F2IV

MK43 standard:            del Gem - F2IV
     			  zet Ser - F2IV 
JM53 standards:           bet Cas - F2IV
                          ups UMa - F2IV 
MorganAbt72 standards:    HR 1554 - F2IV
		          HR 8765 - F2IV
MK73 dagger standard:     1 Mon (=HR 2107) - F2IV
Cowley74 standards:       ups UMa - F2IV 
		          iot Leo - F2IV
		          HR 8765 - F2IV
Cowley76 standard:        iot Leo - F2IV
			  HR 8765 - F2IV
			  bet Cas - F2III-IV
MK78 standard:            bet Cas - F2III-IV
GrayGarrison89 standards: 32 Tau - F2IV [low vsini standard]

Garcia89 lists two F2IV standards: HD 40535 (1 Mon) and HD 84999 (ups
UMa), along with the F2III-IV standard HD 432 (bet Cas).

GrayGarrison89 explicitly exclude 1 Mon as a standard star.

(B-V)(F2IV) = 0.336 ; exemplar HD 150557 = 14 Oph
(B-V)(F2IV) = 0.345 ; pri. stan. HD 24740 = HR 1218
(B-V)(F2IV) = 0.356(+-0.015 sem,+-0.033 stdev) ; SIMBAD median F2IV d<75pc,V<6.5(N=10)
=> adopt (B-V)(F2IV) = 0.35 [updated 2/3/2022]

Mv(F2IV) = 1.9  ; GrayCorbally09
Mv(F2IV) = 2.03 ; exemplar HD 150557 = 14 Oph
Mv(F2IV) = 2.39 ; pri. stan. HD 24740 = 32 Tau
Mv(F2IV) = 2.44(+-0.20 sem,+-0.41 stdev) ; SIMBAD median F2IV d<75pc,V<6.5(N=10)

# No standards

There are no F2IV anchor points (Garrison94).
Houk88 does not list a F2IV standard. 

# Primary Standards

HD 24740 = HR 1218 = 32 Tau (J0356+2228)
 *F2IV: Jaschek78(Cowley74),GrayGarrison89(low vsini stan),Gray89,Gray01(F2IVs)
  F0IV: Paunzen01
  F3V: Adams35
  F0: Cannon

  GrayGarrison89 primary "F2IV" standard.
  V=5.62(HIP), B-V=0.345+-0.004(HIP).
  plx=22.5957+-0.0385mas(GaiaEDR3) => Mv=2.39 => 0.42 mag above MS. 

# Secondary Standards

HD 40535 = 1 Mon
  F2IV: MK73,Jaschek78(Morgan72)
 *F2III-IV: GrayGarrison89
  F2II: Bidelman51,Jaschek64(all)
  F0: Cannon

  Houk99 comments "HR 2107; 1 MON; V474 MON; ~SCT TYPE; 5.93-6.36V;
  0.13612600 DAY vSINi=25". In SMARTS list for 26/I and 47/I spectra. 

# Deprecated Standards

zet Ser = HR 6710 = HD 164259
  F0: Cannon
  F1V:  Adams35
  F2IV: MK43
 *F2V: Gray03 
  F2IV-V: Gray89
  F2IV: Houk99("SIMBAD type")
  F3V: 1937AnHar.105...45H,JM53,DeVaucouleurs57,Jaschek64(most),Cowley74(stan)
  F4V: Malaroda75
  F5III: 1978A&AS...35...75C

  Only F3V star mentioned in Johnson53, although not technically a
  standard.  Alternates between F2 and F3 too much to be really
  considered a good standard.
  
HD 432 = HR 21 = HIP 746 = bet Cas
  F2IV: JM53,Jaschek64(most),Cowley67
  F2III-IV: Morgan72,MK78(stan)
 *F2III: MK43,Gray89,GrayGarrison89,Gray01,Gray03(stan)
  F5: Cannon

  All published classifications since 1935 are "F2" subtype. Morgan
  flipflopped on luminosity class ("III" in MK43, "IV" in JM53,
  "III-IV" in MK78). Gray has consistently called it "F2III" in four
  publications, and considers it the "F2III" standard. I'm inclined
  to follow Gray and call it "F2III"

HD 84999 = ups UMa = HR 3888
  F2IV: JM53,Jaschek64(most),Peniche81
  F2III: MK43
  F0IV: Morgan72,GrayGarrison89
  F0: Cannon
  A9IV: Abt85

  Lots of disagreement in subtype and luminosity. 

HD 99028 = iot Leo = HR 4399 
  F2IV: Slettebak55(SB),Jaschek64(most,SB),Stephenson69,Cowley74(stan),Cowley76(stan)
  F2V: Roman49
  F4IV: Abt81
  F1IV+G3V: Edwards76 
  F3III: Levato78
  F3V: Abt09
  F5: Cannon
  F5IV: Gray03
  Only Cowley74 used this star as a standard.
  
  1.5" pair. Negligible agreement among different investigators.  Abt
  has been on three papers classifying this star - and all three types
  were different (F4IV,F3V,F3III).

HD 217754 = HR 8765
  F2IV: Morgan72(stan),Cowley74(stan),Cowley76(stan),Abt95
  F2Ib: Fehrenbach66(Kennedy83)
  F0IIp: Gray01(CaI 4227A strong)
  F0: Cannon
  Morgan72 and Cowley74 consider it a standard, but Gray01 disagrees 
  considerably with the type.

# Exemplars

HD 150557 = 14 Oph = HR 6205 = HIP 81734 
  F2III: Cowley76
 *F2IV+: Gray89,GrayGarrison89
  F2V: Houk99
  F2-4III-IV: BSC(Hoffleit91)
  F4IV: Cowley79

  V=5.74(HIP), B-V=0.336+-0.004(HIP), V-I=0.39+-0.02(HIP).
  plx=18.0784+-0.0472mas(GaiaEDR3) => Mv=2.03 =>
  0.73 mag above MS. 


# Other Stars

HD 11171 = chi Cet = HR 531
  F2III-IV: Gray03
  F2IV-V: GrayGarrison89

  several F2 classifications and the Gray classifications average out
  to F2IV.
  
HD 10472
 *F2IV: Pribulla14
  F2IV/V: Houk75

HD 51199 = HR 2590 
  F1.5V: Gray06
 *F2IV: Adams35,GrayGarrison89
  F2IV/V: Houk88
  F2V: 1937AnHar.105...45H
  F3V: Abt08

HD 164615
 *F2IV: Abt83
  F2IV-V: Harlan69
  F2IV/V: Grenier99

  Abt85 wrote whole paper just on this star: "HD 164615: A Probable
  Spotted Single F Type Star", mentioning light variations of 0.05 mag
  over period 0.815d. "spectrum is normal (F2IV)".

HD 205539
  F0/2V: 1979RA......9..479C
  F0IV: Cowley74
  F2IV: Grenier99
 *F2IVp: Abt95(CaI,MgII weak)
  F2IV/V: Abt69(lines weak)