HARD X-RAY TAIL DISCOVERED IN THE CLOCKED BURSTER GS 1826-238

The low-mass X-ray binary (LMXB) neutron star (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 similar to 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. Most previously reported spectra with hard tails in LMXB NS have had an electron temperature of a few keV and a hard tail dominating above similar to 50 keV with an index of Gamma similar to 2-3. GS 1826-238 was found to have a markedly different spectrum with kT(e) similar to 20 keV and a hard tail dominating above similar to 150 keV with an index of Gamma similar to 1.8, more similar to black hole X-ray binaries. We report on our search for long-term spectral variability over the 25-370 keV energy range and on a comparison of the GS 1826-238 average spectrum to the spectra of other LMXB NSs with hard tails.