F0IV

57 Tau appears to be the best available primary F0IV standard, 
with eps Cep as a good secondary standard. mu Cet should probably be
avoided. 

There are no F0IV anchor points (Garrison94), indeed no subgiant
anchors earlier than G0IV. Garcia89 lists 3 F0IV standards: HD 17094
(mu Cet), HD 27397 (57 Tau), and HD 211336 (eps Cep).

Similar to the late As, F0IV subgiant standards tend to be not far from
the main sequence. 

Comments on color trends of F subgiants vs. F dwarfs are appended at
the end of this file.

JM53 standard:            mu Cet - F0IV
			  eps Cep - F0IV 
JM53 non-standard:        zet02 Lyr - F0IV
MorganAbt72 standard:     del Aql (=HR 7377) - F0IV
MK73 standard:            57 Tau (=HR 1351) - F0IV
Cowley74 standards:       57 Tau - F0IV
			  mu Cet - F0IV
			  eps Cep - F0IV
Cowley76 standard:        del Aql - F0IV
MK78 standard:            57 Tau (HD 27397) - F0IV  
GrayGarrison89 standards: 57 Tau - F0IV [low vsini standard]
			  HD 27397 - F0IV [low vsini standard]
                          HR 8895A - F0IVn [high vsini standard]
Houk88 standard:          mu Cet - F0IV [from JM53]
GryaNstars standards:     57 Tau - F0IV

Gray06 classifies 3 stars as F0IV: HIP 9236, 72197, 84581

For Hipparcos stars within 75pc with parallax S/N > 8 (N=14):
<B-V>(F0IV) = 0.301 (+-0.009 sem, +-0.040 stdev)
<V-I>(F0IV) = 0.339 (+-0.015 sem, +-0.052 stdev)

(B-V)(F0IV) = 0.255 ; exemplar HD 95310 = 49 UMa 
(B-V)(F0IV) = 0.278 ; sec. stan. eps Cep = HD 211336
(B-V)(F0IV) = 0.288 ; pri. stan. 57 Tau = HD 27397
(B-V)(F0IV) = 0.306 ; exemplar HD 107326 = Cl Melotte 111 70
(B-V)(F0IV) = 0.306(+-0.009 sem,+-0.038 stdev) ; SIMBAD median F0IV d<75pc,V<6.5(N=25)
(B-V)(F0IV) = 0.347 ; exemplar HD 123255 = HR 5290 
(B-V)(F0IV) = 0.360 ; exemplar 23 UMa = HR 3757
=> adopt (B-V)(F0IV) = 0.30 [updated 2/2/2022]

Mv(F0IV) = -0.19 ; exemplar HD 95310 = 49 UMa
Mv(F0IV) =  1.68 ; exemplar HD 123255 = HR 5290 
Mv(F0IV) =   1.7 ; GrayCorbally09
Mv(F0IV) =  1.77 ; exemplar 23 UMa = HR 3757
Mv(F0IV) =  2.06 ; exemplar HD 107326 = Cl Melotte 111 70 (Coma Ber cluster)
Mv(F0IV) =  2.09 ; sec. stan. eps Cep = HD 211336 (~0.3 mag above MS)
Mv(F0IV) =  2.10(+-0.11 sem,+-0.53 stdev) ; SIMBAD median F0IV d<75pc,V<6.5(N=25)
Mv(F0IV) =  2.29 ; pri. stan. 57 Tau = HD 27397 (~0.2 mag above MS)
Mv(F0IV) =  2.32 ; exemplar HD 143466 = HR 5960 (near MS) 

# Primary Standard

57 Tau = HD 27397 = HR 1351 = vB 30 = VA 182 = V483 Tau = HIP 20219 (J0419+1402)
 *F0IV: MK73,Cowley74(stan),MK78,Gray89,GrayGarrison89(low-vsini stan),Gray01
  F0V: Morgan65
  
