P. K. Kunte

High energy X-ray timing and spectral observations of SCO X-1, CYG X-1, GX 5-1, CYG X-3 and GX 1+4

Abstract A high energy X-ray astronomy payload with phoswich scintillation detectors was flown from Hyderabad, India on December 18, 1984. Five galactic X-ray sources, Sco X-1, Cyg X-1, Gx 5-1, Cyg X-3 and GX I+4 were observed. The timing data, with a high time resolution of 40 μs, were analysed for periodicities and quasi-periodic oscillations (QPOs). GX 1+4 was in a low luminosity state and showed pulsations with a period of 95.9 s. Its period derivative was calculated. Sco X-1 was found not to exhibit QPOs in 18–40 keV X-rays with a 90% confidence limit of 0.20 on amplitude. Spectra are presented for Sco X-1, Cyg X-1 and GX 5-1.

A high sensitivity phoswich scintillator X-ray telescope for hard X-ray (20 – 120 keV) astronomy from balloon platform

Abstract A large area (400 cm 2 ) low background X-ray telescope consisting of four collimated NaI/CsI scintillator phoswich detectors (each 100 cm 2 ) was built and successfully flown several times during 1980–1984. The phoswich configuration enables one to eliminate X-ray background produced by high energy atmospheric and cosmic gamma-rays. Combined with large area, small field of view (5° × 5°) and large exposure time that was possible due to an on-board telescope pointing programmer, for the 20 – 120 Kev energy range, 3σ sensitivity achieved was 5 × 10 −6 photon/cm 2 sec Kev for exposure time of 10 4 sec at observational altitude of 4 g/cm 2 . The Instrument characteristics, relevant details on pointing system, detector system, associated electronics and telemetry and in-flight performance in 1983 and 1984 are presented.

The observation of the galactic anticenter region by the balloon borne gamma-ray telescope Natalya-I

Abstract This paper presents the results of measurements of gamma radiation with energies above 5 MeV, from the galactic anticenter region. The balloon-borne gamma ray telescope “Natalya-I”, was launched on 6 November, 1980 from the Tata Institute of Fundamental Researchs Balloon Facility (Hyderabad, India) and reached ceiling altitude of 35 km. The results on the accelerator calibration of the telescope, using a “tagged” gamma ray beam are also presented.

New balloon-borne telescope system tical - Mark II for hard X-ray astronomy

Abstract For the study of hard X-rays (18–150 KeV) from the celestial X-ray sources, NaI/CsI phoswich scintillator telescopes have been flown from Hyderabad during the last decade. The NaI(Tl)/CsI(Na) scintillator phoswich with Pulse Shape Discrimination technique reduces the non X-ray background by a factor 10 at balloon altitudes. The new telescope TICAL Mark-II with 1000sq.cm area [5 mm thick NaI(Tl) and 50 mm thick CsI(Na) phoswich] had a sensitivity to detect a minimum flux of 2.2 × 10−6 photons/sq.cm sec KeV in the energy range 18–150 KeV for 104 s exposure; this allows study of several bright active galactic nuclei. The telescope had a microprocessor-based tracking system to automatically follow celestial sources in elevation and azimuth according to a predetermined schedule. Several galactic X-ray sources, mostly binary pulsars, and the quasar 3C273 have been studied. The scintillator phoswich X-ray detector, the X-ray telescope and the electronic systems of the TICAL Mark II will be described.

Soviet-Indian research of cosmic radiation by high altitude balloons

The report presents some results on the cosmic radiation intensity research carried out with the high-altitude balloons for the period of 1977–1979. The intensity of gamma-radiation with the energy above 40 MeV was measured in two balloon flights at an altitude of 4–7 g/cm2 of residual atmosphere in the vicinity of the geomagnetic equator. A temporal analysis of the intensity to discover fluctuations with periods in the range of 4–60 min was made. Quasi-periodic fluctuations of gamma-radiation intensity with 5 min periods, amplitude ∼20% and duration of several hours were discovered. Possible mechanisms of such fluctuation appearance are discussed. n nThe report gives the results of measuring downward, upward and horizontal electron fluxes in the vicinity of the equator. The obtained data and the data provided by satellites are compared. The report discusses the prospects of further joint Soviet-Indian research of cosmic gamma-radiation.