[vsnet-preprint 32] IZ And preprint

[Taichi Kato <tkato>]

Dear Colleagues,

   The following article on IZ And is accepted for publication as IBVS 5102.

   The figures are available at:
   http://ftp.kusastro.kyoto-u.ac.jp/vsnet/preprints/IZ_And/

Regards,
Taichi Kato

===

\documentstyle[twoside,epsf]{article}

\input{ibvs2.sty}

\begin{document}

\IBVShead{xxxx}{xx May 2001}

\IBVStitletl{Outburst Photometry of IZ And}

\IBVSauth{Taichi~Kato$^1$}
\vskip 5mm

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

\IBVSobj{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 an 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.

\vskip 3mm

   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.

\vskip 3mm

   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 {\it 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.

\begin{table}
\begin{center}
Table 1. Nightly averaged magnitudes of IZ And \\
\vspace{10pt}
\begin{tabular}{ccccc}
\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}
\end{center}
\hskip 35mm $^a$ BJD$-$2400000

\hskip 35mm $^b$ Magnitude relative to GSC 2807.1784

\hskip 35mm $^c$ Standard error of nightly average

\hskip 35mm $^d$ Number of frames

\end{table}

\IBVSfig{10cm}{fig1.ps}{Light curve of the 1996 September outburst
of IZ And}

\vskip 3mm

   Figure 1 shows the overall light curve of the 1996 September outburst.
The object gradually faded, at a maximum rate of 0.48$\pm$0.11 mag d$^{-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 0.002 d and 0.1 d.  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}{fig2.ps}{Enlarged light curve of IZ And on 1996 September 15.
Only low-amplitude irregular variations were present.}

\references

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

Meinunger, L., 1975, MVS, 7, 1

Meinunger, L., Andronov, I. L., 1987, 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, Memoirs of the Faculty of Science, Kyoto University,
     Series A of Physics, Astrophysics, Geophysics and Chemistry,
     38, 167

Stepanian, J. A., 1982, Perem. Zvezdy, 21, 691

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

\end{document}

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