bottom
Figure 4: Residuals with respect to the nightly mean
H profile observed on 20.06.95
On the whole, the profile type of the H emission line was the same as
in the ESO spectra of 1991-1992 (Paper I). However,
as is clearly seen in Figs. 1 (click here)-3 (click here), the system of
blueshifted absorption components turns out to be more complicated.
In different observing nights it contains one component
(20-21.03.92 and 02.03.93), two components (all the remaining dates except
for 31.08.93) or three components (31.08.93). On the latter date
a redshifted absorption feature was observed at about
.
The width of H profile remains practically constant with positional
shift of the profile as a whole from
(17.04.92)
to
(15.04.95).
Residuals from the nightly mean spectrum observed on 20.06.95
(the only date when several spectra were obtained during a night)
are presented in Fig. 4 (click here). They demonstrate the same character of
rapid variability as in 1991-1992 (Paper I).
It looks like monotonous changes of intensity within the narrow intervals
of radial velocities without positional shifts
(so called "standing waves'' in the residuals).
The He I 5876 line profile exhibits a somewhat smaller width in comparison
with H (Fig. 5 (click here)) and a positional shift from
(April, 1995) to
(20.03.92).
The majority of line profiles are blueshifted and double-peaked, with the blue
emission peak being stronger and the central absorption being slightly
redshifted. Occasionally, it acquires a reverse PCyg-type
(16.04.95 and 20.06.95, (b)-profile), while the (a)-profile of 20.06.95
exhibits an intense additional emission peak near zero velocity.
Figure 5: The same as Fig. 1 (click here) but for the He I 5876 and DNaI\
lines. The profiles obtained on 13.04.95 and 20.06.95 a)
are also superimposed as dotted lines on the respective subsequent
observations. The radial velocity scales for He I 5876 , and the D2 and
D1 lines are given in at the bottom. Spectrum a) was taken
at UT
, b) at
The DNaI lines are anomalously wide compared to classical Herbig Ae/Be
stars (Fig. 5 (click here)):
from (20.06.95) to
(March, 1992).
As a rule, the DNaI line profiles are of the same type as H
,
but the set of absorption components is more diverse. Sometimes
narrow redshifted features can be met in the DNaI profile,
such as that seen at
in the profile of 16.04.95.
polarimetric observations of HD163296 in July 17-31, 1995
give evidence of the presence of at least two
variable
linear polarization components.
A detailed periodogram analysis of the Stokes parameters Q and U
has been carried out by means of the Laefler-Kinman (1965)
method implemented in a computer code by Pelt (1980). We have
found the nightly mean values of the U-parameter to be satisfactorily
approximated by a sinusoidal curve with a period
days,
superimposed on a linear trend with the same slope in all three bands
and the mean value increasing towards longer wavelengths (Fig. 6 (click here)).
Variations of the Q-parameter are of essentially lower amplitude.
The noticeable difference of the trend component for the Q-parameter
in the R passband can be caused by the distorting influence of
the variable lowly-polarized emission in the H
line.
After subtraction of the trend, the variations of the Q parameter
in the
-bands can be fitted by a sinusoidal curve with the
same period (7.5 days) and
phase shift relative to the
corresponding U-curves, while in the I-band the sinusoidal variations disappear.
Figure 6: Illustration of the cyclic variability
of the nightly mean Q, U polarization parameters of HD163296\
in July, 1995
Measurements of circular polarization performed within the same observing set
allowed to derive weighted mean values in excess of the noise level
in all passbands, displaying an increase towards longer wavelengths
(
in the V band,
in the R band, and
in
the I band). Variations of the nightly mean values are weekly correlated
with those of the linear polarization degree.
These results imply the presence of aligned particles
in the dusty envelope of this object.