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\IBVShead{4332}{26 April 1996}

\title{v470 cassiopeiae is an rr lyrae type variable}
\vspace{-1em}
\centerline{[BAV Mitteilungen Nr.\,87]}
\vskip 8mm

\begintext

V470~Cas = S8459~Cas was discovered by Hoffmeister (1964) on
photographic plates of the Sonneberg Observatory. He classified this
star as a short period variable in the range between 12\fm5 and 13\fmm,
possibly eclipsing. First investigation of this variable was performed
by Meinunger (1968). She determined the range of variability between
13\fm0 to 13\fm5 and gave first elements as:
\vskip 1mm
\hspace*{3cm}Min\,I = HJD\,2429231.369 + 0\fd444692 $\times$ E \hfill (1)
\vskip 1mm


V470~Cas was cited again as eclipsing variable in a paper by Gessner
and Meinunger (1973), in which the authors note that the investigation
of this variable was handicapped by its relative high brightness and 
small amplitude. They gave eight times of minima and mentioned that the
above elements may not be regarded as ascertained.
With these data V470 Cas is listed in the fourth edition of the GCVS
(Kholopov et al., 1985).

For a quarter of a century the variable had not been observed, when we put
V470 Cas on our observing program. The CCD observations were made with
SBIG ST6 cameras without filters, attached to a 32cm RC telescope
(W.M.) and a 20cm SC telescope (F.A.). GSC\,3678.1232 (11\fm84) served
as comparison star.

A period analysis program, based on the algorithm of 
Schwarzenberg-Czerny (1989) resulted in a period roughly double as
long as the GCVS period. As our CCD observations show, the variable is
of RR~Lyr type with a rather long period and small amplitude. In our
instrumental system the amplitude of variability is 0\fm35 and M$-$m =
0\fp35.

To expand our knowledge of period changes to the past, one of us
(E.S.) investigated this star on 721 plates of the Sonneberg Sky
Patrol.

The timespan covered by these plates (1957 -- 1993) was divided into
several parts. Using a first ephemeris, for each of these parts a mean
lightcurve was calculated and the time of the normal maximum was
derived (W.K., see Table 1). From that, 23 moments of normal maximum
light resulted. The O$-$C residuals are shown plotted in Figure 2.

Obviously the period did not remain constant in the investigated
interval of time. Considering the accuracy of estimates on
photographic plates the period probably changed at about JD\,2445000.

Least squares fits in each of these intervals  yield the following linear elements:
\vskip 1mm
\hspace*{3cm}Max\,I = HJD\,2436200.588 + 0\fd 874356 $\times$ E \hfill (2)
\hspace*{7.5cm}$\pm$25 \hspace*{15mm}$\pm$5

