[vsnet-alert 7614] UV Gem: long-period SU UMa-type dwarf nova (near the stability border?)

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

UV Gem: long-period SU UMa-type dwarf nova (near the stability border?)

Dear Colleagues,

   We have finished analyzing the Kyoto and Okayama U. of Sci. data taken
on Jan. 6.  The data clearly show the growing stage of the superhumps,
which smoothly evolved into the Nyrola observatory observation.
We have just received a new set of data from Jochen Pietz on Jan. 7.
Pietz's data clearly show a further growth of the superhump amplitude!

   From the initial part (Jan. 6) of the data, we obtained a period
of 0.0945(8) d.  A combined set with the Jan. 7 yielded a substantially
longer period of 0.0959 d.  This finding again suggests the early rapid
evolution of the superhump period, possibly continuous from the period
close to the orbital period (see vsnet-alert 7613 for NSV 10934, and
Kato 1997, PASJ 49, 583 for T Leo).

   These observations have apparently established the long-period nature
of UV Gem (the fifth longest superhump period ever recorded for SU UMa
stars).  The object is likely located near the lower edge of the period
gap.  This long period (through a possibly large mass-ratio close to
the stablity condition for the tidal instabilities) may be responsible
for the occasional absence of superhumps even in long outbursts.
If this possibility is confirmed, UV Gem may be the second object
(second to TU Men) which has intermediate properties between SU UMa-type
and SS Cyg-type dwarf novae!

   The Kyoto team and contributing VSNET Collaboration members have
successfully obtained Jan. 7 data, which are being analyzed.  We will be
able to report a refined result when we finish analyzing these observations.
Further observations are strongly encouraged!

Regards,
Taichi Kato
VSNET Collaboration team

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