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\IBVShead{4307}{13 March 1996}

\centerline{\ft  NEW TIMES OF MINIMA OF THE ECLIPSING} 
\centerline{\ft BINARIES 44i BOOTIS AND VW CEPHEI}
\vskip 6mm

\begintext

             The eclipsing variable stars 44i Boo and VW Cep are two
         well observed active  close  binaries  of W UMa type.  Here, we
         present  new times  of minima  for these two systems
         determined from our photoelectric observations made during
         1995.
\vskip 2mm
\underline{44i Bootis}
\vskip 2mm         
    The eclipsing binary 44i Boo is the fainter companion (B+C)
         of the close visual binary ADS 9494. Its light curves are
         characterized by ``active" and ``quiet" intervals and its period
         is variable (e.g. Bergeat et al., 1972; Rovithis and Rovithis-Livaniou,                              1990, Oprescu et al., 1989 \& 1991; Gherega et al., 1994).

             New  photoelectric  observations of  the  system  were made
         during two nights in April, as well as during one in May and
         two in August 1995. The observations in April were made with
         the two-beam, multi-mode, nebular-stellar photometer of the
         National Observatory  of Athens,  attached  to the 48-inch
         Cassegrain reflector at the Kryonerion Astronomical Station;
         while, those in May and August with an EMI 9502\,B type
         photocell, attached to the 50cm Cassegrain telescope of the
         Bucharest Observatory.

             From our observations of 44i Boo six  new minima times
         were derived and are presented in Table I.
\vskip 2mm
\centerline{Table 1. Photoelectric minima of 44i Bootis}
\vskip 1mm
\begin{center}
\begin{tabular}{rlcccc}
\hline
 Hel JD   &   Min & Filter&   (O$-$C)$_I$ &    (O$-$C)$_{II}$ &    (O$-$C)$_{III}$\\
 2440000+ &        &          & days      &          days     &   days\\
\hline
           9812.4825   &  II   &  V    &  0.0528   &  0.0155 &    $-$0.0068\\
               .4827   &  II   &  B    &  0.0530   &  0.0157 &    $-$0.0066\\
               .6152   &  I    &  V    &  0.0516   &  0.0143 &    $-$0.0080\\
               .6148   &  I    &  B    &  0.0512   &  0.0139 &    $-$0.0084\\
           9813.4184   &  I    &  V    &  0.0513   &  0.0140 &    $-$0.0073\\
               .4188   &  I    &  B    &  0.0517   &  0.0144 &    $-$0.0069\\
           9866.4487   &  I    &  V    &  0.0541   &  0.0164 &    $-$0.0051\\
               .4468   &  I    &  B    &  0.0522   &  0.0145 &    $-$0.0070\\
               .4471   &  I    &  U    &  0.0525   &  0.0148 &    $-$0.0067\\
           9938.3678   &  II   &  V    &  0.0646   &  0.0265 &    +0.0048\\
               .3683   &  II   &  B    &  0.0651   &  0.0270 &    +0.0053\\
               .3646   &  II   &  U    &  0.0614   &  0.0233 &    +0.0016\\
           9943.3130   &  I    &  V    &  0.0552   &  0.0171 &    $-$0.0047\\
               .3128   &  I    &  B    &  0.0550   &  0.0169 &    $-$0.0049\\
               .3139   &  I    &  U    &  0.0561   &  0.0180 &    $-$0.0038\\
\hline
\end{tabular}
\end{center}
\vskip 2mm        

              In Table 1 the residuals (O$-$C)$_I$, (O$-$C)$_{II}$ \& (O$-$C)$_{III}$ have
         been calculated using Kwee \& Van Woerden's method  (1956) and
         according to the following ephemeris formulae:


        \vfill \eject

\centerline{2}
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\centerline{\epsffile{4307-f1.ps}}
\begin{center}
Figure 1. The latest part of the (O$-$C) diagram of 44i Boo, based on Duerbeck's (1975)
ephemeris formula.
\end{center}

