2017ApJ...839L...8M

The two most common techniques for measuring planetary masses-the radial velocity (RV) and the transit timing variation (TTV) techniques-have been observed to yield systematically different masses for planets of similar radii. Following Steffen, we consider the effects of the observational biases of the two methods as a possible cause for this difference. We find that at short orbital periods (P 11 day), the two methods produce statistically similar results, whereas at long periods (P 11 day) the RV masses are systematically higher than the TTV ones. We suggest that this is consistent with an RV detection-sensitivity bias for longer periods. On the other hand, we do find an apparently significant difference between the short- and the long-period planets, obtained by both observing techniques-the mass-radius relationship parameterized as a power law has a steeper index at short periods than at long periods. We also point out another anticipated observational bias between the two techniques-multiple-planet systems with derived RV masses have substantially larger period ratios than the systems with TTV mass derivation.