Hard X-ray Tail Discovered in the Clocked Burster GS 1826-238

Understand

The LMXB NS GS 1826-238 was discovered by Ginga in 1988 September.

• Due to the presence of quasi-periodicity in the type I X-ray burst rate, the source has been a frequent target of X-ray observations for almost 30 years.
• Though the bursts were too soft to be detected by INTEGRAL/SPI, the persistent emission from GS 1826-238 was detected over 150 keV during the ~10 years of observations.
• Spectral analysis found a significant high-energy excess above a Comptonization model that is well fit by a power law, indicating an additional spectral component.