(cba:news) [vsnet-alert 4690] The X-ray transient in UMa (fwd)

Jonathan Kemp jk at cbastro.org
Fri Apr 28 16:05:45 EDT 2000

---------- Forwarded message ----------
Date: Fri, 28 Apr 2000 15:58:20 -0400 (EDT)
From: Joe Patterson <jop at astro.columbia.edu>
To: vsnet-alert at kusastro.kyoto-u.ac.jp
Subject: (cba:news) [vsnet-alert 4690] The X-ray transient in UMa


27 nights of photometric observation with the globally distributed
telescopes of the Center for Backyard Astrophysics yield a precise period
of 0.17082(11) d and full amplitude 0.052 mag in the optical counterpart
of the X-ray transient.  Variability on other (shorter and longer) 
timescales is largely absent, except at very short periods where the 
star's behavior is quite amazing.  Large-amplitude (>0.3 mag) flickering 
is present on timescales <10 seconds, in all passbands (U through I).  
Observations with very high time resolution are needed to define this 
remarkable phenomenon.  It's a particularly fine project for 
photomultiplier tubes (or for telescopes without clock drives!).  In 
fact, it would be interesting to know if VISUAL observers can detect this 
flickering.  More details are available at www.cbastro.org.

We are extremely interested in hearing from others who have observed, or
are interested in observing, this wonderful star!

Observations over the next week are particularly timely, since various
spacecraft (HST, RXTE) will observe the star repeatedly during the week.

The CBA "UMa transient" cabal

Joe Patterson - CBA-New York     jop at 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.

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