The h and \chi Per “ double cluster ” is examined using wide-field ( 0.98 ^ { \circ } \times 0.98 ^ { \circ } ) CCD UBV imaging supplemented by optical spectra of several hundred of the brightest stars .
Restricting our analysis to near the cluster nuclei , we find identical reddenings ( E ( B - V ) = 0.56 \pm 0.01 ) , distance moduli ( 11.85 \pm 0.05 ) , and ages ( 12.8 \pm 1.0 Myr ) for the two clusters .
In addition , we find an IMF slope for each of the cluster nuclei that is quite normal for high-mass stars , \Gamma = -1.3 \pm 0.2 , indistinguishable from a Salpeter value .
We derive masses of 3700 \cal M _ { \odot } ( h ) and 2800 \cal M _ { \odot } ( \chi ) integrating the PDMF from 1 to 120 \cal M _ { \odot } .
There is evidence of mild mass segregation within the cluster cores .
Our data are consistent with the stars having formed at a single epoch ; claims to the contrary are very likely due to the inclusion of the substantial population of early-type stars located at similar distances in the Perseus spiral arm , in addition to contamination by G and K giants at various distances .
We discuss the uniqueness of the double cluster , citing other examples of such structures in the literature , but concluding that the nearly identical nature of the two cluster cores is unusual .
We fail to settle the long-standing controversy regarding whether or not the double cluster is the core of the Per OB1 association , and argue that this may be unanswerable with current techniques .
We also emphasize the need for further work on the pre-main sequence population of this nearby and highly interesting region .