[Message Prev][Message Next][Thread Prev][Thread Next][Message Index][Thread Index]
[vsnet-preprint 8] SS UMi supercycle paper
SS UMi supercycle paper
Dear Colleagues,
The following paper will appear as IBVS No. 4932. Another IBVS paper
purely based on visual observations!
The figures are under (sorry they are still in .ps)
http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/SS_UMi_cycle/
---
\documentstyle[twoside, epsf]{article}
\input{ibvs2.sty}
\begin{document}
\IBVShead{xxxx}{xx June 2000}
\IBVStitletl{Detection of Supercycle in SS UMi:}{Normal SU UMa-type Dwarf Nova with the Shortest Supercycle}
\IBVSauth{Taichi~Kato$^1$, Gene~Hanson$^2$, Gary~Poyner$^3$,
Eddy~Muyllaert$^4$, Maciej~Reszelski$^5$, Pavol~A.~Dubovsky$^6$}
\vskip 5mm
\IBVSinst{Dept. of Astronomy, Kyoto University, Kyoto 606-8502, Japan,
e-mail: tkato@kusastro.kyoto-u.ac.jp}
\IBVSinst{AAVSO, 4916 E. Palo Brea Ln., Cave Creek, AZ 85331, USA
e-mail: GeneHanson@aol.com}
\IBVSinst{BAA Variable Star Section,
67 Ellerton Road, Kingstanding, Birmingham B44 0QE, England
e-mail: gp@star.sr.bham.ac.uk}
\IBVSinst{VVS Belgium - Werkgroep Veranderlijke Sterren,
Eksterstraat 6, 8400 Oostende, Belgium
e-mail: eddy.muyllaert@ping.be}
\IBVSinst{Al. 1-go Maja 29/4, 64500 Szamotuly, Poland
e-mail: macres@pro.onet.pl}
\IBVSinst{Vedecko-kulturne centrum na Orave, 027 42 Podbiel 194, Slovakia
e-mail: vkco@isternet.sk}
\IBVSobj{SS UMi}
\IBVStyp{UGSU}
\IBVSkey{dwarf novae -- photometry}
\begintext
ER UMa stars are a small subgroup of SU UMa-type dwarf novae, which have
extremely short supercycles (the interval between successive superoutbursts)
of 19--50 d (for a review, see Kato et al. 1999). Only four definite members
have been recognized (ER UMa, V1159 Ori, RZ LMi and DI UMa).
Since the shortest known supercycles of ``usual" SU UMa-type dwarf novae
are in the range of 90--130 d (e.g. Table 1 in Nogami et al. 1997),
several objects have been proposed as candidates for the missing link
between ER UMa stars and the usual SU UMa-type dwarf novae: SX LMi
(Nogami et al. 1997), HS Vir (Kato et al. 1998b), NY Ser (Nogami et al. 1998)
and CI UMa (Nogami and Kato 1997). V503 Cyg (Harvey et al. 1995) also
has a supercycle as short as 89 d. However, none of these objects show
perfectly intermediate outburst statistics between ER UMa stars and usual
SU UMa-type dwarf novae. Both HS Vir and NY Ser have short ($\sim$8 d)
outburst recurrence times, while superoutbursts occur more infrequently.
In SX LMi and CI UMa, superoutbursts occur more irregularly and the
frequency of normal outbursts is small. V503 Cyg shows a more regular
supercycle, while the number of normal outbursts (usually two) is
anomalously low compared to ER UMa stars and other SU UMa-type dwarf novae.
The deviation in statistics and regularity of these systems from extremely
regular ER UMa stars should require an anomalous disk viscosity or other
unknown mechanisms (Nogami et al. 1997; Kato et al. 1998b).
