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\input ibvs2.sty

\begin{document}
\IBVShead{4565}{9 March 1998}

\IBVStitle{New Periods for Variable Stars in Cygnus}


\IBVSauth{R.~G\'ALIS, L. HRIC}

\IBVSinsto{Astronomical Institute of the Slovak Academy of Sciences, 059~60 Tatransk\'{a} Lomnica, The Slovak Republic e-mail: galis@ta3.sk, hric@ta3.sk}

\IBVStyp{ * }
\IBVSkey{photographic photometry}

\begintext

This work summarizes the results of photographic photometry obtained over
24 years at the Skalnat\'{e} Pleso (1979-1993) and Asiago (1969-1988)
observatories. The periods of light variation, the epochs of the maxima or
of the minima, the types of variability for 17 variable stars are presented.

A total of ninety photographic plates of 9x12 cm and 24x24 cm formats
with emulsions ORWO ZU-2 and ORWO ZU-21 was obtained using the 30/150 cm
astrograph of the Skalnat\'{e} Pleso Observatory.
The limiting magnitude of the observational material is about 16.5 $\rm m_{pg}$.
The resulting photographic magnitude is close to the photoelectric B one.
At the Asiago Observatory 85 photographic plates  were taken using
the Schmidt telescope (67/92/215 cm).
On the basis of this material Margoni and Stagni (1984) and Margoni
{\it et al.} (1989) found 99 new variable stars.
Thanks to Professor Margoni (1993), who has provided us with his original
material in the reduced form, we were able to extend our observational
material and to double the time interval investigated by us.
During the complex survey of the combined observational material, we have
identified and selected 17 variable stars for next investigation.
Stars from the close neighbourhood of V1329 Cygni whose magnitudes were
measured by L. Kohoutek were used as comparisons, as well as those used as
comparisons by Margoni, 18 objects in total.

On the basis of the measurements obtained by iris microphotometer
we have constructed the sensitometric characteristic for
each plate, with the help of which the photographic magnitudes of the
individual stars studied were determined. Moreover, the heliocentric
correction was applied to all the JD of the exposures.
Our main aim was to determine new periods or improve the accuracy of the
periods already known for all the variable stars studied. With this purpose in mind,
we have performed a period analysis of all the data, using the method
of Fourier analysis (Deeming 1975, Kurtz 1985), the phase dispersion
minimization method (Stellingwerf 1978) and the method
of Fourier harmonic analysis (Andronov 1995) which fits the first harmonic
term of trigonometric polynomial to the observed data. The advantage of the
last method is the fact that it provides one not only with the determination
of the parameters of variability alone, but also with the determination
of the corresponding errors. Further result of the analysis is determination
of the moments of maxima (eventually minima) of the light changes through
the routine by R. Kom\v{z}\'{\i}k (1995), making use of the following
methods: the parabola fit, the polynomial fit, the ``center of mass", Kwee
and Van Woerden, the sliding integrations and the tracing paper polygonal
line. The averages of values obtained through the individual methods were
considered as the resulting values. The moments of maxima and minima are
determined at about the mid-time of the observational interval. The
type of the variability was determined as the last parameter, on the basis
of the length of the period, the amplitude of light changes, the shape of
light curve and with the help of the characteristics defined in the GCVS.

All the results obtained through the analysis of seventeen variable stars
which have been objects of our study are well-arranged described in Table 1.

