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[vsnet-preprint 41] V363 Lyr preprint
Dear Colleagues,
The following article is accepted for publication as IBVS No. 5118.
The figures are available at:
http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/RX_Cha/
Regards,
Taichi Kato
===
\documentstyle[twoside,epsf]{article}
\input{ibvs2.sty}
\begin{document}
\IBVShead{xxxx}{xx May 2001}
\IBVStitle{Outburst cycle of V363 Lyr}
\IBVSauth{Kato,~Taichi$^1$, Nogami,~Daisaku$^{2,1}$, Baba,~Hajime$^{3,1}$, Masuda,~Seiji$^1$}
\vskip 5mm
\IBVSinst{Dept. of Astronomy, Kyoto University, Kyoto 606-8502, Japan,
e-mail: (tkato,masuda)@kusastro.kyoto-u.ac.jp}
\IBVSinst{Hida Observatory, Kyoto University, Gifu 506-1314, Japan,
e-mail: nogami@kwasan.kyoto-u.ac.jp}
\IBVSinst{Astronomical Data Analysis Center, National Astronomical
Observatory, Mitaka, Tokyo 181-8588, Japan,
e-mail: hajime.baba@nao.ac.jp}
\IBVSobj{V363 Lyr}
\IBVStyp{UGSS}
\IBVSkey{dwarf nova, photometry}
\begintext
V363 Lyr (=S 9653) is a dwarf nova discovered by Hoffmeister (1967).
Although the report by Hoffmeister (1967) suggested relatively frequent
outbursts, only a few studies were made since the discovery. Galkina and
Shugarov (1985) studied the variable photographically, and generally
confirmed the high outburst frequency suggested by Hoffmeister (1967).
However, the lack of dense coverage and non-detectability at minimum made
exact characterization of its outburst properties difficult. We therefore
made systematic CCD runs to clarify its outburst pattern.
\vskip 3mm
The observations were done on 57 nights between 1995 March 19 and 1996
September 5, 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--180 s, depending on the brightness of the object. 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 one
of the authors (TK). The magnitudes were determined relative to
GSC 3128.123 ($V$=14.26, VSNET chart), whose constancy during the run
was confirmed using GSC 3128.751. Barycentric corrections were applied
to the observed times before the following analysis. A total of 604 useful
frames were obtained. Since most of observations are nightly snapshots,
the log of observations is omitted.
\IBVSfig{8cm}{fig1.ps}{Overall light curve of V363 Lyr}
\vskip 3mm
Figure 1 shows the overall light curve of V363 Lyr. The high frequency
of outbursts and the high outburst duty cycle is already apparent.
The observed brightest maximum and faintest minimum was $V$=15.83 and
$V$=19.5$\pm$0.2, respectively. The maximum is in good agreement with the
GCVS value (15.7p), but the minimum can become slightly fainter than was
previously thought (18.6p).
\IBVSfig{8cm}{fig2.ps}{Typical outburst V363 Lyr}
\vskip 3mm
Figure 2 shows a typical, and the best observed, outburst of V363 Lyr,
which occurred in 1995 July -- August. The almost symmetrical rise and fade
are rather unusual for a dwarf nova. Table 1 lists the observed date
of maxima.
\begin{table}
\begin{center}
Table 1. Outbursts of V363 Lyr \\
\vspace{10pt}
\begin{tabular}{cc}
\hline
JD (maximum) & magnitude \\
\hline
2449796 & 16.12 \\
2449843 & 15.92 \\
2449932 & 16.01 \\
2449972 & 16.18 \\
2450292 & 15.83 \\
2450314 & 15.96 \\
\hline
\end{tabular}
\end{center}
\end{table}
\vskip 3mm
The shortest interval between outbursts was 22 d, which is in good
agreement with the interval observed in Hoffmeister (1967) and
Galkina and Shugarov (1985). Although there is an ambiguity of cycle
counts between JD 2449972 and 2450292, all the observed maxima are well
represented by $JD max = 2449799.7 + 21.446 \times E$ with $|O-C| < 4$ d.
A light curve folded by this period is shown in Figure 3. This figure
shows that the outburst pattern is relatively stable for a long time.
The existence of a number of scattered points deviating from the general
trend shows intrinsic variation from the semi-regular outburst pattern.
\IBVSfig{8cm}{fig3.ps}{Light curve of V363 Lyr folded by P=21.446 d}
\vskip 3mm
Such a stable light curve is rather unusual for a dwarf nova.
However, spectroscopic observation by Liu et al. (1998) confirmed the
dwarf nova-type nature of the object. The object may be a system with
high mass-transfer rate, showing regular outbursts and a slow rise
to outburst. Short-term variability was searched on 1995 March 20,
August 1--3 and 1996 July 27 (around maximum), and 1995 July 25--28
(near minimum), but did not yield a firm periodicity. A sample of
time-series observations (1996 July 27) is shown in Figure 4, which
did not reveal large-amplitude oscillations.
\IBVSfig{8cm}{fig3.ps}{Light curve of V363 Lyr on 1996 July 27}
\vskip 3mm
The authors are grateful to Mr. Ishida for helping the observation.
\references
Galkina, M. P., Shugarov, S. Yu., 1985, Perem. Zvezdy, 22, 225
Hoffmeister, C., 1967, AN, 289, 205
Liu, Wu., Hu, J. Y., Zhu, X. H., Li, Z. Y., 1998, ApJS, 122, 243
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
\end{document}
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