[vsnet-alert 9101] GSC3656.1328 up to now, and on the microlensing interpertation

[Taichi Kato]

  GSC3656.1328 up to now:

  By assuming the microlensing interpretation (ATEL #931, apparently
not appearing in VSNET lists),

===
ATEL #931							     ATEL #931

Title:		The bright new variable in Cassiopeia - a microlensing event?
		
Author:	M. Mikolajewski, T. Tomov, A. Niedzielski, K. Czart, C. Galan
		- Torun Center for Astronomy, Nicolaus Copernicus University, 87-100
		Torun, Poland
Queries:	aniedzi at astri.uni.torun.pl
Posted:	3 Nov 2006;  20:56  UT
Subjects:	Optical, Microlensing Events, Variables, Stars

We report BV photometry and optical spectroscopic observations of a bright
new variable in Cassiopeia, identified as GSC 3656-1328 (CBET # 711,
# 712).   According to SIMBAD database GSC 3656-1328 is a 11.4 star in
V with B-V of about 0.2.      Our spectra in the region 3700-7300AA and
at a resolution of 4A were obtained with   the 60/90cm Schmidt-Cassegrain
telescope of Torun Observatory between 2006   November 02.790 UT and November
03.713 UT. They  show a typical A0V-A1V   star without remarkable spectral
variations or line shifts. The Balmer   absorptions show an average radial
velocity of -45 +/-15 km/s. The brightness   estimate: V=10.15 and B=10.35
was obtained with the  60cm Cassagrain   telescope of Torun Observatory
on 2006 November 02.765 UT.      The SIMBAD data show that before the event
GSC 3656-1328 was  a slightly   reddened A0V-A1V star at a distance of
about 1 kps. The only observed change   was a sudden rapid increase and
then a decrease of the brightness with an amplitude   about 4 mag without
any spectral changes. It is difficult to associate such   an observed phenomenon
with any type of variable stars. A possible   explanation of the GSC 3656-1328
behavior could be a gravitational   microlensing event. If that is the
case, this would be the closest   microlensing event ever observed.  
===

   the expected peak may have been somewhere before Tago's observation
on Oct. 31.  By fitting the light curve weighing on the fading
branch, the peak should have been somewhere between Tago's observation
and Oct. 31 7h UT (may have even reached a naked-eye magnitude).
An earlier peak (though the expected symmetry of the light curve would
favor an earlier one) is difficult to reproduce a high amplification at
the time of Tago's observation.
Could there be photographs or CCD images around these epochs?
Any material would be extremely helpful, and needs to be preserved
before they might be lost.

  YYYYMMDD(UT)   mag  observer
  20061021.517  <114C  (Kazuyoshi Kanatsu)
  20061025.538  107C  (A. Tago)
  20061027.408  105C  (A. Tago)
  20061030.410   88C  (A. Tago)
  20061030.522   89C  (Kazuyoshi Kanatsu)
  20061031.469   75C  (A. Tago)
  20061031.842   77p  (Keith Geary)
  20061031.890    85  (Maciej Reszelski)
  20061031.910    86  (Reinder J. Bouma)
  20061031.926    86  (John Toone)
  20061101.033    86  (Bjorn H. Granslo)
  20061101.176    87  (Gary Poyner)
  20061101.378    92  (Mike Linnolt)
  20061101.387    93  (Susumu Takahashi)
  20061101.496    93  (Hirohisa Sato)
  20061101.522  9.28Rc  (Seiichiro Kiyota)
  20061101.524  9.27Ic  (Seiichiro Kiyota)
  20061101.526  9.41V  (Seiichiro Kiyota)
  20061101.606    93  (Yutaka Maeda)
  20061101.708    94  (Hans-Goran Lindberg)
  20061101.722    95  (Wolfgang Kriebel)
  20061101.735    93  (Bjorn H. Granslo)
  20061101.758    95  (Reinder J. Bouma)
  20061101.767    95  (Stanislaw Swierczynski)
  20061101.774    93  (Gary Poyner)
  20061101.780    95  (Georg Comello)
  20061101.907    97  (Erwin van Ballegoij)
  20061101.983    97  (Stanislaw Swierczynski)
  20061102.457    99  (Susumu Takahashi)
  20061102.526  10.01V  (Seiichiro Kiyota)
  20061102.530  10.02Rc  (Seiichiro Kiyota)
  20061102.531  9.99Ic  (Seiichiro Kiyota)
  20061102.688    95  (Hans-Goran Lindberg)
  20061102.773   102  (Gary Poyner)
  20061102.819   103  (Erwin van Ballegoij)
  20061102.862    97  (Georg Comello)
  20061102.952   103  (Laurent Bichon)
  20061102.988   102  (Stanislaw Swierczynski)
  20061103.694  10.42Ic  (Hiroyuki Maehara)
  20061103.695  10.44Rc  (Hiroyuki Maehara)
  20061103.697  10.51V  (Hiroyuki Maehara)
  20061103.699  10.64B  (Hiroyuki Maehara)
  20061103.721   103  (Wolfgang Kriebel)
  20061103.753   104  (Gary Poyner)
  20061103.753   104  (Eddy Muyllaert)
  20061103.769   105  (Reinder J. Bouma)
  20061103.817  10.57V  (Roger Pickard)
  20061103.823  10.44R  (Roger Pickard)
  20061103.978   105  (Stanislaw Swierczynski)
  20061104.412  10.76V  (Kazuhiro Nakajima)
  20061104.417  10.95B  (Kazuhiro Nakajima)
  20061104.421  10.69Rc  (Kazuhiro Nakajima)
  20061104.690  10.65Ic  (Hiroyuki Maehara)
  20061104.691  10.68Rc  (Hiroyuki Maehara)
  20061104.692  10.71V  (Hiroyuki Maehara)
  20061104.694  10.89B  (Hiroyuki Maehara)