Doppler Monitoring of the WASP-47 Multiplanet System

Abstract

We present precise Doppler observations of WASP-47, a transiting planetary system featuring a hot Jupiter with both inner and outer planetary companions. This system has an unusual architecture and also provides a rare opportunity to measure planet masses in two different ways: the Doppler method, and the analysis of transit-timing variations (TTV). Based on the new Doppler data, obtained with the Planet Finder Spectrograph on the Magellan/Clay 6.5m telescope, the mass of the hot Jupiter is $370 \pm 29~M_{\oplus}$. This is consistent with the previous Doppler determination as well as the TTV determination. For the inner planet WASP-47e, the Doppler data lead to a mass of $12.2\pm 3.7~ M_{\oplus}$, in agreement with the TTV-based upper limit of $<$22~$M_{\oplus}$ ($95\%$ confidence). For the outer planet WASP-47d, the Doppler mass constraint of $10.4\pm 8.4~M_{\oplus}$ is consistent with the TTV-based measurement of $15.2^{+6.7}_{-7.6}~ M_{\oplus}$.