Outburst, identification, and X-ray light curve of GS 1354 - 64 (= MX 1353 - 64?, Centaurus X-2?)

Abstract

This paper describes the optical identification and the X-ray light curve of an ultrashort transient X-ray source, GS 1354 - 64, discovered on February 13, 1987 by the All Sky Monitor (ASM) on onboard Ginga satellite. The data obtained by ASM are supplemented by data from the ESO 1-m Schmidt and the 1.54-m Danish telescopes, showing that the X-ray spectrum of the GS 1354 - 64 consists of two components: a disk blackbody spectrum with a temperature of 0.7 keV and a power-law component with a photon index of 2.1, which is one of the characteristics of the black hole candidates. It is shown that, although the position of the GS 1354 - 64 source is consistent with the positions of two X-ray outbursts, MX 1353 - 64 and Cen X-2, the characteristics of GS 1354 - 64 are markedly different from either of these sources.