SIMBAD references

Precision uvbyCaHβ photometry of the metal-deficient, old open cluster NGC 2506 is presented. The survey covers an area of 20^′×20^′ and extends to V∼18 for b - y and Hβ and to V∼17.0 for c₁ and hk. For V brighter than 16.0, photometric scatter among the indices leads to the recovery of six known variables within the cluster core and five new variables in the outer 5^′ of the survey field. Proper motions, radial velocities, and precise multicolor indices are used to isolate a highly probable sample of cluster members from the very rich color-magnitude diagram. From 257 highly probable members at the cluster turnoff, we derive a reddening estimate of E(b-y)=0.042±0.001 (E(B-V)=0.058±0.001), where the errors refer to the internal standard errors of the mean. [Fe/H] is derived from the A/F dwarf members using both m₁ and hk, leading to [Fe/H] = -0.296 ± 0.011 (sem) and -0.317 ± 0.004 (sem), respectively. The weighted average, heavily dominated by hk, is [Fe/H] = -0.316 ± 0.033. Based on red giant members, we place an upper limit of ±0.010 on the variation in the reddening across the face of the cluster. We also identify two dozen potential red giant cluster members outside the cluster core. Victoria-Regina isochrones on the Stromgren system produce an excellent match to the cluster for an apparent modulus of (m-M)=12.75±0.1 and an age of 1.85 ± 0.05 Gyr.