We have used the Sydney University Stellar Interferometer (SUSI) to measure
the angular diameter of the F9 V star beta Virginis. After correcting for limb
darkening and combining with the revised Hipparcos parallax, we derive a radius
of 1.703 +/- 0.022 R_sun (1.3%). We have also calculated the bolometric flux
from published measurements which, combined with the angular diameter, implies
an effective temperature of 6059 +/- 49 K (0.8%). We also derived the
luminosity of beta Vir to be L = 3.51 +/- 0.08 L_sun (2.1%). Solar-like
oscillations were measured in this star by Carrier et al. (2005) and using
their value for the large frequency separation yields the mean stellar density
with an uncertainty of about 2%. Our constraints on the fundamental parameters
of beta Vir will be important to test theoretical models of this star and its
oscillations.Comment: accepted for publication in MNRAS. Updated reference