NEW OBSERVATIONAL CONSTRAINTS ON THE υ ANDROMEDAE SYSTEM WITH DATA FROM THE<i>HUBBLE SPACE TELESCOPE</i>AND HOBBY-EBERLY TELESCOPE

Abstract

We have used high-cadence radial velocity (RV) measurements from the Hobby-Eberly Telescope with existing velocities from the Lick, Elodie, Harlan J. Smith, and Whipple 60'' telescopes combined with astrometric data from the Hubble Space Telescope Fine Guidance Sensors to refine the orbital parameters and determine the orbital inclinations and position angles of the ascending node of components υ And A c and d. With these inclinations and using M* = 1.31M☉ as a primary mass, we determine the actual masses of two of the companions: υ And A c is 13.98+2.3−5.3 MJUP, and υ And A d is 10.25+0.7−3.3 MJUP. These measurements represent the first astrometric determination of mutual inclination between objects in an extrasolar planetary system, which we find to be 299 ± 1°. The combined RV measurements also reveal a long-period trend indicating a fourth planet in the system. We investigate the dynamic stability of this system and analyze regions of stability, which suggest a probable mass of υ And A b. Finally, our parallaxes confirm that υ And B is a stellar companion of υ And A.