The quest for companions to post-common envelope binaries III. A reexamination of HW Virginis

We report new mid-eclipse times of the short-period sdB/dM binary HW Virginis, which differ substantially from the times predicted by a previous model. The proposed orbits of the two planets in that model are found to be unstable. We present a new secularly stable solution, which involves two companions orbiting HW Vir with periods of 12.7 yr and 55 +/- 15 yr. For orbits coplanar with the binary, the inner companion is a giant planet with mass M-3 sin i(3) similar or equal to 14 M-Jup and the outer one a brown dwarf or low-mass star with a mass of M-4 sin i(4) = 30-120 M-Jup. Using the mercury6 code, we find that such a system would be stable over more than 10(7) yr, in spite of the sizeable interaction. Our model fits the observed eclipse-time variations by the light-travel time effect alone, without invoking any additional process, and provides support for the planetary hypothesis of the eclipse-time variations in close binaries. The signature of non-Keplerian orbits may be visible in the data.