The I band light curve of the low mass x‐ray binary GX 9+9

Abstract

The I‐band light curve of GX 9+9 shows a roughly sinusoidal modulation. The best fitting sine‐wave has a period and formal error of 4.1744±0.0002 hours. When the data are folded on this period, however, clear variations in the shape of the light curve are apparent from night to night. The modulation in the mean light‐curve has a semi‐amplitude of 10.6%.