Stromgren photometry in M67

The photometry is calibrated using standards over a wide range in luminosity and temperature from NGC752 and zeroed to the standard system via published photoelectric observations. Relative to NGC752, differential offsets in reddening and metallicity are derived using astrometric members, supplemented by radial velocity information.

From single star members, offsets in the sense (M67-NGC752) are {delta}E(b-y)=-0.005{+/-}0.001(sem)mag from 327 F/G dwarfs and {delta}[Fe/H]=0.062{+/-}0.006(sem)dex from the combined m1 and hk indices of 249 F dwarfs, leading to E(b-y)=0.021{+/-}0.004(sem) and [Fe/H]M67=+0.030{+/-}0.016(sem) assuming [Fe/H]Hyades=+0.12. With probable binaries eliminated using c1, (b-y) indices, 83 members with ({pi}/{sigma}{pi})>50 generate (m-M)0=8.220{+/-}0.005(sem) for NGC752 and an isochronal age of 1.45{+/-}0.05Gyr.