M1.5V

Kirkpatrick(in GrayCorbally09) call Gl 205 the M1.5V primary standard. This
is agreement among many sources (Keenan, Kirkpatrick, Hawley, Reid, Houk) as
a M1.5V.

Both the primary and secondary standards appear to be metal-rich, with
radii larger and absolute magnitudes tenths of a magnitude brighter
than average for the type.

KeenanMcNeil76 standard:        GJ 49 - M1.5V
Keenan80 standard:              GJ 205 (=HD 36395) - M1.5V
Keenan83 standard:              GJ 205 (=HD 36395) - M1.5V
	                        GJ 570B (=HD 131976) - M1.5V
Turnshek85 standard:            GJ 205 (=HD 36395) - dM1.5
Keenan85 standard:              GJ 205 (=HD 36395) - M1.5V
Corbally86 standard:            GJ 205 (=HD 36395) - M1.5V 
Keenan88 standard:              GJ 205 (= HD36395) - M1.5V
                                GJ 570B - M1.5V
Keenan89 standard:              GJ 205 (= HD 36395) - M1.5V
                                GJ 570B (=HD 131976) - M1.5V
Kirkpatrick91 standard:         GJ 205 (=HD 36395) - M1.5V
Henry02 standards:              GJ 15A - M1.5V (from Henry94)
				GJ 205 - M1.5V (from Kirkpatrick91)
				GJ 526 - M1.5V (from Henry94)
				GJ 625 - M1.5V (from Henry94)
				GJ 880 - M1.5V (from Henry94)
GrayAtlas standard:             BD+43_44A - M1.5V
GrayNstars standard:            GJ 570B (=HD 131976) - M1.5V
Kirkpatrick(in GrayCorbally09): GJ 205 - M1.5V
	       			GJ 570B - M1.5V

Joy74 M1.5V stars appear to be approximately M1-V (~M0.75+-1 subtype)
on the Kirkpatrick91 system.

(B-V)(M1.5V)  =  1.415 ; exemplar GJ 366 = Ross 434 
(B-V)(M1.5V)  =   1.448; deprecated stan. GJ 526
(B-V)(M1.5V)  =  1.464 ; exemplar GJ 908 = LHS 550 
(B-V)(M1.5V)  = 1.474  ; pri. stan. GJ 205 (Landolt83)
(B-V)(M1V)    = 1.485  ; adopted
(B-V)(M2V)    = 1.505  ; adopted
(B-V)(M1.5V)  = 1.505  ; Koen10 d<25pc median M1.5V
(B-V)(M1.5V)  = 1.512  ; sec. stan. GJ 880 (Mermilliod91)
(B-V)(M1.5V)  =   1.567; deprecated stan. GJ 15A
(B-V)(M1.5V)  =   1.603; deprecated stan. GJ 625
=> adopt (B-V)(M1.5V) = 1.495 [updated 8/13/2020]

(V-I)(M1.5V)  = 2.15  ; Hawley96
(V-I)(M1.5V)  = 2.076 ; pri. stan. GJ 205 (Landolt83)

<V-J>(M1.5V)  = 3.36 (+-0.23 stdev) ; Lepine12

(V-Ks)(M1.5V) =  4.278 ; depreciated stan. GJ 625
(V-Ks)(M1.5V) = 4.156 ; pri. stan. GJ 205 (estimated from V-R color)
(V-K)(M1.5V)  =  4.15  ; Hawley96
(V-Ks)(M1.5V) = 4.149 ; sec. stan. GJ 880
(V-Ks)(M1.5V) = 4.116 ; exemplar GJ 134 = HD 275122 
(V-Ks)(M1.5V) = 4.104 ; pri. stan. GJ 205 (from synthetic Ks mag from Mann15)
(V-Ks)(M1.5V) = 4.102 ; pri. stan. GJ 205 (estimated from V-I color)
(V-Ks)(M1.5V) = 4.079 ; trend K/M dwarfs for standards & exemplars
(V-Ks)(M1.5V) = 4.045 ; ter. stan. GJ 526
(V-Ks)(M1.5V) = 4.014 ; pri. stan. GJ 205 (estimated from B-V color)
(V-Ks)(M1.5V) = 3.986 ; exemplar GJ 366 = Ross 434 
(V-Ks)(M1.5V) = 3.940 ; exemplar GJ 908 = LHS 550 
=> adopt (V-Ks)(M1.5V) = 4.10   [last updated 11/1/2019]
=> adopt (U-B)(M1.5V)  = 1.171
=> adopt (B-V)(M1.5V)  = 1.484 
=> adopt (V-I)(M1.5V)  = 2.075
=> adopt (V-R)(M1.5V)  = 0.974
=> adopt (R-I)(M1.5V)  = 1.101
=> adopt (V-J)(M1.5V)  = 3.265
=> adopt (V-H)(M1.5V)  = 3.873
=> adopt (H-Ks)(M1.5V) = 0.227
=> adopt (J-H)(M1.5V)  = 0.608
=> adopt (I-Ks)(M1.5V) = 2.031**fix 
=> adopt (K-W1)(M1.5V) = 0.140

