GRS 1124−683

Lore & Background

GRS 1124−683 was discovered when the system produced an outburst of X-rays on January 9, 1991, detected by the orbiting X-ray telescopes Granat and Ginga. The system is an X-ray nova, which periodically produces bright outbursts of X-rays, visible light, and other forms of energy. In such a system, a black hole pulls gas from the surface of a companion star, forming a thin accretion disk. During the January 20–21, 1991 outburst, radiation was produced by positron annihilation, and the SIGMA telescope aboard GRANAT detected a relatively narrow variable emission line near 500 keV in the spectrum. From January 9 to August 14, 1991, the spectrum had a strong hard component extending up to ~300 keV.

Reader's Guide

GRS 1124−683 is significant as a well-studied example of a black hole candidate in an X-ray nova system. Its discovery by the Granat mission and Ginga highlighted the role of X-ray astronomy in identifying black holes via accretion-driven outbursts. The system's parameters—a black hole about seven times the Sun's mass and a companion three-quarters the Sun's mass—provide constraints on stellar evolution and black hole formation. The detection of a positron annihilation line near 500 keV during its outburst offers insight into high-energy processes near black holes. As one of several likely black hole X-ray novae, it contributes to the understanding of how such systems cycle between quiescence and outburst, and how gas accretion onto black holes produces observable radiation across the electromagnetic spectrum.

Did You Know?

• GRS 1124−683 was discovered by the Granat mission and Ginga on January 9, 1991.
• The black hole in the system is about seven times as massive as the Sun.
• The companion star is three-quarters as massive as the Sun and cooler, with one-third the Sun's luminosity.
• During the January 20–21, 1991 outburst, a variable emission line near 500 keV from positron annihilation was detected.