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[vsnet-campaign-news 156] V359 Cen: superoutburst of a newly established SU UMa-type dwarf nova!
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V359 Cen: superoutburst of a new SU UMa-type dwarf nova
-- the nature of the possible nova in 1939 finally revealed!
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V359 Cen was discovered as a possible nova (1939) by A. Opolski on
Franklin-Adams plates. The second historically known outburst was
discovered by Rod Stubbings (Australia) on 1999 July 13 (vsnet-alert 3216).
Subsequent observation during this outburst showed that the object
is likely a dwarf nova, pending future detailed observations.
On 2002 May 28, Rod Stubbings reports that V359 Cen is again
undergoing an outburst (vsnet-alert 7356) [The object was also seen in
outburst in 2001 April (vsnet-alert 4849), but no detailed observation
was performed].
YYYYMMDD(UT) mag observer
20020502.421 <146 (Rod Stubbings)
20020503.428 <144 (Rod Stubbings)
20020504.415 <150 (Rod Stubbings)
20020506.403 <148 (Rod Stubbings)
20020506.449 <140 (Peter Nelson)
20020507.390 <140 (Rod Stubbings)
20020508.378 <148 (Rod Stubbings)
20020509.515 <150 (Rod Stubbings)
20020511.558 <148 (Rod Stubbings)
20020513.396 <150 (Rod Stubbings)
20020514.419 <148 (Rod Stubbings)
20020515.625 <140 (Rod Stubbings)
20020516.387 <148 (Rod Stubbings)
20020519.685 <138 (Rod Stubbings)
20020524.387 <138 (Rod Stubbings)
20020525.399 <138 (Rod Stubbings)
20020527.410 <138 (Rod Stubbings)
20020528.362 138 (Rod Stubbings)
20020528.380 138 (Rod Stubbings)
20020528.406 138 (Rod Stubbings)
Upon this information, Roland Santallo (Southern Stars Observatory,
Tahiti) conducted CCD time-series observations, and successfully detected
genuine superhumps. The best period determined by the VSNET Collaboration
team is 0.08136(8) d (=117 min). This observation has finally established
the true classification of this once suspected nova.
Up to now, only superoutbursts have been detected with a mean interval
of ~1 year. Although this might be resulted from the difficulty in
detecting fainter normal outbursts, the apparent lack of normal outbursts
may be a result of a low mass-transfer rate. This possibility may explain
the long persistence of the signal following the superoutburst (now
unambiguously identified!) in 1999 (Woudt et al. (2001) MNRAS 328, 159),
which had a period close to what it presently observed. Only a few systems
(WZ Sge being the best example) are known to show such a long persistence
of the "late superhump" signal.
Systems with similar outbursts and orbital parameters include EF Peg
and V725 Aql, both of which show unusually infrequent outbursts for their
superhump period. [References: EF Peg: Kato (2002) PASJ 54, 87;
V725 Aql: Uemura et al. (2001) PASJ 53, 539]. Both stars have (at least
on one occasion) shown virtually zero period changes in contrast to
the "textbook" negative period derivatives in ordinally SU UMa-type
dwarf novae.
Further observations of superhumps in V359 Cen throughout the current
superoutburst are therefore urgently requested to determine the period
derivative; accurate measurement of times of superhump maxima (at least
once per night) is a very recommended protocol. V359 Cen may show
a rebrightening, as was observed in V725 Aql. Nightly monitoring
following the present superoutburst is also highly encouraged.
Further information can be seen at:
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/DNe/v359cen.html
Regards,
Taichi Kato
VSNET Collaboration team
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VSNET (Variable Star Network) is an international variable star observing
network, covering various areas of novae, supernovae, cataclysmic variables
(CVs), X-ray transients, and other classical eruptive, pulsating, and
eclipsing variables. VSNET is one of invited contributing organizations
to the SkyPub AstroAlert system.
VSNET Home Page: http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/
CCD observations of such targets are a relatively easy task for a 20-40cm
telescope; simply take as many CCD frames (with exposure times 10-30 sec)
as possible, spanning several hours per night. The only requirements are
the weather and your patience! If you need more help on the observing
technique, please feel free to ask on the vsnet-campaign list.
We would sincerely appreciate volunteers who would join the VSNET
Collaboration team to study the wonders of these exotic variable stars.
To join the VSNET campaign collaborative list, send an e-mail to
vsnet-adm@kusastro.kyoto-u.ac.jp (VSNET administrator)
with a line "SUBSCRIBE vsnet-campaign." or your comment to join the
collaboration team.
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