\epsfysize=10cm
\centerline{\epsffile{4307-f2.ps}}
\begin{center}
Figure 2. The latest part of the (O$-$C) diagram of VW Cep, based on Navratil's (1994)
ephemeris formula.
\end{center}
\vfill \eject

\centerline{3}

\vskip 1mm
\hspace*{3.3cm}(I):   Min I = J.D.\,2439852.4903 + 0.2678159 $\times$ E  

\centerline{(Duerbeck, 1975)}
\vskip 2mm
        \hspace*{3cm} (II):  Min I = J.D.\,2439852.4644 + 0.2678176 $\times$ E 

\centerline{(Rovithis and Rovithis-Livaniou, 1990)}
\vskip 2mm
       \hspace*{2.9cm} (III): Min I = J.D.\,2443604.5880 + 0.26781856 $\times$ E 

\centerline{(Oprescu et al., 1991)}

\vskip 2mm
             From the recent part of the O$-$C  diagram of  44i Boo,  which is
         presented in  Figure 1  -- based on Duerbeck's (1975) ephemeris
         and corresponding to the last years --  and from a comparison of
         the O$-$C values presented in Table 1, with those of
         Rovithis-Livaniou et al.  (1995),   we can  see  that  the period  of
         44i Boo is continuously increasing.

\vskip 2mm
          \underline{VW Cephei}
\vskip 2mm
         The eclipsing binary  VW Cep is a member of a triple system
         (Hershey, 1975).  Its light curves  show  temporal  variation
         on short time scales  (from night to night;  e.g. Kwee, 1966;
         Kreiner \& Winiarski, 1981), as well as on long time scales (e.g.
         Karimie, 1983; Kotarska \& Glownia, 1983; Bradstreet \& Guinan,
         1990).

             Photoelectric observations of  VW Cep were made during nine
         nights (1 in August,  3 in September and  5 in October
         1995), at the Bucharest  Observatory  using the  same
         instruments as for the observations of 44i Bootis.

\vskip 4mm

\centerline{Table 2. New minima of VW Cephei}
\begin{center}
\begin{tabular}{rlclcc}
\hline
 Hel.JD   &  Min. &  Filter   &  E    &   (O$-$C)$_I$  &    (O$-$C)$_{II}$\\
 2400000+ &  Type    &             &   &   days   &     days\\
\hline
\\        
        49953.3496 &    II  &   V &     3919.5 &   $-$0.0299 &    +0.0010\\
             .3473 &    II  &   B &            &   $-$0.0322 &    $-$0.0013\\
             .3431 &    II  &   U &            &   $-$0.0364 &    $-$0.0055\\
             .4851 &    I   &   V &     3920   &   $-$0.0336 &    $-$0.0026\\
             .4843 &    I   &   B &            &   $-$0.0344 &    $-$0.0034\\
             .4862 &    I   &   U &            &   $-$0.0325 &    $-$0.0015\\
        49975.3304 &    II  &   V &     3998.5 &   $-$0.0360 &    $-$0.0045\\
             .3324 &    II  &   B &            &   $-$0.0340 &    $-$0.0025\\
             .3316 &    II  &   U &            &   $-$0.0348 &    $-$0.0033\\
        49994.2599 &    II  &   V &     4066.5 &   $-$0.0319 &    +0.0001\\
             .2600 &    II  &   B &            &   $-$0.0318 &    +0.0002\\
             .2558 &    II &    U &            &   $-$0.0360 &    $-$0.0040\\
        49996.3481 &    I &     V &     4074   &   $-$0.0310 &    +0.0010\\
             .3472 &    I &     B &            &   $-$0.0319 &    +0.0001\\
             .3475 &    I  &    U &            &   $-$0.0316 &    +0.0004\\
        50003.3057 &    I &     V &     4099   &   $-$0.0313 &    +0.0017\\
             .3067 &    I &     B &            &   $-$0.0303 &    +0.0027\\
             .3034 &    I &     U &            &   $-$0.0336 &    $-$0.0006\\
        50004.2770 &    II&     V &     4102.5 &   $-$0.0340 &    $-$0.0000\\
             .2758 &    II&     B &            &   $-$0.0352 &    $-$0.0022\\
             .2775 &    II&     U &            &   $-$0.0335 &    $-$0.0005\\
    \hline
\end{tabular}
\end{center}
\vfill \eject

