[vsnet-alert 1690] Re: XX Cam

[Taichi Kato <tkato>]

  Compiled from recent reports to VSNET:

  YYMMDD(UT)   mag  observer
  980124.808    73  (J. Toone)
  980125.008    76  (M. Reszelski)
  980125.933    76  (M. Reszelski)
  980126.719    73  (M. Moeller)
  980127.574    74  (M. Nakatani)
  980129.796    76  (M. Reszelski)
  980131.714    73  (M. Moeller)
  980131.922    76  (M. Reszelski)
  980131.940    74  (Z. A. Nagy)
  980201.831    76  (M. Reszelski)
  980201.899    76  (L. Kiss)
  980202.556    75  (M. Nakatani)
  980205.799    73  (R. Fidrich)
  980207.799    73  (R. Fidrich)
  980211.517    76  (M. Nakatani)
  980218.899    74  (R. Fidrich)
  980219.800    74  (R. Fidrich)
  980221.800    73  (R. Fidrich)
  980223.800    75  (L. Kiss)
  980228.890    76  (J. Toone)
  980301.800    73  (L. Kiss)
  980302.791    73  (M. Moeller)
  980304.542    75  (M. Nakatani)
  980309.781    77  (M. Reszelski)
  980311.785    75  (M. Reszelski)
  980314.876    77  (M. Reszelski)
  980315.900    75  (L. Kiss)
  980323.800    74  (L. Kiss)
  980330.847    77  (J. Toone)
  980403.451    74  (M. Nakatani)
  980415.866    78  (J. Toone)

  Although the reality of the fade needs more confirmation, here is some
more information on XX Cam:

  This object was designated as HD 25878 = BD+52.771.  Later Gaposhkin
reported the existence of narrow hydrogen emission lines.   Further
Bidelman (1948) pointed out the remarkable similarity between the spectea of
this star and R CrB (very weak hydrogen lines and the existence of carbon
absorption), calling it a "hot carbon star".  After Bidelman's suggestion,
Chang Yuin checked 1170 Harvard plates since 1898, and actually found one
minimum resembling R CrB-type fading:

    JD       pg
  2429566   8.60     29613   9.70      29632  10.18
      586   8.60       614   9.70        633  10.30
      592   8.84       621  10.18        634  10.30
      596   8.84       622  10.18        636  10.18
      603   9.22       622  10.18        639  10.06
      605   9.22       625   9.94        646   9.82
      607   9.58       625  10.18        646   9.82
      607   9.58       625  10.30        649   9.82
      608   9.58       626  10.06        658   9.34
      613   9.58       630  10.30        659   9.58
      613   9.70       632  10.30        661   9.22
      613   9.70       632  10.42        678   8.72

  The star, thus named as XX Cam, has been intensively monitored by
visual observers, but no further fading has been reported.  The present
episode, if confirmed, would provide an unprecedented opportunity in
determining the real nature of the XX Cam fade -- true R CrB star or
other phenomenon.  Spectroscopic observations, multi-color photometry
and polarimetry would be very important.

Regards,
Taichi Kato

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