The 2:1 resonant exoplanetary system orbiting HD 73526

We report the detection of a second exoplanet orbiting the G6 V dwarf HD 73526. This second planet has an orbital period of 377 days, putting it in a 2:1 resonance with the previously known exoplanet, the orbital period for which is updated to 188 days. Dynamical modeling of the combined system allows solution for a self-consistent set of orbital elements for both components. HD 73526 is the fourth exoplanetary system (of a total of 18 systems with two or more components currently known) to have components detected in 2:1 resonance. Finding such a large fraction of multiple planets (more than 20%) in 2:1 resonance strongly suggests that orbital migration, halted by stabilization in a trapping resonance, plays an important role in the evolution of exoplanets in multiple planet systems.