\centerline{(valid between JD\,2436200 and JD\,2445000), and}

\vfill \eject

\centerline{2}
\vskip 1mm


\begin{center}
Table 1. Times of maxima for V470~Cas,
 epochs and residuals computed with respect to the ephemeris (3)
 derived in this paper
\end{center}
\vskip 1mm
\begin{center}
\begin{tabular}{rlrlrlc}
\hline 
 N & JD hel. & W & T$^{\star}$ &Epoch &O$-$C & Observer \\
  & 2400000+ &   &             &      &      &          \\
\hline
\\
   1 & 36200.613 &  2 &   P   &  $-$14833 &    +1.040  & [1] \\
   2 & 37558.455 &  2 &   P   &  $-$13280 &    +0.838  & [1] \\
   3 & 37871.528 &  2 &   P   &  $-$12922 &    +0.852  & [1] \\
   4 & 38233.474 &  2 &   P   &  $-$12508 &    +0.769  & [1] \\
   5 & 38413.621 &  2 &   P   &  $-$12302 &    +0.776  & [1] \\
   6 & 38974.812 &  2 &   P   &  $-$11660 &    +0.561  & [1] \\
   7 & 39765.286 &  2 &   P   &  $-$10756 &    +0.518  & [1] \\
   8 & 40318.762 &  2 &   P   &  $-$10123 &    +0.457  & [1] \\
   9 & 41192.386 &  2 &   P   &  $-$9124 &    +0.490  & [1] \\
  10 & 41897.052 &  2 &   P   &   $-$8318 &    +0.337  & [1] \\
  11 & 42631.510 &  2 &   P   &   $-$7478 &    +0.244  & [1] \\
  12 & 43431.382 &  2 &   P   &   $-$6563 &    $-$0.020  & [1] \\
  13 & 44816.563 &  2 &   P   &   $-$4979 &    +0.008  & [1] \\
  14 & 45204.812 &  2 &   P   &   $-$4535 &    $-$0.005  & [1] \\
  15 & 46271.676 &  2 &   P   &   $-$3315 &    +0.011  & [1] \\
  16 & 46648.542 &  2 &   P   &   $-$2884 &    $-$0.018  & [1] \\
  17 & 46763.152 &  2 &   P   &   $-$2753 &    +0.037  & [1] \\
  18 & 47392.762 &  2 &   P   &   $-$2033 &    +0.032  & [1] \\
  19 & 47776.617 &  2 &   P   &   $-$1594 &    $-$0.003  & [1] \\
  20 & 47939.302 &  2 &   P   &   $-$1408 &    +0.031  & [1] \\
  21 & 48503.249 &  2 &   P   &   $-$763 &    $-$0.052  & [1] \\
  22 & 48600.399 &  2 &   P   &   $-$652 &    +0.032  & [1] \\
  23 & 48862.626 &  2 &   P   &    $-$352 &    $-$0.080  & [1] \\
  24 & 49170.529 & 60 &   E   &       0 &    +0.011  & [2] \\
  25 & 49213.36  & 30 &   E:  &      49 &    $-$0.01   & [2] \\
  26 & 49226.467 & 60 &   E   &      64 &    $-$0.017  & [2] \\
  27 & 49588.520 & 30 &   E:  &     478 &    +0.008  & [3] \\
  28 & 49644.491 & 30 &   E:  &     542 &    +0.013  & [3] \\
  29 & 49658.5005& 60 &   E   &     558 &    +0.0308 & [2] \\
  30 & 49659.3690& 60 &   E   &     559 &    +0.0248 & [2] \\
  31 & 49693.478 & 60 &   E   &     598 &    +0.030  & [3] \\
  32 & 49978.561 & 30 &   E:  &     924 &    +0.037  & [3] \\
  33 & 49979.449 & 60 &   E   &     925 &    +0.051  & [3] \\
  34 & 50013.525 & 60 &   E   &     964 &    +0.022  & [3] \\
\hline
\end{tabular}
\end{center}
\vskip 2mm

$^{\star})$ E denotes CCD observed maxima, P are photographic.
Those marked with  

`:' got reduced weight.

\vskip 3mm
[1]: E. Splittgerber, W. Kleikamp,
[2]: W. Moschner,
[3]: F. Agerer

\vfill \eject

\centerline{3}
\vskip 1mm
\epsfysize=9cm
\centerline{\epsffile{4332-f1.ps}}
\begin{center}
Figure 1: Differential light curve of V470~Cas with
respect to the new ephemeris (3).
\end{center}
\epsfysize=9cm
\centerline{\epsffile{4332-f2.ps}}
\begin{center}
Figure 2. O$-$C diagram for V470 Cas computed with respect to Max =
HJD\,2449170.518 + 0.8744654 $\times$ E using all available maximum 
timings. $\bullet$ represents photoelectric and \raisebox{0.3ex}{$_\Box$}
photographic normal maxima.
\end{center}
\vfill \eject

\centerline{4}
\vskip 1mm
\vskip 2mm
\hspace*{3cm}Max\,I = HJD\,2449170.518 + 0\fd 8744654 $\times$ E \hfill (3)
\hspace*{7.7cm}$\pm$1 \hspace*{15mm}$\pm$14

\centerline{(valid after JD\,2445000)}


\vskip 1cm
\beginauthors
\authorsrightcol
 F.~AGERER
 W.~KLEIKAMP
 W.~MOSCHNER
 E.~SPLITTGERBER
 Bundesdeutsche Arbeitsge\-mein\-schaft
 f\"ur Ver\"anderliche Sterne e.V. (BAV)
 Munsterdamm 90,
 D-12169 Berlin, Germany
\endauthors

\references

 Gessner, H., Meinunger, I., 1973, {\it Ver\"off. Sternw. Sonneberg},
     {\bf 7}, 6, 606

 Hoffmeister, C., 1964, {\it Astr. Nachr.},  {\bf 288}, 49

 Kholopov,  P.N.~et  al., 1985, Gen. Cat. of Var. Stars, $4^{\rm th}$\ Ed.,
     Nauka, Moscow

 Meinunger, I., 1968, {\it Mitt. Ver. Sterne (Sonneberg)}, {\bf 5}, 12 

 Schwarzenberg-Czerny, A., 1989, {\it Mon. Not. R. Astr. Soc.},
 {\bf 241}, 153
\end{document}
 
 
