2016MNRAS.457.1028S

We have obtained membership probabilities of stars within a field of from the centre of the open cluster Alpha Persei using proper motions and photometry from the PPMXL and Wide-field Infrared Survey Explorer catalogues. We have identified 810 possible stellar members of Alpha Persei. We derived the global and radial present-day mass function (MF) of the cluster and found that they are well matched by two-stage power-law relations with different slopes at different radii. The global MF of Alpha Persei shows a turnover at m = 0.62 M☉ with low- and high-mass slopes of αlow = 0.50 ± 0.09 (0.1 < m/ M☉ < 0.62) and αhigh = 2.32 ± 0.14 (0.62 <= m/ M☉ < 4.68), respectively. The high-mass slope of the cluster increases from 2.01 inside 110 to 2.63 outside 22, whereas the mean stellar mass decreases from 0.95 to 0.57 M☉ in the same regions, signifying clear evidence of mass segregation in the cluster. From an examination of the high-quality colour-magnitude data of the cluster and performing a series of Monte Carlo simulations, we obtained a binary fraction of fbin = 34 ± 12 per cent for stars with 0.70 < m/ M☉ < 4.68. This is significantly larger than the observed binary fraction, indicating that this open cluster contains a large population of unresolved binaries. Finally, we corrected the MF slopes for the effect of unresolved binaries and found low- and high-mass slopes of αlow = 0.89 ± 0.11 and αhigh = 2.37 ± 0.09 and a total cluster mass of 352 M☉ for Alpha Persei.