The dwarf nova SS UMi was discovered as an optical counterpart of
Einstein IPC source E1551+718 (Mason et al. 1982). The existence of
superhumps during long outburst revealed its SU UMa-type nature
(Chen et al. 1991; Kato et al. 1998a). Richter (1989) studied the
outburst statistics based on 4180 Sonneberg plates and suggested the
possible outburst interval of 30--48 d. This value has been taken over
by Ritter and Kolb (1998) in their sixth edition of ``Catalogue of
Cataclysmic Variables and Low-Mass X-ray Binaries." We continued to
observe SS UMi as a part of VSNET Collaboration
(http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/).
\IBVSfig{8cm}{fig1.ps}{Overall light curve of SS UMi}
Visual observations were performed using 46-cm (G.H.), 40-cm (G.P.),
20-cm (E.M.), 41-cm (M.R.) and 20-cm (P.A.D.) reflectors. All observations
were done using photoelectrically calibrated $V$-magnitude comparison stars.
The typical error of visual estimates were an order of 0.2 mag, which does
not affect the following discussion. Upper limit observations were included
for analysis which reached fainter than 14.0 mag. The total number of
observations was 375 between 1999 February 17 and 2000 June 17, including
other observations reported to VSNET.
The overall light variation is presented in Figure 1. Each filled
square represents single estimates and ``v" sign represents upper limits.
The observations already clearly show the presence of regular outburst
cycle. Since we know that SS UMi belongs to the SU UMa-type category, we can
safely choose outbursts longer than five days as superoutbursts. These
outbursts are marked with vertical bars. The intervals between successive
superoutbursts are in the range of 82--86 d, 84.7 d in average.
All observations are well expressed by this representative supercycle
of 84.7 d. Figure 2 presents a folded light curve by this period.
\IBVSfig{8cm}{fig2.ps}{The 84.7-d supercycle of SS UMi}
We have revealed that SS UMi is an SU UMa-type dwarf nova with one
of the shortest known stable supercycles. Figure 2 suggests the existence
of five normal outbursts between successive superoutbursts, whose interval
corresponds to $\sim$ 11 d. The combination of supercycle length of
84.7 d and the outburst recurrence time of 11 d lies on the natural
extension of SU UMa-type dwarf novae toward ER UMa stars (Warner 1995;
Osaki 1995). Considering that many outbursts recorded by Richter (1989)
were long ones, the period by Richter (1989) may be interpreted to
represent the half supercycle. The present observation has thus first
proven the unique location of SS UMi among ``normal" SU UMa-type dwarf novae
toward ER UMa stars.
The authors are grateful to observers (H. Itoh and J. Ripero) who reported
additional observations of SS UMi to VSNET.
\references
Chen. J.-S., Liu, X.-W., Wei, M.-Z. 1990, A\&A, 242, 397
Harvey, D., Skillman, D. R., Patterson, J., Ringwald, F. A., 1995
PASP, 107, 551
Kato, T., Lipkin, Y., Retter, A., Leibowitz, E., 1998a, IBVS No. 4602
Kato, T., Nogami, D., Masuda, S., Baba, H., 1998b, PASP, 110, 1400
Kato, T., Nogami, D., Baba, H., Masuda, S., Matsumoto, K., Kunjaya, C.,
1999, {\it Disk Instabilities in Close Binary Systems}, p45, eds.
S. Mineshige, J. C. Wheeler (Universal Academy Press, Tokyo)
Mason, K. O., Reichert, G. A., Bowyer, S., Thorstensen, J. R. 1982,
PASP, 94, 521
Nogami, D., Kato, T., 1997, PASJ, 49, 109
Nogami, D., Masuda, S., Kato, T., 1997, PASP, 109, 1114
Nogami, D., Kato, T., Baba, H., Masuda, S., 1998, PASJ, 50, 1L
Osaki, Y., 1995, PASJ, 47, L11
Richter, G. A. 1989, AN, 310, 143
Ritter, H., Kolb, U., 1998, A\&AS, 129, 83
Warner, B. 1995, ApSS, 226, 187
\end{document}
vsnet-adm@kusastro.kyoto-u.ac.jp
Return to Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
VSNET Home Page