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Table 2.

Number and frequency of possible isolated stars relative to nearby clusters or OB associations.

Sample Method 1 Method 2

dthresh, 1 = 74 pc Number Frequency Number Frequency
Only clusters
d.o.f. = 4 70 0.299 72 0.308
d.o.f. = 3 86 0.368 90 0.385
d.o.f. = 2 19 0.081 20 0.085
Whole sample 175 0.748 182 0.778

Only OB associations
d.o.f. = 4 81 0.346 87 0.372
d.o.f. = 3 92 0.393 94 0.402
d.o.f. = 2 15 0.064 16 0.068
Whole sample 188 0.803 197 0.842

Clusters + OB associations
d.o.f. = 4 66 0.282 69 0.295
d.o.f. = 3 80 0.342 85 0.363
d.o.f. = 2 13 0.056 15 0.064
Whole sample 159 0.679 169 0.722

dthresh, 2 = 204pc Number Frequency Number Frequency

Only clusters
d.o.f. = 4 35 0.149 40 0.171
d.o.f. = 3 57 0.244 68 0.291
d.o.f. = 2 9 0.038 11 0.047
Whole sample 101 0.432 119 0.509

Only OB associations
d.o.f. = 4 64 0.274 71 0.303
d.o.f. = 3 84 0.359 91 0.389
d.o.f. = 2 11 0.047 13 0.056
Whole sample 159 0.679 175 0.748

Clusters + OB associations
d.o.f. = 4 26 0.111 33 0.141
d.o.f. = 3 49 0.209 62 0.265
d.o.f. = 2 4 0.017 8 0.034
Whole sample 79 0.338 103 0.440

Notes. Number and frequency of possible isolated stars relative to nearby star clusters or OB associations, given the threshold distance of dthresh, 1 = 74 pc and dthresh, 2 = 204 pc. Method 1 only takes the de-projected positions of stars, clusters and OB associations into account, while method 2 considers stellar groups whose age difference to the stars is 5 Myr at most. The frequencies are normalized to the total sample of stars.

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