GJ 436b and XO-1b transits

We search for additional planets in the systems of the hot Neptune GJ 436b, and the hot-Jupiter XO-1b, using high cadence observations in the J and KS bands. New high-precision transit timing measurements are reported: GJ 436b Tc=2454238.47898+/-0.00046HJD; XO-1b Tc(A)=2454218.83331+/-0.00114HJD, Tc(B)=2454222.77539+/-0.00036HJD, Tc(C)=2454222.77597+/-0.00039HJD, Tc(D)=2454226.71769+/-0.00034HJD, and they were used to derive new ephemeris.

We also determined depths for these transits. No statistically significant timing deviations were detected. We demonstrate that the high cadence ground based near-infrared observations are successful in constraining the mean transit time to 30s, and are a viable alternative to space missions.