(G-J)(M1.5V)   = 2.312 ; Bentley18/interp
(G-Ks)(M1.5V)  = 3.162 ; Bentley18/interp
(Ks-W2)(M1.5V) = 0.226 ; Bentley18/interp
(W1-W2)(M1.5V) = 0.080 ; Bentley18/interp

(Ks-W1)(M1.5V) = 0.147 ; Bentley18/interp
(Ks-W1)(M1.5V) = 0.140 ; fit to Winters15 data for V-Ks=4.10
(Ks-W1)(M1.5V) = 0.110 ; Best18 
(Ks-W1)(M1.5V) = 0.099 ; Avenhaus12 for V-Ks=4.10
=> adopt (Ks-W1)(M1.5V) = 0.135 [updated 12/29/2019]

(Bp-Rp)(M1.5V) = 2.1050 ; GJ_908      exemplar
(Bp-Rp)(M1.5V) = 2.1161 ; GJ_366      exemplar 
(Bp-Rp)(M1.5V) = 2.1174 ; BD+18_3421  
(Bp-Rp)(M1.5V) = 2.1130 ; GJ_526      ter. stan.
(Bp-Rp)(M1.5V) = 2.1254 ; GJ_134      exemplar 
(Bp-Rp)(M1.5V) = 2.1257 ; GJ_205      pri. stna.
(Bp-Rp)(M1.5V) = 2.1553 ; GJ_880      sec. stan.
(Bp-Rp)(M1.5V) = 2.1649 ; MCC_135     
(Bp-Rp)(M1.5V) = 2.1731 ; V*_GX_And   
(Bp-Rp)(M1.5V) = 2.1805 ; BD+61_195   
(Bp-Rp)(M1.5V) = 2.2773 ; CD-48_11837
(Bp-Rp)(M1.5V)=  2.3002 ; G_202-48_   
(Bp-Rp)(M1.5V) = 2.3033 ; HD_156384C  
=> adopt (Bp-Rp)(M1.5V) = 2.13 [updated 11/18/2020]

(G-Rp)(M1.5V) =  1.0108 ; GJ_366       exemplar 
(G-Rp)(M1.5V) =  1.0148 ; GJ_134       exemplar 
(G-Rp)(M1.5V) =  1.0165 ; BD+18_3421   M1.5V
(G-Rp)(M1.5V) =  1.0170 ; GJ_809       exemplar 
(G-Rp)(M1.5V) = 1.0174 ; GJ_205       pri. stan.
(G-Rp)(M1.5V) = 1.0205 ; GJ_526       ter. stan.
(G-Rp)(M1.5V) =  1.0278 ; MCC_135      M1.5V
(G-Rp)(M1.5V) = 1.0291 ; GJ_880       sec. stan. 
(G-Rp)(M1.5V) =  1.0309 ; BD+61_195    M1.5V
(G-Rp)(M1.5V) = 1.033  ; color trend M0V-M9V 
(G-Rp)(M1.5V) =  1.0340 ; V*_GX_And    M1.5V
(G-Rp)(M1.5V) =  1.0643 ; CD-48_11837  M1.5V
(G-Rp)(M1.5V)=   1.0679 ; G_202-48_    M1.5V
(G-Rp)(M1.5V) =  1.0690 ; HD_156384C   M1.5V
=> adopt (G-Rp)(M1.5V) = 1.02 [updated 11/18/2020]
=> adopt (Bp-G)(M1.5V) = 1.11 [updated 11/18/2020; Bp-Rp=2.13,  G-Rp=1.02]

(Bp-G)(M1.5V) = 1.0925 ; GJ_526
(Bp-G)(M1.5V) = 1.1084 ; GJ_205 
(Bp-G)(M1.5V) = 1.1262 ; GJ_880

(G-V)(M1.5V) = -0.872  ; polynomial fit to SIMBAD d<25pc M dwarfs
(G-V)(M1.5V) = -0.8695 ; GJ_205
(G-V)(M1.5V) = -0.867  ; trend Kervella19 d<25pc sample for V-Ks=4.10
(G-V)(M1.5V) = -0.8532 ; GJ_526  
(G-V)(M1.5V) = -0.8449 ; GJ_880
=> adopt (G-V)(M1.5V)  = -0.87 [updated 11/1/2020]
=> adopt (G-Ks)(M1.5V) = 4.10 + -0.87 = 3.23 [updated 11/1/2020]

