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\IBVShead{5078}{14 May 2001}

\IBVStitle{SU UM\lowercase{a}-type Dwarf Nova V369 P\lowercase{eg}}

\IBVSauth{Kato, Taichi; Uemura, Makoto}

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

\SIMBADobj{V369 Peg}
\IBVStyp{ UGSU }
\IBVSkey{dwarf nova}

\begintext

V369 Peg = NSV 26006 = KUV 23012+1702 was originally discovered
as a variable, ultraviolet-excess object (Kondo et al.\ 1984).  Wegner and
Dupuis (1993) took a low-resolution spectrum of this object and described
that ``H$\alpha$ and H$\beta$ look as if they have emission cores'', and gave
a spectroscopic classification of sdBe.  The variability of KUV 23012+1702
was studied on Moscow plates by Antipin (1998).  Antipin (1998) discovered
that the star is a dwarf nova with a variability range of 15.8--$<18.0$~p.
Antipin (1998) also noted the presence of two kinds of outbursts, bright
ones lasting more than 8 days and faint ones lasting less than 5 days.
KUV 23012+1702 was thus considered as a very good candidate for an
SU UMa-type dwarf nova.  This object received a GCVS designation of
V369 Peg (Kazarovets et al.\ 2000).

J. Pietz detected an outburst on 1999 November 3, and detected hump
features with an amplitude of 0\fmm35 from his November 4 CCD
observations (Pietz 1999).  We started time-series CCD observations
during this apparent superoutburst.

The CCD observations were done using an unfiltered ST-7 camera attached
to the Meade 25-cm Schmidt--Cassegrain telescope.  The exposure time
was 30 s.  The images were dark-subtracted, flat-fielded, and analyzed
using the Java$^{\rm TM}$-based PSF photometry package developed by one
of the authors (TK)\@.  The magnitudes were determined relative to GSC
1711.839 (Tycho-2 magnitude: $V=11.44\pm0.12$, $B-V=+0.87\pm0.26$), whose
constancy during the run was confirmed using GSC 1711.2320.  Table 1
summarizes the log of observations.  Barycentric corrections to the
observed times were applied before the following analysis.

\begin{table}
\caption{Nightly averaged magnitudes of V369 Peg}
\begin{center}
\begin{tabular}{ccllr}
\hline
JD start$^a$ & JD end$^a$ & mean mag$^b$ & error$^c$ & $N^d$ \\
\hline
51488.982 & 51489.125 & 4.294 & 0.045 & 160 \\
51489.994 & 51490.207 & 4.329 & 0.038 & 249 \\
51490.959 & 51491.206 & 4.486 & 0.043 & 164 \\
51492.020 & 51492.192 & 4.593 & 0.019 & 418 \\
51493.029 & 51493.181 & 4.586 & 0.022 & 378 \\
51496.031 & 51496.184 & 4.945 & 0.029 & 365 \\
51497.027 & 51497.156 & 4.987 & 0.042 & 265 \\
51499.031 & 51499.034 & -$^e$ & -     & 4 \\
51500.028 & 51500.133 & 5.336 & 0.531 & 52 \\
51501.028 & 51501.173 & 7.032 & 0.327 & 302 \\
51502.033 & 51502.064 & 8.818 & 1.611 & 80 \\
51503.135 & 51503.143 & 7.122 & 1.589 & 20 \\
51504.056 & 51504.061 & 9.8:  & 3.0   & 14 \\
51505.059 & 51505.163 & 6.736 & 1.205 & 9 \\
51507.003 & 51507.003 & -$^e$ & -     & 1 \\
51509.002 & 51509.005 & 5.955 & 0.276 & 10 \\
51510.996 & 51511.001 & -$^e$ & -     & 10 \\
51512.051 & 51512.055 & 9.120 & 2.081 & 11 \\
51513.038 & 51513.042 & 6.954 & 0.784 & 10 \\
51520.005 & 51520.009 & 8.084 & 1.083 & 10 \\
51521.001 & 51521.004 & -$^e$ & -     & 10 \\
51521.905 & 51521.994 & 5.112 & 0.092 & 17 \\
51522.968 & 51522.971 & 6.022 & 0.309 & 10 \\
51523.970 & 51523.974 & 7.211 & 0.699 & 11 \\
\hline
\end{tabular}

\normalsize
\begin{tabular}{r@{ }l}
$^a$ & JD${}-{}$2400000 \\
$^b$ & Magnitude relative to GSC 1711.839 \\
$^c$ & Standard error of nightly average \\
$^d$ & Number of frames \\
$^e$ & Object below detection limit (typically below 17\mm) \\
\end{tabular}
\end{center}
\end{table}

\IBVSfig{10cm}{5078-f1.ps}{Light curve of V369 Peg.  Relatively large
errors were caused by the faintness of the object}

\vskip-11pt
Figure 1 presents the overall light curve.  The figure shows a
long outburst (superoutburst) and following two short (normal) outbursts
occurring on JD 2451509 and JD 2451522.
The initial superoutburst detected by Pietz lasted until November 18,
followed by a rapid decline.  The duration of superoutburst was thus
15 days.  The interval of two subsequent normal outbursts was 13 days,
which can be regarded as the typical recurrence time of this dwarf nova.
The short recurrence time and the small outburst amplitude suggests
that the object is a rather active dwarf nova.

\IBVSfig{10cm}{5078-f2.ps}{Periodogram of V369 Peg}

\vskip-11pt
The data between JD 2451488 and 2451497 (superoutburst plateau),
after subtracting the linear trend of decline, were analyzed using
the Phase Dispersion Minimization (PDM) method (Stellingwerf 1978).
The resultant theta diagram is shown in Figure~2.  The best superhump
period is $0.08484\pm0.00010$ d.  The other one-day aliases were excluded
by independent detections of the same signal by Pietz (1999) and Vanmunster
(1999a, 1999b).  Figure~3 shows the phase-averaged light curve of superhumps.
The superhumps had a large amplitude of $\sim 0\fmm3$.
The superhump period of 0\fday0848 makes V369 Peg as one of SU UMa-type dwarf
novae with long orbital periods.  The overall pattern of outbursts looks
similar to the long-period system YZ Cnc.  Further detailed observations
are encouraged to precisely determine the system parameters.

\IBVSfig{10cm}{5078-f3.ps}{Superhump profile of V369 Peg}

The authors are grateful to VSNET members for notifying us of
outbursts, and exchanging timely information.

Part of this work is supported by a Research Fellowship of the Japan
Society for the Promotion of Science for Young Scientists (MU).

\references

Antipin, S. V., 1998, {\it IBVS}, No.\ 4578

Kazarovets, E. V., Samus, N. N., Durlevich, O. V., 2000, {\it IBVS},
No.\ 4870

Kondo, M., Noguchi, T., Maehara, H., 1984, {\it Ann. Tokyo Astron. Obs.}, {\bf 20}, 130

Pietz, J., 1999, {\it VSNET alert circulation}, No.\ 3665 (available
from\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert3000/msg00665.html)

Stellingwerf, R. F., 1978, {\it ApJ}, {\bf 224}, 953

Vanmunster, T., 1999a, {\it VSNET alert circulation}, No.\ 3680
(available from\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert3000/msg00680.html)

Vanmunster, T., 1999b, {\it VSNET alert circulation}, No.\ 3705
(available from\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert3000/msg00705.html)

Wegner, G., Dupuis, J., 1993, {\it AJ}, {\bf 106}, 390

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