O3.5V

There are no O3.5V anchor (Garrison94) or dagger (MK73) standards.

Walborn02 defined the O3.5V type. 

Walborn02 primary standards: HD 93128 (O3.5V), HD 93129B (O3.5V).

U-B(O3.5V) = -1.052 ; pri. stan. HD 93129B (Q-method)
U-B(O3.5V) = -1.147 ; pri. stan. HD 93128 (Q-method)
U-B(O3.5V) = -1.17  ; interp
U-B(O3.5V) = -1.185 ; exemplar HD 93205 (Q-method)
=> adopt (U-B)(O3.5V) = -1.17 [updated 2/7/2020]

B-V(O3.5V) = -0.322 ; pri. stan. HD 93128 (Q-method)
B-V(O3.5V) = -0.328 ; U-B=-1.17 trend/Q-method
=> adopt (B-V)(O3.5V) = -0.328 [updated 2/7/2020]

Teff(O3.5V) = 43710 K ; Holgado18
Teff(O3.5V) = 43856 K ; Martins05
Teff(O3.5V) = 44100 K ; EEM trend for O dwarfs **
=> adopt Teff(O3.5V) = 44100 K (logTeff = 4.644) [updated 1/20/2020]

logg(O3.5V) = 3.76 dex ; Holgado18
=> adopt logg(O3.5V) = 3.76 dex [updated 1/31/2020]

BCv(O3.5V) =  -3.986 mag ; Martins05
BCv(O3.5V) = -3.96  mag ; EEM interp O3V(-4.03),O4V(-3.89)
BCv(O3.5V) =  -3.93  mag ; Martins06(theor.scale)
BCv(O3.5V) =  -3.928 mag [Teff=43710K; last updated 8/3/2018, adjusted so that BCv(5772K)=-0.08]
BCv(O3.5V) =  -3.92  mag ; Martins05(obs.scale)
=> adopt BCv(O3.5V) = -3.96 [updated 1/31/2020]

logL(O3.5V) = 5.736 dex ; EEM trend for O dwarfs
logL(O3.5V) = 5.750 dex ; Martins05
logL(O3.5V) = 5.760 dex ; Mv=-5.70, BCv=-3.96 => Mbol=-9.66
=> adopt logL(O3.5V) =  5.760 dex [updated 2/8/2020]
=> adopt Mbol(O3.5V) = -9.660 mag [updated 2/8/2020]

Mv(O3.5V) = -5.648 mag ; Martins05
Mv(O3.5V) = -5.670 mag ; EEM trend for O dwarfs
Mv(O3.5V) = -5.705 mag ; Martins06/theor.scale
Mv(O3.5V) = -5.715 mag ; Martins06/interp.scale
Mv(O3.5V) = -5.76  mag ; pri. stan. HD 93128 
=> adopt Mv(O3.5V) = -5.70 [updated 2/7/2020]

Rad(O3.5V) = 12.9950 Rsun ; logL=5.760, Teff=44100K
Rad(O3.5V) = 12.985 Rsun ; Martins05 (Teff=43856K,logL=5.750)
=> adopt Rad(O3.5V) = 12.995 Rsun [updated 2/8/2020]

Mass(O3.5V) = 54.7 Msun   ; MIST/Choi16 solar tracks for logT=4.644,logL=5.76
Mass(O3.5V) = 59+7-6 Msun ; Weidner10
=> adopt Mass(O3.5V) = 55 Msun [updated 4/16/2022]

# Primary Standards

HD 93128 = Cl Trumpler 14 2 = Cl* Trumpler 14 MJ 157 = 2MASS J10435441-5932574
 *O3.5V((fc))z: Sota14
  O3.5V((f+)): Walborn02
  O3V((f)): Walborn72
  O4V: Vijapurkar93
  O4:V: Morrell88
  O3((f)): Conti77
  Of:: Houk75

  In Trumpler 14 region in Car OB1.  Schull19 estimates unreddened
  Vo=6.532, Av=2.243.  Mermilliod91: V=8.817+-0.033, B-V=0.247+-0.005,
  U-B=-0.740. Using Q-method, I get: (B-V)o=-0.322, (U-B)o=-1.147,
  E(B-V)=0.569, Av=1.841 for standard Rv(Cox00 calibration). Using
  GaiaDR2 astrometry for 29 O-stars in CarOB1, Schull19 estimates mean
  distance 2.87+-0.73 pc (photometric distance 2.60+-0.28 kpc).
  2.87kpc => (m-M)o=12.289, plx=0.348mas.  For Vo=6.532, D=2.87kpc =>
  Mv=-5.76.

HD 93129B
  O3.5V((f+)): Walborn02
  O3.5V((f)): Sota14
 *O3.5V((f))z: MaizAppelaniz16
  O3V((f)): Walborn73
  
  Secondary to a O2If* primary (HD 93129A) 2.8" away.
  V=10.745+-0.055, B-V=0.290+-0.030, U-B=-0.630+-0.020(Mermilliod91) =>
  Q-method(1/2020) => (B-V)o=-0.295, (U-B)o=-1.052, E(B-V)=0.585, Av=1.897.

# Exemplars

HD 93205 = LS 1849
  O3.5V((f+))+O8V: Walborn02
 *O3.5V((f))+O8V: Sota14
  O3V+O8V: Morrell01
  O3+O8:: Conti76
  O3: Conti77
  O3V: Walborn71

  V=7.748+-0.004, B-V=0.062+-0.015, U-B=-0.908+-0.004(Mermilliod91)
  => Q-method(1/2020) => (B-V)o=-0.332, (U-B)o=-1.185, E(B-V)=0.394,
  Av=1.270. 

# Other Stars

HD 93250
  O3.5V((f+))+O8V: Walborn02
  O3V((f)): Walborn71
  O3: Conti77
 *O4IV(fc): MaizAppelaniz16
  O4III(fc): Sota14
  O5: Morgan55
  O6/7: Houk75