IXAE observations of the X-ray pulsar XTE J1946+274

We report results from two observations of the transient binary X-ragi puls ar XTE J1946+274 with the Indian X-ray Astronomy Experiment (IXAE) made in September 18-30 1999 and June 28-July 7 2000. The pulsar has a similar to 8 0 days orbital period during which the, X-ray intensity varies almost sinus oidally between intensity levels of 5 and 50 mCrab. The mid-time of the two observations with the IXAE are separated by an orbital phase of 0.56 and w ere in the decaying and rising parts of its orbital modulation, respectivel y. During both the observations, strong pulsations with 15.8 s period are d etected in the 2-6 and 6-18 keV energy bands of IXAE. The pulse profiles in both the observations are double peaked and identical with a similar pulse fractions of similar to 30% in the two energy bands. The pulse periods and its local derivatives are obtained from the IXAE observations. The known p ulse period history shows small deviations from an otherwise nearly constan t spin-up trend of the pulsar since its discovery. If the measured local pe riod derivatives are a sum of a nearly constant spin-up of the pulsar and e ffect of its: orbital motion, it suggests that the orbit of this Be X-ray b inary is eccentric. The RXTE-ASM light curve shows a continuous detection o f 10 orbital modulation of the source since its discovery.