ar X iv : a st ro - p h / 98 12 16 3 v 1 8 D ec 1 99 8 OBSERVATIONS OF GX 339 – 4 IN 1996

GX 339–4 is an unusual black hole candidate in that it is a persistent source, being detected by X-ray telescopes most of the time, but it also has nova-like flaring states. In 1996 we performed radio, optical, X-ray, and gamma-ray observations of GX 339–4 when it was in a hard state (= soft X-ray low state). Here we present a brief summary of some of the results. At this time, neither the ASM on the Rossi X-Ray Timing Explorer (RXTE) nor BATSE on the Compton Gamma-Ray Observatory (CGRO) detected the source. We had hoped that the lack of detectable high-energy emission would make it possible to observe the companion star for the first time. However, we found that the optical emission was still dominated by the accretion disk with V ≈ 17 mag. This is typical for the source in the low state, V ≈ 15.4 − 20.2 (Tanaka & Lewin 1995). The dominant emission line in our spectra is Hα. Its equivalent width (EW) of ∼ 6.5 ˚ A is similar to the lines seen in previous GX 339–4 observations (Grindlay 1979, Cowley, Crampton, & Hutchings 1987). However, this is small compared to other black hole X-ray novae (BHXRN); for example, the Hα line in Nova Oph 1977 had EW = 85Å during our observing run (Filippenko et al. 1997). For the first time in GX 339–4 we were able to resolve the Hα line and show it has a double peaked profile. The peak separation implies a ∆v = 370 ± 40 km s −1 .