  Hyad, pmRA,pmDec = +116,-19 (TYC2), V=5.58(HIP), vsini=109 km/s.
  Delta Scuti (Rodriquez94), per=0.054 d (Samus+07). 34" binary. B-V =
  0.288+-0.0037 (Joner+06).  According to Pinsonneault04 tracks,
  B-V=0.286 (close to Joner value) corresponds to 1.72 Msun,
  Teff=7471K, and Mv=2.35. Hence the star's HRD position is consistent
  with it being on the Hyades ~0.6 Gyr MS. MK78 shows HD 27397 as the
  F0IV standard (labeled as a Hyades member), and compares it to the
  F0V standard HD 23585 (Pleiad) and F0III standard Zet Leo.  The
  Pinsonneault Hyades MS runs to 8280K (B-V=0.14; ~A3.5). Most HRD
  diagrams with luminosity tracks in B-V vs. Mv show the subgiant "IV"
  track join the upper main sequence around the early
  Fs. plx=21.9777+-0.0621mas(GaiaEDR3) => Mv=2.29, 0.19 mag above MS.

# Secondary Standard

eps Cep = HD 211336 = HR 8494 = HIP 109857 
  F0IV: JM53,Jaschek64(most),Barry70,Cowley74(stan),Ortega83,Abt95
  F0V: MK43
  F0V Sr II: Gray01
  F0: Cannon
  A9IV: GrayGarrison89
  
  B-V = 0.278, Mv=2.09, dMv= -0.33, so only slightly above MS. 
  GrayGarrison89 called "A9IV", but Gray01 called it "F0V Sr II". 
  Virtually everyone agrees on "F0" subtype. All post-JM53 consider it "IV".
  Probably an acceptable secondary standard "F0IV" a la JM53. 

# Deprecated Standard

del Aql = HR 7377 = HD 182640	
  F0IV: Slettebak55,MorganAbt72(stan),Cowley74
  F0: Bidelman85
 *F1IV-V(n): Gray01 
  F2IV-V: GrayGarrison89
  F2III: Cucchiaro78
  A9III: Abt95
  Ap: Smith71

mu Cet = HD 17094 = HR 813 (J0244+1006)
  F0IV: JM53,Jaschek64(all),Cowley74(stan),Cannon(F0) 
  F1III-IV: Malorada75
  F0III-IV: Abt95 
 *F0mF2V+: GrayGarrison89(note)
  F1IVb: Barry70
  A9IIIp: Gray03("some metals = F1")

  SB. Apparently composite. Gray/Garrison do not agree with JM53.
  GrayGarrison89 do not list it as a standard, and in the notes
  comment: "Probable composite spectrum. Close visual double with
  delta(V)=1.4 and sep=0".1."

# Exemplars 

HD 95310 = 49 UMa = HR 4288 = HIP 53838 
   F0V: 1925sdsl.book.....L, Slettebak59(F0),Cowley79(F0Vs),Sato90,Abt95
  *F0IV: Cowley76
   F0III: Bertaud67
   A7Vs: Adams35

   Decent agreement on F0-subtype, and mostly on dwarf lum class, but
   seems to be somewhat evolved - so may not be best choice of
   exemplar- so I've adopted the Cowley76 F0IV. WDS lists binary
   sep=0.4" and del(mag)=3.7 (mag1=5.10, mag2=8.80).  V=5.06(HIP),
   V=5.078+-0.008(Mermilliod91), plx=8.09+-0.66(HIP),
   plx=8.9314+-0.2104 mas (GaiaDR2). Probably reddened.
   B-V=0.255+-0.010(HIP), V-I=0.30+-0.03. WDS lists as 0.4" binary,
   del(mag) = 3.7. PASTEL: Teff=7074K(Adamczak14),
   [Fe/H]=0.11(Adamczak14), logg=3.46(Adamczak14). TIC9/Stassun19 &
   Anders18/StarHorse both list logg ~ 3. E(B-V) =
   0.006(Kervella19,STILISM) => Av = 0.020. Mv = -0.19+-0.05.

