[vsnet-alert 2690] U Sco eclipse ephemeris

[Taichi Kato <tkato>]

U Sco eclipse ephemeris

   The detection of the U Sco outburst by P. Schmeer (vsnet-alert 2688,
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-alert/msg02688.html)
is one of the most wanted news in the recent decade!  Congratulations!!

   After the latest outburst in 1987 (whose peak may have been missed),
U Sco became recognized as an eclipsing binary (only known one in recurrent
novae).  The present outburst provides an unique opprortunity in spatially
resolving the outbursting recurrent (and very fast, helium-rich, unique)
nova.  The predicted eclipse times after Schaefer and Ringwald's (ApJ 447, L45)
revised ephemeris:

   Min.HJD = 2447717.6061 + 1.2305631 E
                    +/-32       +/-30

  YYMMDD hh:mm:ss (UT)
 ------------------
  990225 01:19:55
  990226 06:51:45
  990227 12:23:35
  990228 17:55:25
  990301 23:27:15
  990303 04:59:05
  990304 10:30:56
  990305 16:02:46
  990306 21:34:36
  990308 03:06:26
  990309 08:38:16
  990310 14:10:06

   Time-resolved photometry and spectroscopy around all phases, esp. around
predicted eclipses, are most urgently requested.  The latest eclipse should
have occurred four hours ago; didn't anyone observe around this time?

   Considering the cycle count amgibuity (though most seems to have been
rejected by Schaefer and Ringwald), observers at other longitudes may have
a chance to observe eclipses.  Please concentrate on this particular object.

   Observers may interested to know significant short-term variability was
observed during the 1987 outburst.  We indeed (with S. Fujino) observerd by
photography, but modern CCD technology will certainly give the answer.

Regards,
Taichi Kato

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