B9.5V

Cowley69 and Cowley72 used Ome^2 Aqr as their B9.5V standard.

Skiff08 lists only two B9.5V standards: HD 19805 and HD 23873

# No Standard
Garrison67 did not list a B9.5V standard. 

# Standards
HD 222661 = ome^2 Aqr = 105 Aqr = GJ 9836A = HR 8988
  B9.5V: JM53,Cowley69(stan),Cowley72(stan),Houk88,Abt02
  B9.5IV: Abt95,Gray87
  B9V: deVaucouleur57
  Notes: 5.4" binary,deltaV=6.0,A is SB (Worley96),Gahm83 calls "B" a A5Vne
  Hipparcos par=21.16+-0.87 mas => D=47.3+-1.9 pc
  D(ZAMS) = 43+-10 pc; hence near ZAMS!
  B-V(HIP)=-0.032+-0.004
  Johnson66: B-V=-0.04,U-B=-0.13
  Av(Neckel80)=0.02
  Mermilliod91: B-V=-0.041+-0.006, U-B=-0.121+-0.014
  Mamajek: (B-V)o=-0.018, E(B-V)=-0.023
  probably "reddened" by secondary since d ~ 47 pc.
  Note that Castelli reddening gives Av=0.39, where Shobbrook gives Av=0.04. 

HD 108767 = del CrV = HR 4757
  B9V: MK43,Jaschek64(all),Murphy69
  B9Vn: Cowley69
  B9.5V: Abt81,Gahm83,Houk88,Mora01
  B9.5IV-n: GrayGarrison87
  A0: Cannon
  M91: V=2.948+-0.010, B-V=-0.046+-0.005, U-B=-0.079+-0.017
  =>QBV=> (B-V)o=-0.036, (U-B)o=-0.080, E(B-V)=-0.010, T=9940
  delta(V)=5.5 binary
  So it looks like this this is now a B9.5, and most say dwarf

# Other standards
HD 19805 = HIP 14980 = Cl Melotte 20 167 (in alpha Per cluster)
  B9.5V: Morgan71,Jaschek78,MK78,Keenan85(see note)
  A0Va+: Gray87
  A0Vsp:Si: Abt78
  A1V: Petrie67
  B-V(HIP)=0.125+-0.008 
  Mermilliod91: B-V=0.121, U-B=0.030
  Mamajek vers. of Q-method: (B-V)o=-0.040, E(B-V)=0.161,Av=0.530,D(ZAMS)=181+-40 pc
  Alpha Per cluster member, so d ~ 180 pc with sig. reddening.
  Note: seems to be OK B9.5V standard except for Gray87,Abt78 call, but definitely blue
  Keenan85 lists "HD 19803" as a B9.5V standard, but this appears to be a typo for HD 19805

HD 23873 = Cl Melotte 22 2263 (Pleiades member)
  B9.5V: MK78, Gray87(B9.5Va),Mendoza56
  B9.5IVsn: Abt78
  A0V: : JM53
  B-V(HIP)=-0.027+-0.004
  Mermilliod91: B-V=-0.027+-0.004, U-B=-0.120+-0.000 
  Mamajek vers. of Q-method: B-Vo=-0.053, E(B-V)=0.026,D(ZAMS)=128+-29 pc (hence MS)
  par(HIP)=8.02+-0.91 mas
  Note: seems to be OK B9.5V standard

# B-Vo
-0.053 HD_23873
-0.040 HD_19805
-0.018 HD_222661