Abstract
We present broad-band UBVc CCD imagery of 334 stars in the direction of the Galactic cluster Haffner 19. The sample is complete to m[ λ ]= 19 ( λ = U, B, V, R, I). We reliably establish the cluster membership for 102 stars based upon their locations in the ( V, bv ), ( V, si ), ( I, ri ), ( ub, bv ), and ( sr, si ) diagrams, thus increasing three-fold the number of known cluster members. With the Q-method we determine the MK spectral types of the 33 brightest stars, confirming that 29 belong to the cluster's young population (15 B0-B1 and 14 B2-B9 main sequence stars). Complementary uvby β photoelectric photometry of 6 bright stars independently confirms the distance and reddening to the cluster. Our narrow-band H α, [N II], and [S II] imagery reveals the presence of a Strömgren sphere and we derive its properties. From our photometric data and by four different means we find that the best distance estimate to the cluster is 5.2+/-0.4 kpc, with a fairly homogeneous reddening of E[bv ]= 0.42+/-0.01. The data constrain the age of the cluster to be between 106 and <= 3.7×106 years, with 2×106 yr as its most likely estimate. Because of its young age, it is not possible to derive a reliable estimate for its metallicity. Finally, we present radial velocities of Haffner 18ab, Haffner 19, and NGC 2467, which place the last two of these at the same distance.