23 UMa = HR 3757 = HD 81937 = HIP 46733
   F0III:: 1919AnHar..94.....C,Cucchiaro80
   F0III-IV: Cowley76
  *F0IV: Slettebak55,GarrisonGray89
   F0V: Chalonge52,Abt95
   F0: Keenan41

   Great agreement on F0 subtype, but lum class all over the place.
   Several other F0 classifications, mostly IV and III.  V=3.65(HIP),
   B-V=0.360+-0.015(HIP), V-I=0.41+-0.03(HIP).
   plx=41.99+-0.16mas(HIP2) => Mv=1.77, 1.13 mag above the MS.

HD 107326 = Cl Melotte 111 70 = HR 4694 = HIP 60168
   A8: Stock52
   A8V: Wilson50
   A9V: Palmer68
   F0: 1938LicOB..18..167T,1953UppAn...3j...1W,1959AAHam...5..105S	
   F0V: Abt95,1963BOTT....3..137M
  *F0IV: Cowley69,GrayGarrison89,Gray01
   F0III-IV: Apenzeller67
   F0II: Duflot56
   F0/2IV/Vp: Clausen79

   Coma Ber cluster member. vsini=130km/s(Glebocki05). 
   V=6.16(HIP), B-V=0.306+-0.008(HIP), V-I=0.31+-0.03(HIP).
   plx=15.1579+-0.037mas(GaiaEDR3) => Mv=2.06, 0.51 mag above MS.

HD 123255 = HR 5290 = HIP 68940 
   A8V: Adams35
  *F0IV: Abt95,GrayGarrison89(F0IV(Cr))
   F2III: Harlan74
   F2IV: Cowley74

   V=5.46(HIP), B-V=0.347+-0.005(HIP), V-I=0.41+-0.02(HIP).
   plx=17.5627+-0.0994mas(GaiaEDR3) => Mv=1.68, 1.14 mag above
   MS.

HD 208450 = del Ind = HR 8368
   A8(V)+F3(V): Beavers80
   F0III: Cucchiaro78
   F0III-IVn: GrayGarrison89
  *F0IV: deVaucouleurs57,Evans64,Malaroda75,Houk75,Abt95
   F0V: 1937AnHar.105...45H, 1955MmMtS..12....1W

   0.1" binary in HIP/CCDM, Hp(A)=4.799, Hp(B)=5.959 =>
   delta(Hp)=1.16.  V(AB)=4.40(HIP), B-V=0.297+-0.013(HIP),
   V-I=0.35+-0.02(HIP).  Adopting del(V) = 1.16 from del(Hp) & V=4.40
   => V(A)=4.72, V(B)=5.88. plx=17.34+-0.48mas(HIP2) => Mv(A)=0.92,
   Mv(B)=2.08.
   

# Other Stars


alf Hyi = HD 12311 = HR 591 
   A7n: 1932PLicO..18....1M
   A9III:  1957MNRAS.117..449D
   F0III-IVn: GrayGarrison89
  *F0IV: Abt95,Gray06
   F0V: 1937AnHar.105...45H,Woods55,Houk75(Garrison)

   Several F0 classifications, recently IV.

51 Eri = HR 1474 
   A7V: Maury1897
  *F0IV: GarrisonGray89,Abt95
   F0V: Cowley69
   F2IV: Davis67

   Famous host star to directly imaged young planet 51 Eri b.  Beta
   Pic MG member so ~20 Myr.  Two distant M dwarf companions GJ 3305.

HD 905 = HR 41 = HIP 1086 
   F0IV: Cowley69, Abt95(F0IVs)
   A7: 1932PLicO..18....1M

HD 37788 = HR 1955 = HIP 26762
   A7V: Palmer68
   F0V+: GrayGarrison89
  *F0IVs: Abt95
   F0IV: Cowley69

HD 55892 = HR 2740
   F0IV: Malaroda75,Houk78,GrayGarrison89(G0IVs)
   F1V: 1937AnHar.105...45H
   F2III: Cucchiaro78
   F3V_Fe-1.0: Gray06

HD 69682 = HR 3258 = HIP 40878
  *F0V: Cowley74
   F0IV: Cowley65,Abt95
   F0III: Grenier99
   Fm delta Del: 1966VA......8...53B

   HRD suggests this is really a main sequence star.  V=6.50(HIP),
   B-V=0.300+-0.007(HIP), V-I=0.34+-0.01(HIP).
   plx=16.5406+-0.0268mas(GaiaEDR3) => Mv=2.59 (0.05 mag below MS).

