The Planetary Mass-Radius Relation and Its Dependence on Orbital Period as Measured by Transit Timing Variations and Radial Velocities

• Published in: Astrophysical journal. Letters 2017-04, Vol.839 (1), p.L8-L8
• Main Authors: Mills, Sean M., Mazeh, Tsevi
• Format: Article
• Language: English
• Subjects: Bias; Derivation; Orbits; Planets; planets and satellites: detection; Production methods; Radial velocity; techniques: photometric; techniques: radial velocities; Time measurements; Transit
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/aa67eb

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 ( day), the two methods produce statistically similar results, whereas at long periods ( 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.