[vsnet-alert 917] (fwd) V651 Mon: urgent request for observations

[Taichi Kato <tkato>]

Forwarded message from Rafael Costero <costero@astroscu.unam.mx>

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I am somewhat worried about the lack of recent visual or CCD observations 
of V651 Mon. This central star of the planetary nebula NGC 2346 is now 
exiting from behind the (hypothetical) dense, dust cloud that practically 
"erased" it from the sky. 

As you surely know, supposedly tonight or tomorrow the bright component of 
the spectroscopic binary will, in its orbital motion, appear from behind 
the obscuring cloud, just to re-enter back a few days (?) later. These 
appearances should now repeat about every 16 days (the orbital period of 
the binary), predictively in ever brighter and longer episodes. It is of 
great importance to measure both the timing and intensity of such 
"brightennings" (now up to magnitudes brighter than 12v) and of the 
progressively brighter light-curve minima, in order to better know the 
physical characteristics of the cloud. (Size, density gradient, etc.) 

I hence urge those VSNET members that have been following this second (known) 
occultation episode series (like Gary Poyner, Watanabe San, the Ouda team, 
Robert Modic, etc.) to keep on with their extremely valuable observations of 
this interesting object. There are only 5 such observations during the last 
35 days or so (vsnet 1019, Circular 1997.04; vsnet-obs 5799) and NONE since 
May 10! All of us interested in these phenomena will highly appreciate the 
help of those of you who contributed with fundamental data during the onset 
of the current episode (and certainly that of all newcomers).

I gratefully acknowledge your enthusiastic interest in this object (e.g. 
vsnet-alert 848) and kind help.

Rafael Costero
Instituto de Astronomia, UNAM; Mexico
costero@astroscu.unam.mx

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Summary of visual and CCD observations:

  YYMMDD(UT)   mag  code
  970227.001  <134  POY
  970227.440  <138  Ths
  970227.548  14.26V  Oud
  970227.800  <131  CSK
  970228.460  14.04V  Oud
  970228.906  <145  POY
  970301.310   141  SNO
  970301.433  <135  Ths
  970301.537  14.06V  Oud
  970302.885  <139  POY
  970305.466  14.26V  Oud
  970306.848  <145  POY
  970308.488  14.16V  Oud
  970310.849  <139  POY
  970311.448  13.85V  Oud
  970312.828   146  POY
  970319.824   140: POY
  970324.492  <134  Wnt
  970324.858  <139  POY
  970326.874  <145  POY
  970328.417  14.01V  Oud
  970329.865   146: POY
  970330.421  13.26V  Oud
  970330.533   131: Wnt
  970331.430  12.92V  Oud
  970331.839   128  POY
  970331.910   129: AFO
  970401.421  12.24V  Oud
  970402.169   118  MRV      * brightness spike emerged
  970410.858  <139  POY
  970413.424  14.00V  Oud
  970414.438  13.96V  Oud
  970415.113  <142  MRV
  970415.875  <139  POY
                             * unfortunately no observations
                               (Apr 2 + 16 d)
  970426.469   131  Wnt
  970429.465   131  Wnt
  970505.482   119  Wnt      * brightness spike (Apr 2 + 16 d x 2)
  970507.103   121  MRV
  970510.455   133  Wnt

  ???                        * spike expected around now!

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