SPECTRAL VARIATIONS IN THE LOW-MASS X-RAY BIN ARY 4U-0614+09

We report the X-ray spectra of a binary 4U 0614 + 09 observed with EXO SAT on five different occasions in 1984 and 1986. In four observations in 1984, the source intensity was 'low'' compared to its intensity in the 1986 observation. The source was steady on timescales of 10-1000 s in each of the 1984 observations but highly variable during the 1986 variations. The best-fit spectral models for the continuum are a blac kbody spectrum plus an emission from a Comptonized region. In addition , a component due to reflection from a cold disk around the source was needed as an absorbtion edge due to cold or ionized iron was seen nea r 7 keV with good significance in most of the spectra, particularly in the ''low'' state. The relation of the hardness ratios with intensity follow the behavior seen in the ''Atoll'' sources. We have studied th e behavior of the hardness ratios with the variations in the parameter s of the best-fit spectral models. Most of the variability is associat ed with the blackbody component thought to arise from the boundary lay er on the surface of the neutron star. During the 'high'' state in 198 6, the blackbody temperature is higher, its size smaller, and its cont ribution significantly greater than in the ''low'' state. The other no table difference between the two states is the lower opacity in the Co mptonized region, and a significantly higher absorption in the ''high' ' state. A weak line emission (equivalent width = 10-40 eV) is detecte d during the ''high'' state. The line energy lies between 6 and 7 keV which implies its origin from ionized ion.