HD 143466 = HR 5960 = HIP 78180 
  *F0IV: Slettebak55,Cowley69,GrayGarrison89
   F0V: Abt95
   F1IVab: Barry70(uv metals weak)
 
   Mostly classified as subgiant but HRD position seems like middle of
   main sequence.  V=4.96(HIP), B-V=0.269+-0.008(HIP),
   V-I=0.29+-0.03(HIP) plx=29.6204+-0.0809mas(GaiaEDR3) => Mv=2.32 =>
   0.05 mag above MS.

HD 163929
   F0V: Sato90
  *F0IV: Cowley74,Grenier99
   F2III: Cowley79

del Ser B = HD 138917
   F0V: Adams35
   F0IV-V: Slettebak63
   F0IV: Abt95
   F0IIIb: GrayGarrison89
   F0: 	1923LicOB..10..169L

   Great agreement on subtype, awful agreement on luminosity class. 



# COMMENTS ON COLORS OF F SUBGIANTS

Using the Hipparcos catalog, I selected 127 F subgiants which 
had d<75 pc and plx S/N>8. No stars with slash or dashed types were included.
For these 127 F subgiants, the B-V colors were compared to the mean
B-V colors for F dwarfs of the same temperature type. I find:

<(B-V)FIV> - <(B-V)FV> = 0.000 +- 0.004 (stdev = 0.038 mag; N=127). 

Hence, for a given subtype, F subgiants have the same mean color as F
dwarfs of the same temperature type (to <0.01 mag).

For the individual subtypes:
<(B-V)F0IV> - <(B-V)F0V> =  0.012+-0.008 (stdev = 0.047 mag; N=32)
<(B-V)F1IV> - <(B-V)F1V> =  0.026+-0.014 (stdev = 0.030 mag; N=6)
<(B-V)F2IV> - <(B-V)F2V> = -0.005+-0.006 (stdev = 0.025 mag; N=16)
<(B-V)F3IV> - <(B-V)F3V> =  0.002+-0.010 (stdev = 0.038 mag; N=14)
<(B-V)F4IV> - <(B-V)F4V> =  0.017+-0.027 (stdev = 0.046 mag; N=14)
<(B-V)F5IV> - <(B-V)F5V> = -0.015+-0.013 (stdev = 0.034 mag; N=20)
<(B-V)F6IV> - <(B-V)F6V> = -0.015+-0.009 (stdev = 0.035 mag; N=19)
<(B-V)F7IV> - <(B-V)F7V> = -0.007+-0.021 (stdev = 0.051 mag; N=7)
<(B-V)F8IV> - <(B-V)F8V> =  0.006+-0.011 (stdev = 0.028 mag; N=10)

