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\IBVShead{4463}{8 April 1997}

\title{A new suspected variable in Pisces}

\begintext

We report here of the finding of few brightenings of a star in the
neighbourhood of the irregular variable RZ Piscium.
We became aware of this behaviour during brightness estimates of
RZ Psc on sky patrol plates of the plate stacks of
the Harvard  College Observatory (Cambridge, MA, U.S.A.).


The presumed new variable was visible on only few plates. Normally
the magnitude  of the object in question was below the limiting
magnitude of the sky patrol plates.
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 Figure 1. Identification map for the presumed variable (Y) in the
neighbourhood of RZ Psc (RZ). Comparison stars are marked, too.
Their $ B $-magnitudes are listed in Table 1. The map covers an area of
26' ${ \times}$ 17' North is on the top and east to the left. The map is
based on a ${ \it B}$ plate obtained by R. Ziener, KSO, Tautenburg
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Plate flaws can be practically excluded as an explanation for the
sporadically appearing object since we found at the exact position
of it a faint star on a CCD image taken with the 90-cm
telescope of the Gro\ss schwabhausen (GSH) observing station  of the
Jena University Observatory. Independently, we identified the
star on prints of the Palomar Observatory Sky Survey as
well as on Schmidt plates in the plate archive of the Karl-
Schwarzschild-Observatory (KSO), Tautenburg.
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\centerline{Table 1. ${ \it B }$-magnitudes of the comparison stars }
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\begin{center}
\begin{tabular}{cc|cc}
\hline
Comparison   &     $ B $  & Comparison & $ B $  \\[-0.2cm]
star & (mag)            & star  &  (mag)    \\\hline
a   &  11.42  &       3   &    14.49   \\
b   &  12.28  &       4   &    14.84    \\
c   &  12.44  &       5   &    13.86   \\
d   &  12.95  &       6   &    14.00    \\
f   &  13.15  &       7   &    12.76    \\
x   &  14.08  &       8   &    14.34    \\
1   &  10.12  &       9   &    15.38    \\
2   &  12.25    && \\
\hline
\end{tabular}
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\centerline{Table 2. Brightnesses of star Y }
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 \begin{center}
 \begin{tabular}{lcc}
\hline
\noalign{\medskip}
Julian Date   &      Brightness     &   Remarks\\
              &        (mag)        &           \\
\noalign{\medskip}
\hline
 2427683.797  &  14.86   &    Harvard Obs., ${  B }$ \\
 2427692.805  &  14.86   &    Harvard Obs., ${  B }$ \\
 2427736.702  &   12.44  &    Harvard Obs., ${  B }$ \\
 2433237.500 &    $\approx$ 14.5 &    Harvard Obs., ${  B }$ \\
 2443417.368  &   $\approx$ 15.7  &    KSO, Tautenburg ${  B }$ \\
 2443417.380  &   $\approx$ 15.3  &    KSO, Tautenburg ${  V }$ \\
 2443417.392  &   $\approx$ 14.9  &    KSO, Tautenburg ${  R }$ \\
 2443840.292  &   $\approx$ 16.1  &    KSO, Tautenburg ${  B }$ \\
 2450347.421  &  16.17   &    GSH, CCD, ${  B }$ \\
\hline
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    \end{tabular}
  \end{center}
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The identification map (Figure 1) covers only a part of
that map for RZ Psc published by Friedemann et al. (1995). In
the map presented here the object in question, RZ Psc, and the
comparison stars are marked. Their $B $ magnitudes have
been derived on the blue CCD images obtained by us using
photometric standard stars measured  by Pugach and
Kovalchuk (1983) and Wenzel (1993). The relevant photometric
data are compiled in Table 1. The mean r.m.s. error amounts to
$\pm 0.06$~mag.

The data of the few discovered brightenings are collected in Table 2.
The estimated photometric uncertainties amount to
$\Delta  m \approx \pm 0.2\,{\rm mag}$.

Additional information have been obtained by measuring the
brightness of the star on $ B, V$ and  $ R$ plates
of the KSO. For this aim we used for the comparison stars
$ B $ and $R$  magnitudes from the USNO-SA1.0
catalogue by Monet et al. (1996) and $ V$ from the Guide Star
Catalog 1.1 (1992). From the three KSO plates obtained at JD
2443417 we derived  $ B, V$ and  $ R$ magnitudes amounting
to 15.7, 15.3, and 14.9, respectively.
Combination of the $ B, V$ and  $ R$ data results in a colour index
$(B - V)\approx$ 0.4 mag and $(V - R)\approx$ 0.4 mag.
These values correspond to an unreddened star of spectral
type F2 to F8.

 Taking the brightenings found
(see Table 2) as representative, the amplitude of the light
variation amounts to $\Delta  m_{B} \approx 3.7 \pm 0.4\,{\rm mag}$.
The amplitude derived from the few existing photometric data and
the distribution of the brightenings over the time are compatible with the assumption
that the variable probably belongs to the class of U Geminorum stars.
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Acknowledgement. The authors are indebted to Dr. I. Shapiro, Director of the Harvard
College Observatory, for the permission for using the plate
collection and Dr. Martha Hazen, Curator of the plate Collection,
for her kind support and hospitality during their stay.
Furthermore, the authors thank Dr. R. Ziener from the KSO, Thueringer
Landessternwarte Tautenburg, for making the Schmidt plates
available to them and Dr. S. Klose for scanning these plates.
The work was partially supported by the Deutsche
Forschungsgemeinschaft (Grant Fr 963-1).

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\beginauthors
\authorsrightcol
H.-G. REIMANN
C. FRIEDEMANN
Astrophysikalisches Institut und
Unversit\"ats-Sternwarte Jena,
Schillerg\"a\ss chen 2,
07745 Jena, Germany,
e-mail: rei@astro.uni-jena.de
\endauthors

\references

Friedemann C., G\"urtler J. Reimann H.--G., 1995, {\it A\&A}, {\bf 300}, 269

Guide Star Catalog 1.1, 1992, Association of Universities for Research in
 Astronomy, Inc. 

Monet, D., Bird, A., Canzian, B., Harris, H., Reid, N., Rhodes, A., Sell, S.,
 Ables, H., Dahn, C., Guetter, H., Henden, A., Leggett, S., Levison, H., 
 Luginbuhl, C., Martini, J., Monet, A., Pier, J., Riepe, B., Stone, R., Vrba, F., Walker, R., 1996, USNO-SA1.0, (edited by U.S. Naval Observatory, Washington DC)

Pugach, A.F., Kovalchuk, G.U., 1983, {\it Perem. Zvesdy},  {\bf 22}, 9

Wenzel W., 1993, Private communication


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