Astrophys. J., 576, 880-893 (2002/September-2)
The star formation history and mass function of the double cluster h and χ Persei.
SLESNICK C.L., HILLENBRAND L.A. and MASSEY P.
Abstract (from CDS):
The h and χ Per ``double cluster'' is examined using wide-field (0°.98x0°.98) 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±0.01], distance moduli (11.85±0.05), and ages (12.8±1.0 Myr) for the two clusters. In addition, we find an initial mass function slope for each of the cluster nuclei that is quite normal for high-mass stars, Γ=-1.3±0.2, indistinguishable from a Salpeter value. We derive masses of 3700 M☉(h) and 2800 M☉(χ) integrating the present-day mass function from 1 to 120 M☉. 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.
Galaxy: Open Clusters and Associations: Individual: NGC Number: NGC 869 - Galaxy: Open Clusters and Associations: Individual: NGC Number: NGC 884 - Stars: Early-Type - Stars: Luminosity Function, Mass Function
VizieR on-line data:
<Available at CDS (J/ApJ/576/880): table1.dat table2.dat table3.dat>
Catalog: [SHM2002] NNNN N=4528.
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