Abstract:
Membership identification is the first step in determining the properties of a star cluster. Low-mass members in
particular could be used to trace the dynamical history, such as mass segregation, stellar evaporation, or tidal
stripping, of a star cluster in its Galactic environment. We identified member candidates of the intermediate-age
Praesepe cluster (M44) with stellar masses ∼0.11–2.4 Mꙩ , using Panoramic Survey Telescope And Rapid Response
System and Two Micron All Sky Survey photometry, and PPMXL proper motions. Within a sky area of 3° radius,
1040 candidates are identified, of which 96 are new inclusions. Using the same set of selection criteria on field stars,
an estimated false positive rate of 16% was determined, suggesting that 872 of the candidates are true members.
This most complete and reliable membership list allows us to favor the BT-Settl model over other stellar models.
The cluster shows a distinct binary track above the main sequence, with a binary frequency of 20%–40%, and a
high occurrence rate of similar mass pairs. The mass function is consistent with that of the disk population but
shows a deficit of members below 0.3 solar masses. A clear mass segregation is evidenced, with the lowest-mass
members in our sample being evaporated from this disintegrating cluster.
