Multiwavelength Observations of Gx 339[4 in 1996. I. Daily Light Curves and X-ray and Gamma-ray Spectroscopy

As part of our multiwavelength campaign of GX 339[4 observations in 1996, we present our radio, X-ray, and gamma-ray observations made in July, when the source was in a hard state (\soft X-ray low state). The radio observations were made at the time when there was a possible radio jet. We show that the radio spectrum was Ñat and signiÐcantly variable and that the radio spectral shape and amplitude at this time were not anomalous for this source. Daily light curves from our pointed observation on July 9È23 using the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory (CGRO), from the Burst and Transient Source Experiment (BATSE) on CGRO, and from the All-Sky Monitor on the Rossi X-Ray T iming Explorer (RXT E) also show that there was no signiÐcant change in the X-ray and gamma-ray Ñux or hardness during the time when the possible radio jetÈ like feature was seen. The higher energy portion of our pointed RXT E observation made on July 26 can be equally well Ðtted using simple power law times exponential (PLE) and Sunyaev-Titarchuk (ST) functions. An additional soft component is required, as well as a broad emission feature centered on D6.4 keV. This may be an iron line that is broadened by orbital Doppler motions and/or scattering o† a hot medium. Its equivalent width is D600 eV. Our simplistic continuum Ðtting does not require an extra reÑection component. Both a PLE and an ST model also Ðt our OSSE spectrum on its own. Although the observations are not quite simultaneous, combining the RXT E and CGRO spectra we Ðnd that the PLE model easily Ðts the joint spectrum. However, the ST model drops o† too rapidly with increasing energies to give an acceptable joint Ðt. Subject headings : accretion, accretion disks È binaries : close È black hole physics È stars : individual (GX 339[4) È X-rays : stars