\begin{table*}[tbhp]
\small
\begin{center}
\caption{The resulting parameters for variable stars studied}
%\label{vysledky_tab}
\begin{tabular}{lrcccllll}
\hline \hline
GCVS/IBVS & MS & $\alpha_{\rm 1950.0}$ & $\delta_{\rm 1950.0}$ &
$\Delta m_{\rm pg}$ & P [d] & $\rm T_{max}$ (JDhel.) & Type &  Note \\ \hline
V375 Cyg  &    &  20 45 32 & +35 42.1 & 11.9 - 14.6 & 335.9       & 2447395.0     &  SRA    & 1    \\
V384 Cyg  &    &  20 44 39 & +34 48.6 & 12.1 - 17.5 & 114.8-117.3 &       -       &  M      & 2    \\
V523 Cyg  &    &  21 00 04 & +35 06.9 & 11.6 - 18.0 & 379.4       & 2444458.4     &  M      & 3    \\
V1838 Cyg & 18 &  20 43 45 & +36 33.2 & 12.0 - 18.0 & 340.7       & 2443967.7     &  M      & 3    \\
V1854 Cyg & 38 &  20 46 17 & +36 41.5 & 13.4 - 15.5 & 106.5       & 2446240.0     &  SR     & 4    \\
V1856 Cyg & 40 &  20 46 21 & +35 16.1 & 13.0 - 15.7 & 1.999201    & 2448785.201   &  EA     & 3, 5 \\
V1863 Cyg & 51 &  20 47 42 & +37 02.6 & 13.3 - 15.5 & 7.322       & 2446499.7     &  CEP    & 4, 6 \\
V1864 Cyg & 53 &  20 48 09 & +37 18.9 & 14.3 - 18.0 & 463.2       & 2443494.3     &  M      & 3    \\
V1868 Cyg & 63 &  20 49 17 & +36 42.5 & 13.5 - 18.5 & 402.6       & 2443548.8     &  M      & 3    \\
V1871 Cyg & 66 &  20 49 42 & +35 05.9 & 12.5 - 15.6 & 692.5       & 2444262.0     &  M:     & 3, 6 \\
V1877 Cyg & 73 &  20 50 42 & +34 12.3 & 13.1 - 15.2 & 4.54091     & 2444183.904   &  CEP    & 4, 7 \\
V1886 Cyg & 83 &  20 54 16 & +36 10.3 & 13.4 - 15.6 & 254.8       & 2446140.0     &  SR     & 4, 7 \\
V1889 Cyg & 86 &  20 55 09 & +33 56.5 & 13.4 - 15.8 & 1.3311      & 2446092.26    &  CEP    & 6, 8 \\
V1894 Cyg & 95 &  20 58 43 & +33 53.3 & 12.1 - 13.4 & 257.8       & 2443749.0     &  M:     & 6, 8 \\
   -       & 8  &  20 41 03 & +35 19.3 & 12.1 - 13.7 & 0.2534      & 2446599.129   &  RR Lyr & 4, 7 \\
   -       & 91 &  20 57 29 & +36 26.6 & 12.4 - 15.4 & 0.345372    & 2447415.787   &  RR Lyr & 4, 7 \\
   -       & 99 &  21 03 03 & +35 28.1 & 13.9 - 16.7 &     -       &   -           &  SR     & 9    \\
\hline \hline
\\
\\
\multicolumn{9}{l}{{\it Notes to table 1}}\\
\multicolumn{9}{l}{1. the value of the period is close to the originally published one (Margoni {\it et al.}, 1989)}\\
\multicolumn{9}{l}{2. the value of the period  is changing in the interval indicated with a period of 16.3 years}\\
\multicolumn{9}{l}{3. accuracy of the value of the period has been improved}\\
\multicolumn{9}{l}{4. value of the period has been determined for the first time}\\
\multicolumn{9}{l}{5. epoch of minimum is presented}\\
\multicolumn{9}{l}{6. the original classification was not confirmed, a new type of variability was determined}\\
\multicolumn{9}{l}{7. type of variability has been determined for the first time}\\
\multicolumn{9}{l}{8. the originally determined value of the period was not confirmed, a new value of the period was determined}\\
\multicolumn{9}{l}{9. no unambiguous period could be determined}\\
\\
\multicolumn{9}{l}{For all the variable stars studied (except of V384 Cyg and MS99, with respect to the character of their }\\
\multicolumn{9}{l}{variability and the results found), new, more accurate values of the epoch of the extremum were determined}\\
\end{tabular}
\end{center}
\normalsize
\end{table*}

Table 1 summarizes the result of our study. The first two columns give the final designation according to the GCVS
and IBVS (Kholopov {\it et al.}, 1987 ) or the preliminary designation given by  Margoni and Stagni (1984).
We also present equatorial coordinates
for the equinox 1950.0 for each star, which is compatible with the GCVS.
The parameters of variability of these stars are further presented there:
the interval of light changes, the value of period, the epoch of maximum
(or minimum for the eclipsing binary) and the type of variability.
The note characterizes more closely the parameters obtained for the
individual variable stars investigated by us or describes the relation of the
results achieved by us to the results presented in the literature (GCVS,
Margoni and Stagni 1984 and Margoni {\it et al.} 1989).\\
\eject

Acknowledgements.
The authors wish to express their thanks to the Staff of the Asiago
Astrophysical Observatory for the provision of the original observational
material and for valuable advices during the measurement of the photographic
plates. This work has been supported through the Slovak Academy of Sciences
Grant No. 5016/98.
\\
\references

Andronov, I.L.: 1995, private comm.

Deeming, T.J.: 1975, {\it Astrophysics and Space Science}, {\bf 36}, 137

Kholopov, P.N., Samus', N.N., Frolov, M.S., Goranskij, V.P.,
Gorynya, N.A., Kireeva, N.N., Kukarkina, N.P., Kurochkin, N.E.,
Medvedeva, G.I., Perova, N.B., Shugarov, S.Yu.: 1985,
{\it General Catalogue of Variable Stars}, Nauka, Moscow

Kholopov, P.N.,Samus', N.N.,Kazarovets, E.V.,
Kireeva, N.N.: 1987, {\it Inf. Bull. Variable Stars}, No.\,3058

Kom\v{z}\'{\i}k, R.: 1995, private comm.

Kurtz, D.W.: 1985, {\it MNRAS}, {\bf 213}, 773

Margoni, R.: 1993, private comm.

Margoni, R., Stagni, R.: 1984, {\it Astron. Astrophys. Suppl. Ser.}
{\bf 56}, 87

Margoni, R., Stagni, R., Munari, U., Marton, S.: 1989, {\it Astron.
Astrophys. Suppl. Ser.}, {\bf 81}, 393

Stellingwerf, R.F.: 1978, {\it Astrophys. J.}, {\bf 224}, 953

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