Study of Hard X-ray Sources with a Large Area Xenon Detector Telescope ------------------------------

• Several balloon flights have been made in the past with this telescope to study the hard X-ray (20-100 keV) emission from X- ray binaries and Active Galactic Nuclei. To improve the detection sensitivity at low energies, a much larger (414,000 Cu.M) indigenously fabricated balloon was used for a balloon flight. A balloon flight was carried out on 21/22 March, 1995 to study the Galactic X-ray source GX 1+4. Using an on-board programmable source tracking system, the source was observed for a long duration (~160 minutes).

  (P.C. Agrawal, B. Paul, A.R. Rao, M.R. Shah D.K. Dedhia, R.K. Manchanda, K. Mukherjee, P.Shah).

• The Galactic center X-ray pulsar GX 1+4 shows a steady spin down after its low state in 1983-84 period. During the present high luminosity state the X-ray luminosity is about 8 1037 erg s- 1. Periodicity in the source was detected with high accuracy and it was concluded that the source is in a transition state from the spin-down episode to spin-up episode. A significant difference in the hard X-ray pulse profile has been discovered.

  (B. Paul, P.C. Agrawal, A.R. Rao and R.K. Manchanda)