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[vsnet-preprint 19] V369 Peg = NSV26002 = KUV23012+1702 paper
V369 Peg = NSV26002 = KUV23012+1702 paper
Dear Colleagues,
The following article is accepted for publication as IBVS No. 5077.
The figures are placed at:
http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/V369_Peg/
Regards,
Taichi Kato
==========================================================================
\documentstyle[twoside,epsf]{article}
\input{ibvs2.sty}
\begin{document}
\IBVShead{xxxx}{xx May 2001}
\IBVStitletl{SU UMa-Type Dwarf Nova V369 Peg}
\IBVSauth{Taichi~Kato$^1$, Makoto~Uemura$^1$}
\vskip 5mm
\IBVSinst{Dept. of Astronomy, Kyoto University, Kyoto 606-8502, Japan,
e-mail: tkato@kusastro.kyoto-u.ac.jp,\\
uemura@kusastro.kyoto-u.ac.jp}
\IBVSobj{V369 Peg}
\IBVStyp{UGSU}
\IBVSkey{dwarf nova}
\begintext
V369 Peg = NSV 26002 = 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-$<$18.0p.
Antipin (1998) also noted the presence of two kinds of outbursts, bright
ones lasting more than 8 days and faint ones lasting less than 5 days.
KUV 23012+1702 was thus considered as a very good candidate for an
SU UMa-type dwarf nova. This object received a GCVS designation of
V369 Peg (Kazarovets et al. 2000).
\vskip 3mm
J. Pietz detected an outburst on 1999 November 3, and detected
hump features with an amplitude of 0.35 mag from his November 4
CCD observations (Pietz 1999). We started time-series CCD observations
during this apparent superoutburst.
\vskip 3mm
The CCD observations were done using an unfiltered ST-7 camera attached to
the Meade 25-cm Schmidt-Cassegrain telescope. The exposure time was 30 s.
The images were dark-subtracted, flat-fielded, and
analyzed using the Java$^{\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}
\begin{center}
Table 1. Nightly averaged magnitudes of V369 Peg \\
\vspace{10pt}
\begin{tabular}{ccccc}
\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}
\end{center}
\hskip 35mm $^a$ JD$-$2400000
\hskip 35mm $^b$ Magnitude relative to GSC 1711.839
\hskip 35mm $^c$ Standard error of nightly average
\hskip 35mm $^d$ Number of frames
\hskip 35mm $^e$ Object below detection limit (typically below mag 17)
\end{table}
\IBVSfig{8cm}{fig1.ps}{Overall light curve of V369 Peg. Relatively large
errors were caused by the faintness of the object.}
\vskip 3mm
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{8cm}{fig2.ps}{Period analysis of V369 Peg}
\vskip 3mm
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$0.3 mag.
The superhump period of 0.0848 d makes V369 Peg as one of SU UMa-type dwarf
novae with long orbital periods. The overall pattern of outbursts looks
similar to a long-period system YZ Cnc. Further detailed observations
are encouraged to precisely determine the system parameters.
\IBVSfig{8cm}{fig3.ps}{Superhump profile of V369 Peg}
\vskip 3mm
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, IBVS No. 4578
Kazarovets, E. V., Samus, N. N., Durlevich, O. V., 2000, IBVS No. 4870
Kondo, M., Noguchi, T., Maehara, H., 1984, {\it Ann. Tokyo Astron. Obs.},
20, 130
Pietz, J., 1999, {\it VSNET alert circulation}, No. 3665 \\
(available from
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert3000/msg00665.html).
Stellingwerf, R. F., 1978, ApJ, 224, 953
Vanmunster, T., 1999a, {\it VSNET alert circulation}, No. 3680 \\
(available from
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert3000/msg00680.html).
Vanmunster, T., 1999b, {\it VSNET alert circulation}, No. 3705 \\
(available from
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert3000/msg00705.html).
Wegner, G., Dupuis, J., 1993, AJ, 106, 390
\end{document}
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