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[vsnet-preprint 38] V1113 Cyg preprint (cycle length)
Dear Colleagues,
The following article is accepted for publication as IBVS No. 5110.
The figures are placed at:
http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/V1113_Cyg-cycle/
Regards,
Taichi Kato
===
\documentstyle[twoside,epsf]{article}
\input{ibvs2.sty}
\begin{document}
\IBVShead{xxxx}{xx June 2001}
\IBVStitle{On the cycle lengths of V1113 Cyg}
\IBVSauth{Kato,~Taichi$^1$}
\vskip 5mm
\IBVSinst{Dept. of Astronomy, Kyoto University, Kyoto 606-8502, Japan,
e-mail: tkato@kusastro.kyoto-u.ac.jp}
\IBVSobj{V1113 Cyg}
\IBVStyp{UGSU}
\IBVSkey{dwarf nova}
\begintext
V1113 Cyg is an SU UMa-type dwarf nova, whose nature was revealed
by Kato et al. (1996). In spite of its very usual appearance of superhumps
and their development, Kato et al. (1996) discussed that V1113 Cyg
has slightly different properties from those of other well-known
SU UMa-type dwarf novae: the short recurrence time ($\sim$10 d)
as inferred from the discovery observation by Hoffmeister (1966)
contradicts with the large outburst amplitude ($\sim$6 mag).
Kato et al. (1996) proposed the possible presence of active and inactive
phases, but further observations were undoubtedly needed to draw a
more definite conclusion. Since the discovery of its SU UMa-type nature,
the object has been well monitored by visual observers, as a part
of VSNET Collaboration (http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/).
A total of 992 observations were reported between 1994 July 15 and
2001 May 31, the rate corresponding to one observation per 2.5 d.
The number of positive detections was 149, corresponding to the
outburst duty cycle of 15\%. However, this value may have suffered
some degree of bias, since not all observations were made irrespective
of the outburst state. However, thanks to the dense coverage by these
observations, the selection of outbursts and its classification can be
almost always unambiguously done. The result is summarized in Table 1
and Figure 1.
\vskip 3mm
As is always evident from the table, almost all superoutbursts were
detected since 1994 July. The intervals of successive superoutbursts
relatively strongly varied between 169 and 229 d (during the 404 d
interval between JD 2451124 and 2451528, one superoutburst was likely
to be missed), 189.8 d in average. A noteworthy feature is the low
number ratio of (normal outbursts)/(superoutbursts). The total number
of observed outbursts is 30, while 12 of them are superoutbursts.
The number ratio suggests only two normal outbursts in each supercycle.
This ratio is very low for an SU UMa-type dwarf nova with the short
supercycle of 189.8 d (cf. Nogami et al. 1997). In order to estimate
the possibility of missed outbursts, owing to the observational gaps,
we applied Monte-Carlo simulations on actual observations. $\sim$50\%
of simulated normal outbursts were detected using the actual timings
of observations. The reduced detectability is mainly caused by the
observational gaps, and not by limiting magnitudes. Even though this
detectability of normal outbursts would raise the number ratio to $\sim$4,
this is still small for a system with a short supercycle.
\vskip 3mm
We know another example, V503 Cyg, which normally shows only 2--3 normal
outbursts in one 89-d supercycle (Harvey et al. 1995; Ishioka et al.
in preparation). There should be a still poorly understood mechanism
common to these objects, which suppresses normal outburst while maintaining
a high frequency of superoutbursts. A notable exception can be found
after the JD 2451716 superoutburst. The shortest interval between normal
outburst was 21 d. Since the object was equally frequently and deeply
monitored in the preceding season, this increased detections may actually
reflect the increased activity of this star. This phenomenon, if confirmed,
would provide a support to the idea of active and inactive phases,
proposed by Kato et al. (1996).
\begin{table}
\begin{center}
Table 1. Outbursts of V1113 Cyg \\
\vspace{10pt}
\begin{tabular}{cccc}
\hline
JD start & peak magnitude & duration (d) & type \\
\hline
2449597 & 13.3 & 15 & super \\
2449826 & 13.5 & $>$4 & super \\
2449893 & 13.9 & 3 & normal \\
2449956 & 13.8 & 3 & normal \\
2450025 & 13.4 & 11 & super \\
2450203 & 13.6 & $>$8 & super \\
2450280 & 13.8 & 2 & normal \\
2450308 & 14.0 & 1$^a$ & normal \\
2450333 & 13.8 & 2 & normal \\
2450372 & 13.4 & $>$6 & super \\
2450420 & 13.9 & 1$^a$ & normal \\
2450546 & 13.9 & 11 & super \\
2450689 & 13.8 & 2 & normal \\
2450728 & 13.7 & 11 & super \\
2450816 & 14.0 & 2 & normal \\
2450929 & 13.9 & $>$8 & super \\
2450956 & 15.2 & 1$^a$ & normal \\
2450999 & 14.4 & 1$^a$ & normal \\
2451037 & 14.8 & 2 & normal \\
2451124 & 13.8 & $>9$ & super \\
2451296 & 13.9 & 2 & normal \\
2451367 & 14.5 & 2 & normal \\
2451528 & 13.8 & $>$4 & super \\
2451664 & 14.1 & 3 & normal \\
2451716 & 13.5 & 12 & super \\
2451746 & 14.7 & 2 & normal \\
2451818 & 14.9 & 2 & normal \\
2451839 & 13.9 & 3 & normal \\
2451902 & 13.7 & $>$2 & super? \\
2452025 & 14.0 & 3 & normal \\
\hline
\end{tabular}
\end{center}
\hskip 45mm $^a$ single observation
\end{table}
\IBVSfig{10cm}{fig1.ps}{Overall light curve of V1113 Cyg. Superoutbursts
are marked with ticks. Upper limit observations are not plotted for
simplicity.}
\vskip 3mm
The authors are grateful to VSNET members, especially to Gary Poyner,
Tonny Vanmunster, Maciej Reszelski, Eric Broens, Hazel McGee, Jochen Pietz,
Mike Simonsen, Lasse T. Jensen and a number of observers for providing
crucial observations.
\references
Harvey, D., Skillman, D. R., Patterson, J., Ringwald, F. A., 1995
PASP, 107, 551
Hoffmeister, C., 1966, AN, 289, 139
Kato, T., Nogami, D., Masuda, S., Hirata, R., 1996, PASJ, 48, 45
Nogami, D., Masuda, S., Kato, T., 1997, PASP, 109, 1114
\end{document}
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