A period decrease in the sdB eclipsing binary system HW Vir

Observations of eclipses of HW Vir $$( = \text {BD} - 7^\circ3477)$$ over a 9-yr baseline show that the period is decreasing. The overall nature of the decrease cannot yet be seen, but we briefly discuss the possible causes and rule out gravitational radiation effects, rotation of the line of apsides and mass transfer. A third body in the system could be the cause of an apparent period change, though this should be observationally testable over a few more seasons. Angular momentum loss via magnetic braking in a modest stellar wind seems the most likely possibility for the period decrease.