Low-energy gamma-ray spectrum of Scorpius X-1

A 2-hour balloon altitude observation of Sco X-1, in the -keV energy band, was conducted from Argentina on 1970 November 25. The -keV data are consistent with an extension of the lowenergy exponential spectrum. In addition, a penetrating component was detected at higher energies. The energy - flux power law 0.4U(6.6 +6.1) and the expression 0.02 exp [-E/190(+180, -90)] keV 1 keV-1 are equally acceptable approximations to this latter component in the 35- energy interval. The spectrum is lost in the background at energies greater than 300 keV, where upper limits are established.