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\IBVShead{4346}{21 May 1996}

\title {THE SPECTRUM OF FG SAGITTAE IN 1995}

\begintext

The temporal behaviour of the remarkable variable star FG~Sge has
received much attention in the recent years due  to its unusual activity
after its sudden fading in 1992 (Papou\v sek, 1992). We have
routinely obtained some spectra of FG Sge every year, trying to detect
possible changes in its spectrum.
All our spectra from 1992 and onwards were obtained with the echelle
spectrograph ``Lynx" of the 6 m telescope of the Special Astrophysical
Observatory (Panchuk et al., 1993). These spectra cover the spectral
region $\lambda \lambda 5000\div 7200$.

In the spectra obtained in 1992
just few weeks before the dimming started, we identified C$_2$ Swan
bands clearly indicating that FG~Sge has become a  carbon star 
(Kipper \& Kipper, 1993). Iijima \& Strafella (1993) have found C$_2$
bands in low resolution spectra taken much earlier, in 1981. In our
spectra obtained in 1994 the C$_2$ bands were still present and in 
NaI D doublet a P Cygni--type emission has appeared. This allowed us to
estimate some parameters of
the  expanding shell around FG~Sge (Kipper et al., 1995).
 The intensities of emission components of the doublet  changed
in 1994 on the time scale of weeks. There were no
low--excitation heavy--element lines in emission, which, however, were
visible in the spectra obtained near the deep minimum in 1992
by Smith et al. (1995).

In 1995 FG~Sge changed in brightness in a quite sporadic manner from
$V\sim 10.5$ to $V\sim 13.0$ according to the data by Hungarian Astronomical
Association--Variable Star Section.
During the spectral observations on 9/10 and 10/11 August
FG~Sge was very faint (HAA-VSS data: $V\approx 12.5\div 13.0$,
according to Variable Stars Observers' League of Japan:
$V\approx 13.3$) and therefore
erroneously the visual companion
  8$^{\prime\prime}$ apart from FG~Sge was actually observed.
This is probably the first high resolution spectrum of the companion
ever obtained. The spectrum turned out to correspond to a 
quite normal
giant with the 
spectral type 
around K0. For more detailed classification some blue classification
spectra should be obtained. Adopting CI$=+1.50$ (Herbig \& Boyarchuk, 1968)
one could estimate with this spectral type (K0III) the distance of
the companion 
(3.3~kpc) close or larger to that of FG~Sge.
 The radial velocity of the companion is  $-34$~km~s$^{-1}$
(that of FG~Sge itself is 38~km~s$^{-1}$). The emission lines of
[OI], [NII], and H$_{\alpha}$
originated in the planetary nebula He~1--5, surrounding FG~Sge, are
clearly visible in the  spectrum of the companion.

The spectrum of FG~Sge itself was obtained on 12/13 December when
the star was relatively bright ($V\approx 10.5$). From February 1996
a new very steep fading of FG Sge started again (Mattei, 1996). There are
no drastic changes in the absorption spectrum compared with the spectra
obtained in 1992 and 1994. The C$_2$ Swan bands are still present and the
C/O abundance ratio is around 3.2. This value corresponds to the case
when  the solar O abundance and the effective temperature of 5500~K are
assumed for modelling and spectrum synthesis. Like  a year before the only
emission lines are the P Cygni--type emission components of NaI D lines.


\vfill \eject

\centerline{2}
\vskip 1mm
\epsfysize=12.5cm
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\normalsize
\begin{center}
Figure 1. The NaI D lines in the spectrum of FG~Sge obtained
on 12/13 Dec. 1995. The positions of zero-velocity photospheric lines
are indicated by asterisks. Some of the lines from the earlier
line--lists (Kipper \& Kipper, 1993; Wallerstein, 1990)
 are indicated with their identifications
or noted as unidentified (u.i.). The relative radial velocities of
components are indicated with arrows
\end{center}
\large
\vskip 5mm


As in 1994 the most drastic changes appeared in the profiles
of NaI D doublet shown in Figure 1. The wavelength scale in this Figure
takes into account the mean radial velocity $V_{\rm rad}=38$~km~s$^{-1}$
found for the spectral region $\lambda \lambda 5800\div 5920$.
The continuum level was estimated for the same region. We expect
the error in $V_{\rm rad}$ to be less than 3~km~s$^{-1}$. The sharp
components at nearly $-41$~km~s$^{-1}$ were also observed in
1981, 1992, and 1994 and correspond most probably to the interstellar
gas. In the spectrum of the companion these lines are not fully
resolved, causing only some extra absorption in the red wings of the
doublet. These components have the $V_{\rm rad}$ relative to the Sun
 about $-3$~km~s$^{-1}$. According to Langer et al. (1974) there is 
an interstellar cloud in the line of sight with $V_{\rm rad}=-6$~km~s$^{-1}$.
Taking into account the possible errors in radial velocities
it is obvious that the IS lines correspond to that cloud.

The absorption components at $-10$~km~s$^{-1}$ could correspond to 
expanding higher levels of the photosphere, but the apparent blueward
shift could well be the result of the blending with the emission
part of the profile.

\vfill \eject

\centerline{3}
\vskip 1mm

The circumstellar absorption components at --135 and --173~km~s$^{-1}$
 correspond to the shells ejected at different times. The complicated
structure of the doublet does not allow the quantitative analysis we
performed for 1994 spectrum.
\vskip 1cm

\beginauthors
T.~KIPPER
Tartu Observatory,
T\~oravere EE2444,
Estonia
\vskip 3mm
\authorsrightcol
V.G.~KLOCHKOVA,
Special Astrophysical
Observatory RAS,
Nizhnij Arkhyz 357147,
Russia
\endauthors

\references

Herbig, G., Boyarchuk, A., 1968, {\it ApJ}, {\bf 153}, 397

Iijima, T., Strafella, F., 1993, {\it IBVS}, No.\,3959 

Kipper, T., Kipper, M., 1993, {\it A\&A}, {\bf 276}, 389 

Kipper, T., Kipper, M., Klochkova, V.G., 1995, {\it A\&A}, {\bf 297}, L33 

Langer, G., Kraft, R.P., Anderson, K.S., 1974, {\it ApJ}, {\bf 189}, 509

Mattei, J.A., 1996, {\it AAVSO News Flash}, {\bf 18}

Panchuk, V.E., Klochkova, V.G., Galasutdinov, G.A., Ryadchenko, V.P.,
Chentsov, E.L., 1993, {\it AZh Lett.}, {\bf 19}, 1061

Papou\v sek, J., 1992, {\it IAU Circ.}, No.\,5604

Smith, V.V., Gonzalez, G., Lambert, D.L., Rao, N.K., 1995, Poster at
2nd Intern. Coll. on ``Hydrogen--deficient Stars"

Wallerstein, G., 1990, {\it ApJS}, {\bf 74}, 755

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