[vsnet-alert 4776] The UMa transient's got the shakes

[Joe Patterson <jop@astro.columbia.edu>]

                           XTEJ1118+480

     More details on the optical coverage of this remarkable X-ray/optical
transient are given on the CBA website at www.astro.bio2.edu/cba.  During     
April 30-May 3 Dave Skillman at CBA-Maryland (26" f/2.9 telescope, AP-7 
camera unfiltered) carried out high-speed (1 s integration + 2.1 s readout) 
observations.  The periodogram showed a powerful quasiperiodic signal 
at 9.9 seconds.  The error in the peak is ~0.2 s, with excess power 
between 9 and 11 s.  The signal amplitude is very high, sometimes reaching
0.20 mag.  Because the star's 10 s clock is very sloppy - losing track of 
phase in just a few cycles - the variations are primarily manifest as a 
huge scatter in rapidly sampled data.  This is an impressively noisy star!

     Measurement with photomultiplier tubes and trailed CCD images are 
also recommended.  What will happen to this amazing signal as the star     
fades?  

     We're also continuing to follow the 4.1 hour variation with slower
photometry.  We'd love to collaborate with any observers out there
interested in time-series photometry of this star on any time-scale.    


The CBA "UMa transient" cabal, so far

Joe Patterson - CBA-New York     jop@astro.columbia.edu
Bob Fried - Braeside Observatory
Dave Harvey - CBA-Tucson
Lew Cook - CBA-California
Gianluca Masi - CBA-Italy
Jonathan Kemp - CBA-Oracle
James Hannon - CBA-Connecticut
Denis Buczynski - Condor Brow Observatory
Tonny Vanmunster - CBA-Belgium
Lisa Pidgley, Pierre Maxted, Sofia Araujo-Betancor - Southampton Univ.
Rudolf Novak - Nicolas Copernicus Observatory (Brno)
Dave Skillman - CBA-Maryland
Brian Martin - CBA-Alberta

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