#B-V   SpT (B-V)_V (B-V)-(B-V)_V
0.331  F0  0.294  0.037
0.259  F0  0.294  -0.035
0.349  F0  0.294  0.055
0.347  F0  0.294  0.053
0.325  F0  0.294  0.031
0.483  F0  0.294  0.189
0.401  F0  0.294  0.107
0.322  F0  0.294  0.028
0.311  F0  0.294  0.017
0.375  F0  0.294  0.081
0.324  F0  0.294  0.03
0.320  F0  0.294  0.026
0.300  F0  0.294  0.006
0.209  F0  0.294  -0.085
0.244  F0  0.294  -0.05
0.306  F0  0.294  0.012
0.309  F0  0.294  0.015
0.277  F0  0.294  -0.017
0.241  F0  0.294  -0.053
0.352  F0  0.294  0.058
0.269  F0  0.294  -0.025
0.289  F0  0.294  -0.005
0.273  F0  0.294  -0.021
0.326  F0  0.294  0.032
0.216  F0  0.294  -0.078
0.229  F0  0.294  -0.065
0.316  F0  0.294  0.022
0.319  F0  0.294  0.025
0.308  F0  0.294  0.014
0.357  F0  0.294  0.063
0.278  F0  0.294  -0.016
0.300  F0  0.294  0.006
0.338  F1  0.334  0.004
0.381  F1  0.334  0.047
0.361  F1  0.334  0.027
0.361  F1  0.334  0.027
0.393  F1  0.334  0.059
0.314  F1  0.334  -0.02
0.386  F2  0.374  0.012
0.307  F2  0.374  -0.067
0.395  F2  0.374  0.021
0.345  F2  0.374  -0.029
0.466  F2  0.374  0.092
0.358  F2  0.374  -0.016
0.369  F2  0.374  -0.005
0.371  F2  0.374  -0.003
0.375  F2  0.374  0.001
0.369  F2  0.374  -0.005
0.363  F2  0.374  -0.011
0.406  F2  0.374  0.032
0.376  F2  0.374  0.002
0.391  F2  0.374  0.017
0.336  F2  0.374  -0.038
0.344  F2  0.374  -0.03
0.292  F3  0.389  -0.097
0.332  F3  0.389  -0.057
0.402  F3  0.389  0.013
0.345  F3  0.389  -0.044
0.377  F3  0.389  -0.012
0.440  F3  0.389  0.051
0.415  F3  0.389  0.026
0.415  F3  0.389  0.026
0.429  F3  0.389  0.04
0.412  F3  0.389  0.023
0.386  F3  0.389  -0.003
0.378  F3  0.389  -0.011
0.394  F3  0.389  0.005
0.386  F3  0.389  -0.003
0.428  F4  0.412  0.016
0.383  F4  0.412  -0.029
0.475  F4  0.412  0.063
0.453  F5  0.438  0.015
0.398  F5  0.438  -0.04
0.421  F5  0.438  -0.017
0.415  F5  0.438  -0.023
0.425  F5  0.438  -0.013
0.393  F5  0.438  -0.045
0.401  F5  0.438  -0.037
0.384  F5  0.438  -0.054
0.461  F5  0.438  0.023
0.438  F5  0.438  0
0.385  F5  0.438  -0.053
0.401  F5  0.438  -0.037
0.443  F5  0.438  0.005
0.442  F5  0.438  0.004
0.394  F5  0.438  -0.044
0.474  F5  0.438  0.036
0.459  F5  0.438  0.021
0.450  F5  0.438  0.012
0.378  F5  0.438  -0.06
0.450  F5  0.438  0.012
0.470  F6  0.484  -0.014
0.555  F6  0.484  0.071
0.412  F6  0.484  -0.072
0.497  F6  0.484  0.013
0.452  F6  0.484  -0.032
0.471  F6  0.484  -0.013
0.454  F6  0.484  -0.03
0.444  F6  0.484  -0.04
0.480  F6  0.484  -0.004
0.455  F6  0.484  -0.029
0.449  F6  0.484  -0.035
0.526  F6  0.484  0.042
0.505  F6  0.484  0.021
0.458  F6  0.484  -0.026
0.414  F6  0.484  -0.07
0.443  F6  0.484  -0.041
0.490  F6  0.484  0.006
0.529  F6  0.484  0.045
0.465  F6  0.484  -0.019
0.576  F7  0.510  0.066
0.571  F7  0.510  0.061
0.510  F7  0.510  0
0.478  F7  0.510  -0.032
0.489  F7  0.510  -0.021
0.476  F7  0.510  -0.034
0.487  F7  0.510  -0.023
0.504  F8  0.530  -0.026
0.537  F8  0.530  0.007
0.554  F8  0.530  0.024
0.570  F8  0.530  0.04
0.523  F8  0.530  -0.007
0.553  F8  0.530  0.023
0.513  F8  0.530  -0.017
0.529  F8  0.530  -0.001
0.517  F8  0.530  -0.013
0.572  F8  0.530  0.042