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\begin{document}

\IBVShead{5102}{5 June 2001}

\IBVStitle{Outburst Photometry of IZ A\lowercase{nd}}

\IBVSauth{Kato, Taichi}

\IBVSinsto{Dept.\ of Astronomy, Kyoto University, Kyoto 606-8502, Japan,
e-mail: tkato@kusastro.kyoto-u.ac.jp}

\SIMBADobj{IZ And}
\IBVStyp{ UGSS }
\IBVSkey{dwarf nova, photometry}

\begintext

IZ And (= S 10794) is a dwarf nova discovered by Meinunger (1975),
who recorded two outbursts.  The object was later rediscovered by
Stepanian (1982), who spectroscopically observed one of its outburst,
and gave a classification as an O-B star.  This classification is
consistent with a low-resolution spectrum of dwarf nova at maximum.
Meinunger and Andronov (1987) reported another outburst detection,
and gave a discussion on its outburst cycle length.  The star, however,
has been largely neglected.

In the course of CCD survey of dwarf novae, the author detected another
outburst at $V=15.6$ on 1996 September 15.678 (Kato 1996).  We performed
time-resolved CCD photometry during this outburst.

The observations were done on three nights between 1996 September 15
and 17, using a CCD camera (Thomson TH~7882, $576 \times 384$ pixels,
on-chip $2 \times 2$ binning adopted) attached to the Cassegrain focus
of the 60-cm reflector (focal length${}=4.8$~m) at Ouda Station, Kyoto
University (Ohtani et al.\ 1992).  An interference filter was used
which had been designed to reproduce the Johnson $V$ band.  The
exposure time was 60 s.  The frames were first corrected for standard
de-biasing and flat fielding, and were then processed by a
microcomputer-based PSF photometry package developed by the author.
The magnitudes were determined relative to GSC 2807.1784 ($V=12.03$),
whose constancy during the run was confirmed using the check stars GSC
2807.1974 ($V=12.86$).  The magnitudes of comparison stars were
determined using the RX And sequence (Misselt 1996).  Barycentric
corrections to observed times were applied before the following
analysis.  Table 1 lists the log of observations, together with nightly
averaged magnitudes.

Figure 1 shows the overall light curve of the 1996 September outburst.
The object gradually faded, at a maximum rate of $0.48\pm0.11$ mag\,d$^{-1}$.
This rate of decline is a typical value for an SS Cyg-type dwarf nova.
Using Bailey's relation (e.g.\ Warner 1995), this rate of decline correspond
to an orbital period of 5~h.  Figure~2 shows the result of time-series
photometry on September 15.  Although there seem to exist low-amplitude
irregular variations (flickering), no evidence of superhumps was detected.
Power spectrum of the data did not reveal any significant periodicity
between 0\fday002 and 0\fday1.  The overall behavior is consistent with the
suggested orbital period from the decline rate, and supports the
classification as an SS Cyg-type (UGSS in GCVS) star.

\IBVSfig{10cm}{5102-f1.ps}{Light curve of the 1996 September outburst
of IZ And}

\IBVSfig{10cm}{5102-f2.ps}{Light curve of IZ And on 1996 September 15.
Only low-amplitude irregular variations were present}

\clearpage

\begin{table}
\begin{center}
\caption{Nightly averaged magnitudes of IZ And}
\begin{tabular}{ccccr}
\hline
start$^a$ & end$^a$ & mean mag$^b$ & error$^c$ & $N^d$ \\
\hline
50342.182 & 50342.297 & 3.509 & 0.010 & 145 \\
50343.127 & 50343.128 & 3.835 & 0.016 &   3 \\
50344.102 & 50344.104 & 4.312 & 0.112 &   3 \\
\hline
\end{tabular}

\normalsize
\begin{tabular}{l@{ }l}
$^a$ & BJD${}-{}$2400000 \\
$^b$ & Magnitude relative to GSC 2807.1784 \\
$^c$ & Standard error of nightly average \\
$^d$ & Number of frames \\
\end{tabular}
\end{center}
\end{table}

\references

Kato, T., 1996, {\it VSNET observations}, No.\ 3806 (available from \\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/obs3000/msg00806.html)

Meinunger, L., 1975, {\it MVS}, {\bf 7}, 1

Meinunger, L., Andronov, I. L., 1987, {\it IBVS}, No.\ 3081

Misselt, K. A., 1996, PASP, 108, 146

Ohtani, H., Uesugi, A., Tomita, Y., Yoshida,
M., Kosugi, G., Noumaru, J., Araya, S., Ohta, K.,
1992, {\it Memoirs of the Faculty of Science, Kyoto University,
Series A of Physics, Astrophysics, Geophysics and Chemistry},
{\bf 38}, 167

Stepanian, J. A., 1982, {\it Perem.\ Zvezdy}, {\bf 21}, 691

Warner, B., 1995, Cataclysmic Variable Stars (Cambridge Univ.\ Press.,
Cambridge)

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