(r-i)(M1.5V) = 0.856 (+-0.05 rms) ; West05 fit for (V-Ic)=2.075

(z-J)(M1.5V) = 1.361 (+-0.028 rms) ; poly fit to d<100pc GCNS for G-Ks=3.23


Teff(M1.5V) =  3533 K ; Morrell19 <Teff> for stars w/i +-0.05 mag of M_Ks=5.82
Teff(M1.5V) =   3535 +- 14 K ; Pecaut13 (deprecated stan. GJ 15A)
Teff(M1.5V) =  3564 +- 44 K ; Lepine12
Teff(M1.5V) =   3563 +- 11 K ; deprecated standard GJ 15A (Boyajian12)
Teff(M1.5V) =   3596 +- 25 K ; Pecaut13 (GJ 880)
Teff(M1.5V) =  3600 K ; Rajpurohit13 (N=2; LHS 14A, LHS 65A)
Teff(M1.5V) = 3620 K ; Rad=0.482Rsun for Mann15 calib for M_Ks=5.75, [Fe/H]=0.0
Teff(M1.5V) =  3640 K ; empirical L-R relation, logL=-1.444
Teff(M1.5V) =  3650 K ; ter. stan. GJ 526
Teff(M1.5V) =  3674 +- 10 K ; Boyajian12b (N=4)
Teff(M1.5V) =  3677 K ; Passegger18 median Teff for CARMENES M1.5V(N=23)
Teff(M1.5V) =  3683 K ; smooth Teff(SpT) trend
Teff(M1.5V) =   3703 +- 36 K ; Pecaut13 (GJ 205)
Teff(M1.5V) =  3750 K ; sec. stan. GJ 880 (median Teff, but metal-rich)
Teff(M1.5V) =  3760 K ; pri. stan. GJ 205 (median Teff, but metal-rich)
=> adopt Teff(M1.5V) = 3620 K (logT = 3.559) [updated 8/13/2020]

BCv(M1.5V) = -1.529 +- 0.022 ; deprecated standard GJ 15A (Pecaut13)
BCv(M1.5V) = -1.523 +- 0.019 ; pri. stan. GJ 205 (Pecaut13)
BCv(M1.5V) = -1.50           ; BC_Ks=2.60, V-Ks=4.10
BCv(M1.5V) = -1.494 +- 0.024 ; sec. stan. GJ 880 (Pecaut13)
BCv(M1.5V) = -1.432 +- 0.019 ; non-standard GJ 526 (Pecaut13)
=> adopt BCv(M1.5V) = -1.50 [updated 11/3/2019; BC_K=2.60, V-K=4.10]

BC_K(M1.5V) = 2.541 ; smoothed trend over M0V-M9V for M1V
BC_Ks(M1.5V)= 2.596 ; Mann15 for V-J=3.265
BC_Ks(M1.5V)= 2.603 ; Morrell19 trend for G-Ks=3.27
BC_K(M1.5V) = 2.613 +- 0.021 ; non-stan GJ 526 (Pecaut13) 
BC_K(M1.5V) = 2.655 +- 0.026 ; sec. stan. GJ 880 (Pecaut13)
=> adopt BC_K(M1.5V) = 2.60 [updated 11/3/2019]

Mv(M1.5V) =   9.14 ; Kirkpatrick94
Mv(M1.5V) =  9.19 ; pri. stan. GJ 205 (metal-rich)
Mv(M1.5V) =  9.26 ; exemplar GJ 134 = HD 275122 
Mv(M1.5V) =  9.49 ; sec. stan. GJ 880 = HD 216899 (metal-rich)
Mv(M1.5V) =  9.62 ; exemplar GJ 366 = Ross 434 
Mv(M1.5V) =  9.78 ; EEM fit to Jao16 data for V-Ks=4.10
Mv(M1.5V) = 9.85 ; M_Ks=5.75, V-Ks=4.10
Mv(M1.5V) =  9.86 ; Koen10 d<25pc median for M1.5V
Mv(M1.5V) =  9.89 ; Finch14 calibration for V-Ks=4.10
Mv(M1.5V) =  9.91 ; JohnsonApps09 calibration for V-Ks=4.10
Mv(M1.5V) =  9.94 ; Dieterich14 calibration for V-Ks=4.12
Mv(M1.5V) =  10.02 ; Henry04 calibration for V-Ks=4.10
Mv(M1.5V) =  11.05 ; deprecated stan. GJ 625
=> adopt Mv(M1.5V)   = 9.85 [updated 12/10/2020] (M_Ks=5.75, V-Ks=4.10)
=> adopt M_G(M1.5V)  = 8.98 [updated 12/10/2020] (Mv=9.85, G-V=-0.87)
=> adopt M_Ks(M1.5V) = 5.75 [updated 12/10/2020] (Mv=9.85, V-Ks=4.10)

