Spectral measurements of galactic and extragalactic sources in the hard X-ray region of 20-200 keV using balloon borne telescope
Author: Manchanda, R.K.
Source: Astrophysics and Space Science, Volume 282, Number 1, 2002 , pp. 149-160(12)
The spectral and temporal measurements in the hard X-ray region between 20-200 keV not only determines the extended behaviour of thermal X-ray spectrum below 10 keV but also provide a unique insight into the non-thermal processes in relativistic astrophysical plasma. From our present understanding of the X-ray sources, a significant flux in the 20-200 keV band is expected from a variety of astrophysical phenomena, however, the available spectral data on the galactic and extragalactic X-ray source is very limited. This is mainly due to the fact that sensitivity of the detector systems used for earlier measurements was relatively poor. Since 1997, we have been carrying out a programme of hard X-ray observations galactic and extragalactic sources, in the 20-200 keV energy band using a highly sensitive balloon borne experiment. The X-ray telescope consists of three modules of large area scintillation counters specially configured in the back-to-back geometry and have a combined sensitivity of ∼ 10-6 ph cm-2 s-1 keV-1 for an on-source observations of 3 hrs. A total of 30 hours of ceiling data above an altitude of 3 mbar has been collected in 4 successful balloon flights from Hyderabad, India. Almost a dozen galactic and extragalactic X-ray sources were targeted and tracked during these observations. A positive detection was made in each case and in some cases the observed spectra extended right up to 150 keV. A brief account of the observed spectral and temporal features on some of the sources along with accurate measurement of diffuse background spectrum and a weak gamma ray burst will be presented in the paper.
Document Type: Research Article
Affiliations: Tata Institute of Fundamental Research, Mumbai-400 005, India; E-mail: firstname.lastname@example.org
Publication date: 2002-01-01