Measurement of the Rossiter--McLaughlin Effect in the Transiting Exoplanetary System TrES-1

Abstract

We report a measurement of the Rossiter--McLaughlin effect in the transiting extrasolar planetary system TrES-1, via simultaneous spectroscopic and photometric observations with the Subaru and MAGNUM telescopes. By modeling the radial velocity anomaly that was observed during a transit, we determine the sky-projected angle between the stellar spin axis and the planetary orbital axis to be $\hat{I}»=30\pm 21$ [deg]. This is the third case for which $\hat{I}»$ has been measured in a transiting exoplanetary system, and the first demonstration that such measurements are possible for relatively faint host stars ($V\sim 12$, as compared to $V\sim 8$ for the other systems). We also derive a time of mid-transit, constraints on the eccentricity of the TrES-1b orbit ($e=0.048\pm 0.025$), and upper limits on the mass of the Trojan companions ($\lesssim$14 $M_{\oplus }$) at the 3$\ddot{I}ƒ$ level.

8 pages, 5 figures, 2 tables. Published in PASJ. Corrected typos