Infrared Monitoring of the Microquasar GRS 1915+105: Detection of Orbital and Superhump Signatures

We present the results of 7 years of K-band monitoring of the low-mass X-ray binary GRS 1915+105. Positive correlations between the infrared flux and the X-ray flux and X-ray hardness are demonstrated. Analysis of the frequency spectrum shows that the orbital period of the system is Porb = 30.8 ± 0.2 days. The phase and amplitude of the orbital modulation suggests that the modulation is due to the heating of the face of the secondary star. We also report another periodic signature between 31.2 and 31.6 days, most likely due to a superhump resonance. From the superhump period we then obtain a range for the mass ratio of the system, 0.05 < q < 0.12.