Measurement of the Surface Gravity of η Bootis

Direct angular size measurements of the G0 IV subgiant η Boo from the Palomar Testbed Interferometer are presented, with a limb-darkened angular size of θLD = 2.1894 mas, which indicates a linear radius of R = 2.672 ± 0.028 R☉. A bolometric flux estimate of Fbol = (22.1 ± 0.28) × 10-7 ergs cm-2 s-1 is computed, which indicates an effective temperature of Teff = 6100 ± 28 K and a luminosity of L = 8.89 ± 0.16 L☉ for this object. Similar data are established for a check star, HD 121860. The η Boo results are compared to, and confirm, similar parameters established by the MOST asteroseismology satellite. In conjunction with the mass estimate from the MOST investigation, a surface gravity of log g = 3.817 ± 0.016 [cm s-2] is established for η Boo.