\centerline{4}
\vskip 1mm
     From our observations seven new minima times were derived
         and are presented in Table 2; where the residuals have been
         found using Kwee \& Van Woerden's method  (1956)  and the  C's
         have been calculated according to the ephemeris:

\hspace*{3cm} Min I = J.D.\,2448862.5255 + 0.27831460 $\times$  E   \hfill    (I)
 \centerline{(Navratil, 1994)}

\noindent and its improvement:
\vskip 1mm
\hspace*{3cm} Min I = J.D.\,2448862.5220 + 0.2783076 $\times$ E  \hfill      (II)
\centerline{(Aluigi et al., 1994)}



         From the recent part the O$-$C diagram of VW Cep, presented in
         Figure 2 -- correspond\-ing to the last years and based on Aluigi
         et al.'s  (1994)  ephemeris --  it is clear  that  the  orbital
         period of the system is decreasing.



          Moreover, from the O$-$C values of Table 2, one can notice
         that better results  are obtained from the improved ephemeris
         -- that of  Navratil's  (1994) --  which  corresponds  to  a
         smaller period for VW Cep,  indicating  again that the period
         of the system is continuously decreasing.

         Acknowledgements: This work  was partly financially supported
         by a bilateral  Greek-Romanian  cooperation  program  of  the
         Ministry of Industry, Energy and Technology.
\vskip .6cm

\beginauthors
G. OPRESCU           
A. DUMITRESCU          
Astron. Inst.          
Bucharest Obs.        
Bucharest, Romania 
\vskip 2.5cm               
\authorsrightcol
P. ROVITHIS
Astron. Inst.
Athens National Obs.
Athens, Greece
\vskip 2mm
H. ROVITHIS-LIVANIOU
Section of Astroph.
Astron. \& Mechanics
Dept. of Physics
Athens University, Greece
e-mail: elivan@atlas.uoa.gr
\endauthors
\vskip -3mm
\references

Aluigi, M., Galli, G. \& Gaspani, A., 1994, {\it IBVS}. No.\,4117

Bergeat, J., Lunel, M. \& Van't Veer\ F., 1972, {\it A\&A}, {\bf 17}, 215

Bradstreet, D. \& Guinan, E., 1990, in ``Active Close Binaries",
               (Ed. C. Ibanoglu), Kluwer, p. 467

Duerbeck, H.W., 1975, {\it IBVS}, No.\,1023

Gherega, O., Farkas, L. \& Horv\'ath, A., 1994, {\it IBVS},  No.\,4045

Hershey, J.L., 1975, {\it ApSS}, {\bf 36}, 137

Karimie, M.T., 1983, {\it ApSS}, {\bf 92}, 53

Kotarska, I. \& Glownia, Z., 1983, {\it AN}, {\bf 304}, 181

Kreiner, J.M. \& Winiarski, M., 1981, {\it Acta Astron.}, {\bf 31}, 351

Kwee, K.K., 1966, {\it Bull. A. I. Neth.}, {\bf 18}, 448

Kwee, K.K. \& Van Woerden, H., 1956, {\it Bull. A. I. Neth.}, {\bf 12}, 327

Navratil, M., 1994, {\it IBVS}, No.\,3997

Oprescu, G., Suran, M.D. \& Popescu, N., 1989, {\it IBVS}, No.\,3368

Oprescu, G., Suran, M.D. \& Popescu, N., 1991, {\it IBVS}, No.\,3560

Rovithis,  P. \& Rovithis-Livaniou, H., 1990, {\it A\&ASS}, {\bf 86}, 523

Rovithis-Livaniou, H., Rovithis, P., Oprescu, G. \& Dumitrescu, A.,
                 1995, {\it IBVS}, No.\,4172

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