[vsnet-alert 4332] Multiwavelength Observations of RXTE J1859+226 on March 5 UT.

[Carole A Haswell <C.A.Haswell@open.ac.uk>]

A final HST/RXTE visit to this source (most likely an
accretion disk emptying into a black hole) is scheduled 
for March 5:
HST observations start:  Mar 5 2000 06:10:16 UT
                   end:  Mar 5 2000 13:41:12 UT

RXTE observations on source intervals:
                                     Mar 5 2000 07:23:00 to 08:21:00 UT
                                     Mar 5 2000 08:59:00 to 09:57:00 UT
                                     Mar 5 2000 10:34:00 to 11:18:00 UT.

Coordinated multiwavelength observations (simultaneous, 
near-simultaneous, and following the evolution over days/weeks/months) 
would be extremely helpful. Simultaneous or near simultaneous
red and infrared photometry or spectrophotometry (where we have no 
satellite coverage); and/or photometry with time-resolution greater that
about 10s (where the signal to noise ratio justifies this) is particularly 
solicited. Observers contributing data will become Co-Authors. 

Details of the target are given in IAU circs 7274, 7276, 7279, 7284.
The coordinates are R.A. = 18h58m41s.51, Decl. = +22o39'30".2 (J2000.0).
Garnavich et al. (IAUC 7276) give a finder chart at 
http://cfa-www.harvard.edu/~peterg/gosox/j1859.jpg.
On March 2 06:00 UT RXTE J1859+226 had faded considerably to
R=18.0 (Casares, private communication) and RXTE ASM flux 
of about 13 mCrab, but clearly remains 
X-ray active. The target is now an end-of-night object, observable 
for about 2 hours before twilight.

From extrapolating the 8 Feb HST spectrum we
We predict the following approximate magnitude and colours:
V~18.4, U-B=-0.5, B-V = V-R = R-I = +0.4.


For further information please contact Rob Hynes (rih@astro.soton.ac.uk),
Sylvain Chaty (S.Chaty@open.ac.uk), 
Carole Haswell (c.a.haswell@open.ac.uk),
or Wei Cui <cui@space.mit.edu>.

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