Observations of Sco X-1 source in 16 -110 keV range

Abstract

The properties of Sco X-I X-ray source have been studied in the energy interval 16-111 keY using balloon-borne X-ray detectors. The X-ray telescope consisted of a NaI(Tl) crystal with an area of 97.3 ern" and 4 mm thick surrounded by cylindrical active and passive collimators with a field of view of 18.6° FWHM. The telescope was mounted on an orienting platform with its axis at 310 to the zenith and it scanned an annulus in the sky in each rotation. The balloon flight was made from Hyderabad (lat. 17.6° N and long. 78.5° E) India, on April 16, 1969. The data obtained from this flight were combined with those from the earlier flights on April 28, 1968 and December 22, 1968 using the same instrument. It is found that in the energy interval 16-111 KeY, the spectrum can be represented either (i) by the exponential form N(E)dE = (K/E)e-^EJEodE with E_o = 5 keY, in the energy range 15-40 keY, and E_o ≈ 30 keY in the 40-110 keY range, or (ii) by a power spectrum of the form N(E)dE = CiE^-x, where ex = 4.5 ± 0.5 over the entire energy range. The flux in the energy interval 16-47 keY was found to be almost steady for a period of one hour on April 16, 1969. The results from other X-ray sources will be presented later.