[vsnet-alert 4530] BC UMa bright outburst

[Taichi Kato <tkato>]

BC UMa bright outburst

    Following observations have been reported.  BC UMa is one of famous
large-amplitude SU UMa-type dwarf novae with very long outburst intervals.
The latest outburst (according to my record) of BC UMa was observed on
1994 April 28, which was detected by M. Iida (VSOLJ) at mv=12.5, who
subsequently detected first-ever superhumps in this star using a 16-cm
reflector and a CCD.  The observation first established the SU UMa-type
nature of BC UMa.  The finding was confirmed by CCD photometry at Ouda
Station (Kyoto University) by Kunjaya et al.  The superhump period by
Iida was 0.0619 d.  The 1994 outburst lasted for at least 11 days,
and was one of the faintest superoutburst of this star.

    BC UMa is one of famous dwarf novae which show both bright and faint
superoutbursts (other known examples include SW UMa and WX Cet).  The
present outburst is almost certainly one of "bright superoutburst" after
the six years of dormancy.  The present brightness level was only reached
on a few occasions, including the 1990 September outburst (mv=10.9, Dyck,
IAUC 5089, unfavaorably located) and the 1982 May outburst (mv=10.7 according
to the VSOLJ record).  The present outburst thus provides the first-ever
favorable opportunity to clarify the nature of a bright superoutburst.
We are very looking forward to hearing successful time-series CCD photometry
reports from worldwide, and Please post timely to vsnet-alert confirmatory
observations, new findings, the progess of the outburst and observations.

  YYYYMMDD(UT)   mag  observer
  20000324.823  <140  (E. Muyllaert)
  20000324.876  <153  (G. Poyner)
  20000325.507  <144  (T. Watanabe)
  20000325.860  <153  (T. Kinnunen)
  20000325.906  <158  (G. Poyner)
  20000326.017  <140  (H. McGee)
  20000326.612  <134  (H. Maehara)
  20000326.850  <153  (T. Kinnunen)
  20000326.869  <140  (E. Muyllaert)
  20000327.256  <153  (G. Hanson)
  20000327.812  <136  (M. Westlund)
  20000327.919  <153  (T. Kinnunen)
  20000328.800  <137  (P. Schmeer)
  20000328.869  <153  (T. Kinnunen)
  20000329.692  <136  (H. Maehara)
  20000329.833  <136  (M. Westlund)
  20000329.899  <153  (T. Kinnunen)
  20000330.790  <153  (T. Kinnunen)
  20000331.799   121  (P. Schmeer)
  20000331.835   113  (T. Kinnunen)
  20000331.851   119  (P. Schmeer)
  20000401.169   111  (E. Muyllaert)

Regards,
Taichi Kato and Makoto Uemura
On behalf of the VSNET Collaboration team

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