M_G(M1.5V) =   8.31848 ; HD 131976                    
M_G(M1.5V) =   8.31952 ; HD 36395                     
M_G(M1.5V) =   8.53075 ; BD+57 2735                  
M_G(M1.5V) =   8.60896 ; HD 216899                    
M_G(M1.5V) =   8.69469 ; BD+61 195                    
M_G(M1.5V) =  8.83694 ; HD 318327                   
M_G(M1.5V) =  8.89001 ; * tet Per B
M_G(M1.5V) = 8.983   ; Mv=9.85, G-V=-0.877
M_G(M1.5V) =  8.993   ; SIMBAD d<20pc trend for V-Ks=4.10
M_G(M1.5V) =  9.004   ; trend d<10pc SIMBAD
M_G(M1.5V) =  9.02662 ; CD-36 2458                  
M_G(M1.5V) =  9.0712  ; HD 154363B                    
M_G(M1.5V) =  9.13619 ; MCC 135                      
M_G(M1.5V) =  9.18074 ; BD+18 3421                   
M_G(M1.5V) =  9.19005 ; CD-53 570                   
M_G(M1.5V) =  9.28757 ; G 125-30                    
M_G(M1.5V) =   10.0797  ; HD 156384C                   
M_G(M1.5V) =   10.0812  ; G 202-48

M_Ks(M1.5V) =  5.82 ; Dieterich14 calibration for V-Ks=4.12
M_Ks(M1.5V) =  5.82 ; EEM calib for Winters15 data for V-Ks=4.12
M_Ks(M1.5V) =  5.81 ; JohnsonApps09 calibration for V-Ks=4.10
M_Ks(M1.5V) =  5.79 ; Finch14 calibration for V-Ks=4.10
M_Ks(M1.5V) = 5.75 ; Mv=9.85, V-Ks=4.10
M_Ks(M1.5V) =  5.68 ; Jao16 calibration for V-Ks=4.10
M_Ks(M1.5V) =  5.64 ; exemplar GJ 366 = Ross 434 
M_Ks(M1.5V) =  5.34 ; sec. stan. GJ 880 = HD 216899 
M_Ks(M1.5V) =  5.15 ; exemplar GJ 134 = HD 275122 

logL(M1.5V) = -1.473 ; Morrell19 trend for logL for M_Ks=5.82
logL(M1.5V) = -1.444 ; M_Ks=5.75, BC_Ks=2.60, MBbol = 8.35
=> adopt logL(M1.5V) = -1.444 [updated 8/13/2020]
=> adopt Mbol(M1.5V) =  8.350 [updated 8/13/2020]

Rad(M1.5V) = 0.566+-0.002   Rsun ; pri. stan. GJ 205 = HD 36395 (Rabus19) [metal rich]
Rad(M1.5V) = 0.574+-0.004   Rsun ; pri. stan. GJ 205 = HD 36395 (Yee17) [metal rich]
Rad(M1.5V) = 0.549          Rsun ; sec. stan. GJ 880 = HD 216899 [metal-rich]
Rad(M1.5V) = 0.548+-0.005   Rsun ; sec. stan. GJ 880 = HD 216899 (Yee17) [metal-rich]
Rad(M1.5V) = 0.4979+-0.0026 Rsun ; Boyajian12b (N=4)
Rad(M1.5V) = 0.483          Rsun ; Rabus19 trend for Teff=3640K
Rad(M1.5V) = 0.482          Rsun ; Mann15 trend M_Ks=5.75, [Fe/H]=0.0
Rad(M1.5V) = 0.482          Rsun ; logL=-1.444, Teff=3620K
Rad(M1.5V) = 0.3874+-0.0023 Rsun ; deprecated standard GJ 15A (Boyajian12)
=> adopt Rad(M1.5V) = 0.482 Rsun [updated 8/13/2020]

