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Black Hole Candidate XTE J1859+226 in the Low/Hard State

ATel #60; J. M. Miller, D. W. Fox, D. Pooley, W. H. G. Lewin (MIT)
on 16 Jul 2000; 20:47 UT
Credential Certification: Derek W. Fox (derekfox@mit.edu)

Subjects: Radio, Optical, X-ray, Request for Observations, Black Hole, Transient

Recent flaring activity of this source in the optical (Casares et al. 2000, IAUC # 7451 ) has motivated a public RXTE TOO observation on 8 July 2000.

XTE J1859+226 is a known X-ray nova that reached 1.4 Crab in the RXTE/ASM in October 1999 (Smith 1999, ATEL #47). During that outburst the source exhibited 150 and 187 Hz quasi-periodic oscillations (Cui et al. 2000, ApJ 535, L123) and radio emission (Pooley & Hjellming, IAUC # 7278 ). The source has been undetected in RXTE/ASM dwells since March 2000.

We find that the PCA spectrum from 8 July 2000 is consistent with hard power-law emission, with photon index alpha=1.54(10) and total 3-25 keV flux of 1.08(20)e-11 ergs cm^-2 (assumed neutral hydrogen column N_H=5.5e21 cm^-2). This spectrum is consistent with the canonical Low/Hard spectral state of black hole X-ray binary systems.

Observers may contact the authors (jmm@space.mit.edu) for possible coordination with their ongoing multi-wavelength campaign on this source.