Multiwavelength observations of XTE J1859+226
C. A. Haswell, S. Chaty (Open University), W. Cui (NASA/GSFC/U. MD.), J. V. Casares (IAC), and R. I. Hynes (Southampton University)
On March 2 06:00 UT the transient source XTE J1859+226 had faded considerably to R=18.0 in the optical (IAC) and to a flux of about 13 mCrab (RXTE ASM). However, it clearly remains active in the X-rays. From extrapolating the last spectrum obtained with HST on 2000, February 8th we predict the following approximate magnitude and colours: V~18.4, U-B=-0.5, B-V = V-R = R-I = +0.4.

A final simultaneous HST/RXTE visit to this source (most likely a black hole) is scheduled for 2000, March 5th between 06:10 and 13:41 UT. Time details are given below.

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.

The target is now an end-of-night object, observable for about 2 hours before twilight. Details of the target are given in IAUC # 7274 , IAUC # 7276 , IAUC # 7278 , IAUC # 7279 , IAUC # 7282 , IAUC # 7284 , IAUC # 7291 , ATEL #47 and ATEL #50. The coordinates are R.A. = 18h58m41s.51, Decl. = +22o39'30".2 (J2000.0). Garnavich et al. 1999 (IAUC 7276 ) give a finder chart (see link below). ***** For a best multiwavelength coverage purpose, the HST and detailed XTE schedule of the science observations is given below: ### HST ### HST observations start: Mar 5 2000 06:10:16 UT end: Mar 5 2000 13:41:12 UT. ### XTE ### 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.
radio,millimeter,sub-millimeter,far-infra-red,infra-red,optical,ultra-violet,x-ray,gamma ray,binary,black hole,neutron star,star,transient,request for observations,a comment