O5.5V

MK73,MK78,Garrison94,Walborn90 do not list any O5.5V standards.

Walborn72 classified one star as a O5.5V variant: HD 14434
(O5.5Vn((f))p; V=8.5mag).

(B-V)(O5.5V) = -0.322 ; interp 
=> adopt (B-V)(O5.5V) = -0.322 [updated 2/7/2020]

(U-B)(O5.5V) = -1.145 ; interp
=> adopt (U-B)(O5.5V) = -1.145 [updated 2/7/2020]

Teff(O5.5V) = 39500 K ; Massey05(Milky Way)
Teff(O5.5V) = 39865 K ; Martins05(Obs. scale), GrayCorbally09
Teff(O5.5V) = 39972 K ; Simon-Diaz14 linear fit for O5.5V
Teff(O5.5V) = 40062 K ; Martins05(Theo. scale)
Teff(O5.5V) = 40470 K ; Holgado18
Teff(O5.5V) = 40500 K ; EEM trend for O dwarfs 1/2020
Teff(O5.5V) = 42150 K ; exemplar HD 93204
Teff(O5.5V) = 44000 K ; HD 48099-1 (Martins11)
=> adopt Teff(O5.5V) = 40500K (logTeff = 4.607) [updated 1/20/2020]

Mv(O5.5V) = -5.4  mag ; interp. from GrayCorbally09
Mv(O5.5V) = -5.39 mag ; HD 48099-1 (Mon OB2 member; Martins11)
Mv(O5.5V) = -5.35 mag ; Bowen08
Mv(O5.5V) = -5.22 mag ; EEM trend for O dwarfs
Mv(O5.5V) = -5.2  mag ; Conti71(ZAMS)
Mv(O5.5V) = -5.2  mag ; roughly interpolating O5V (-5.4) and O6V (-5.1)as f(Teff)
Mv(O5.5V) = -5.14 mag ; Martins06/obs.scale
Mv(O5.5V) = -5.12 mag ; Martins06/theor.scale
Mv(O5.5V) = -5.07 mag ; Martins05(both Theo. & Obs. scale)
Mv(O5.5V) = -5.0  mag ; Wegner07(halfway between O5V and O6V)
Mv(O5.5V) = -4.91 mag ; exemplar HD 93204
=> adopt Mv(O5.5V) = -5.2 mag [updated 2/8/2020]

BCv(O5.5V) =   -3.487 mag ; Balona94(Teff=40500K),set so BCv(5772K)=-0.085
BCv(O5.5V) =  -3.64  mag ; Martins06(obs.scale)
BCv(O5.5V) =  -3.65  mag ; Martins06(theor.scale)
BCv(O5.5V) = -3.665 mag ; EEM interp O5V(-3.76),O6V(-3.57)
BCv(O5.5V) =  -3.689 mag ; LanzHubeny03/07(Teff=40500K)
BCv(O5.5V) =  -3.70  mag ; Martins05(obs.scale)
BCv(O5.5V) =  -3.71  mag ; Martins05(theor.scale)
BCv(O5.5V) =   -3.954 mag ; Flower96(Teff=40500K),set so BCv(5772K)=-0.085
=> adopt BCv(O5.5V) = -3.67 [updated 1/31/2020]

logL(O5.5V) = 5.41  dex ; Martins05(Obs. & Theo. scale)
logL(O5.5V) = 5.432 dex ; EEM trend for O dwarfs O5.5V
logL(O5.5V) = 5.444 dex ; Mv=-5.2, BCv=-3.67 => Mbol = -8.870
logL(O5.5V) = 5.65  dex ; HD 48099-1 (Martins11)
=> adopt logL(O5.5V) =  5.444 dex [updated 2/8/2020]
=> adopt Mbol(O5.5V) = -8.870 mag [updated 2/8/2020]

logg(O5.5V) = 3.80 dex ; Holgado18
=> adopt logg(O5.5V) = 3.80 dex [updated 1/31/2020]

Rad(O5.5V) = 10.7088 Rsun ; Teff=40500K, logL=5.444
Rad(O5.5V) = 10.558 Rsun ; Martins05 (Teff=39866K,logL=5.404)
=> adopt Rad(O5.5V) =  10.709 Rsun [updated 2/8/2020]

Mass(O5.5V) = 30.0+-1.0 Msun ; FO15A Weidner10
Mass(O5.5V) = 37.8 Msun      ; MIST/Choi16 solar tracks for logT=4.607,logL=5.44
Mass(O5.5V) = 39+7-6 Msun    ; Weidner10
=> adopt Mass(O5.5V) = 38 Msun [updated 4/16/2022]

# Exemplar

HD 93204
  O5V((f)): Walborn73,Walborn02
  O5.5V(fc): Walborn10
 *O5.5V((f)): Sota14
  O6V((f)): Markova11
  O6/7V: Alexander18

  It appears that Walborn and subsequent authors moved this star 0.5-1
  subtype later than originally classified (O5V).
  V=8.440+-0.019(Mermilliod91), B-V=0.099+-0.010(Mermilliod91),
  U-B=-0.884+-0.005(Mermilliod91) => QBV =>
  (B-V)o=-0.333, (U-B)o=-1.188, E(B-V)=0.432, Av=1.392. E(B-V)=0.41(Savage01),
  E(B-V)=0.43(Snow94)
  Av=1.611+-0.032(MaizApellaniz18). plx=0.4486+-0.0378mas(GaiaDR2).
  Mv=-4.912. Teffs: 40000+-2000K(Garcia04), 40000K(Povich11),
  44300K(Snow94), 44000+-2000K(NebotGomez-Moran18) => <Teff> = 42150K.
  Mass=42.0Msun(Snow94), Mass=21.67Msun(Albacete-Colombo18).

# Other Stars

HD 14434 

HD 48099

HD 64315

HD 305525

NGC 6611 175

DH Cep