[vsnet-alert 9545] WZ Sge-type HS2331+3905 bright outburst: early evolution

[Taichi Kato]

   WZ Sge-type HS2331+3905 bright outburst up to now.
Now reached somewhere close to WZ Sge itself!
(cf. http://www.kusastro.kyoto-u.ac.jp/vsnet/DNe/wzsge01.html
for more on WZ Sge in 2001 and you will see what to observe
this time!)

   The absence of orbital humps and strong He II emission lines during
the early rising stage strongly suggests that the outburst was not
triggered by a mass-transfer burst phenomenon, and the outburst looks
like to be "outside-in" type (rapid rise, later appearance of He II
lines).  Both of these findings (still under investigation, though)
support the disk-instability model for a WZ Sge-type outburst.
The "outside-in"-type outburst (if confirmed) suggests that the
instability did not occur close to the white dwarf (as often supposed
in magnetically truncated models).  The lack of earlu IP-type signature
(in spectroscopy) is also in line with this interpretation.

  YYYYMMDD(UT)   mag  observer
  20070831.201  164C  (Gobet Franck)
  20070831.205  16.07C  (Gary Poyner)
  20070902.685  16.03V  (Hiroyuki Maehara)
  20070903.192  16.24C  (Gary Poyner)
  20070903.194  163C  (Gobet Franck)
  20070903.869  <142  (Patrick Schmeer)
  20070903.869  <142  (Patrick Schmeer)
  20070903.893  <146  (Eddy Muyllaert)
  20070904.775  14.59V  (Hiroyuki Maehara)
  20070904.798  144V  (Higashi-Hiroshima Observatory (Hiroshima Univ.))
  20070904.822  141V  (Higashi-Hiroshima Observatory (Hiroshima Univ.))
  20070904.842  13.81C  (Jeremy Shears)
  20070904.843   139  (Eddy Muyllaert)
  20070904.864   132  (Eddy Muyllaert)
  20070904.867   128  (Patrick Schmeer)
  20070904.867   128  (Patrick Schmeer)
  20070904.894   127  (Eddy Muyllaert)
  20070904.918   124  (Eddy Muyllaert)
  20070904.923  12.261CV  (Diego Rodriguez)
  20070904.924  12.212CV  (Diego Rodriguez)
  20070904.926  12.209CV  (Diego Rodriguez)
  20070904.927  12.190CV  (Diego Rodriguez)
  20070904.928  12.156CV  (Diego Rodriguez)
  20070904.928  12.193CV  (Diego Rodriguez)
  20070904.929  12.137CV  (Diego Rodriguez)
  20070904.943   120  (Eddy Muyllaert)
  20070904.992   115  (Bjorn H. Granslo)
  20070905.001   112  (Hans-Goran Lindberg)
  20070905.019   111  (Hans-Goran Lindberg)
  20070905.032   112  (Bjorn H. Granslo)
  20070905.034   110  (Hans-Goran Lindberg)
  20070905.098   104  (J. Bortle)
  20070905.103  112V  (Bob Koff)
  20070905.164  10.408V  (Martin Nicholson)
  20070905.165  10.492B  (Martin Nicholson)
  20070905.352  9.604V  (Martin Nicholson)
  20070905.353  9.579B  (Martin Nicholson)
  20070905.478   92V  (Bob Koff)
  20070905.494    88  (Yutaka Maeda)
  20070905.569    89  (Yutaka Maeda)
  20070905.664    87  (Yutaka Maeda)
  20070905.903    87  (Eddy Muyllaert)
  20070905.927    82  (Eddy Muyllaert)