Mass(M1.5V) =  0.405+-0.008 Msun ; pri. of GJ22AC, unresolved SpT=M1.5V (Benedict16)
Mass(M1.5V) = 0.474  Msun ; Benedict16 calib. for Mv=9.85
Mass(M1.5V) = 0.4785 Msun ; Mann18 calib. for M_Ks=5.75
Mass(M1.5V) =  0.511 Msun ; Delfosse00 calib for Mv=9.85
Mass(M1.5V) =  0.500 Msun ; Delfosse00 calib. for M_Ks=5.75
Mass(M1.5V) = 0.540  Msun ; Benedict16 calib. for M_Ks=5.75
Mass(M1.5V) =  0.586+-0.007 Msun ; GJ570B (Benedict16)
Mass(M1.5V) =  0.600+-0.006 Msun ; GU Boo B (Benedict16)
Mass(M1.5V) =  0.615 Msun ; Torres10 calib. for Mv=9.85
=> adopt Mass(M1.5V) = 0.48 Msun [updated 8/13/2020]

# No Standard
Boeshaar85 does not list an M1.5V standard.

# Primary Standard

GJ 205 = HD 36395 = LHS 30
  M1V: JM53(non-stan.,"dM1")
 *M1.5Ve: Boeshaar76,KeenanMcNeil76(stan),Keenan85,Corbally86(stan,Keenan80),Keenan88,Kirkpatrick91(pri),Hawley97,Keenan99,Houk99,Henry02,Reid04,Mann15
  M2.33: Terrien15

  Excellent recent agreement on type, and has interferometric diameter
  and Teff estimates. Appears to be metal-rich [Fe/H] ~
  +0.4. Segransan03 VLTI study reports: M = 0.631+-0.031 Msun,
  R=0.702+-0.063 Rsun, Teff = 3520+-170 K, logg=4.54+-0.06
  dex. KeenanMcNeil76 do not list Gl 205 as a standard in their Table
  3, however they do show it as a M2 dwarf in their Plate
  19. V=7.966+-0.011(Mermilliod91), V=7.960(Landolt83),
  B-V=1.474+-0.009(Mermilliod91), B-V=1.474(Landolt83),
  U-B=1.213+-0.024(Mermilliod91), U-B=1.231(Landolt83),
  V-R=0.985(Landolt83), R-I=1.095(Landolt83), V-I=2.076(Landolt83).
  Unfortunately all 2MASS photometry is saturated, but Mann15 fits
  synthetic 2MASS magnitudes: J=4.796+-0.017, H=4.123+-0.017,
  Ks=3.856+-0.019. Teffs: 3520+-170K(Segransan03),
  3708K(Prugniel07#2), 3719K(Prugniel07#1), 3732+-56K(Ramirez05),
  3737K(Alonso96), 3760K(Wolff05), 3801+-60K(Mann15),
  3835+-69K(Rabus19), 3850+-22K(Newton15#1), 3872K(Newton15#2),
  4012+-106K(Rojas-Ayala12) => <Teff> = 3760K.
  R=0.5735+-0.044Rsun(Newton14), R=0.581+-0.019Rsun(Mann15),
  logL=-1.1905+-0.0094(Newton14), M=0.633+-0.063Msun(Mann15),
  [Fe/H]=0.49+-0.08(Mann15). plx=175.4287+-0.0672mas(GaiaDR2).
  Mv=9.19+-0.01(Mermilliod91,GaiaDR2). Boyajian12 reports
  tetLD=0.943+-0.004mas. Boyajian12+GaiaDR2 => Rad = 0.578Rsun.
  Rabus19: tetLD=0.924+-0.003mas, fbol=(6.140+-0.400)e-8,
  Rad=0.566+-0.002Rsun, Teff=3835+-69K.  [Fe/H] =
  0.35+-0.17(RoyasAyala12), 0.43+-0.08(Gaidos14), 0.69(Terrien15,
  seems too high!), 0.49+-0.08(Mann15).

# Secondary Standard

GJ 880 = HD 216899 = BD+15_4733 = Ross 671
   M1.43: Terrien15(epoch#1)
  *M1.5V: Henry94,Hawley97,Henry02(stan),Reid04,Kirkpatrick12(KirkpatrickPhD),Lepine13,Mann15
   M1.78: Terrien15(epoch#2)
   M2: Vyssotsky56,Bidelman85
   M2.5V: Joy74
   
   V=8.672+-0.013(Mermilliod91), V=8.66(Weis93),
   B-V=1.512+-0.006(Mermilliod91), B-V=1.50(Weis93), V-R=1.06(Weis93),
   R-I=0.87(Weis93), U-B=1.175+-0.010(Mermilliod91),
   J=5.360+-0.020(2MASS), Ks=4.523+-0.016(2MASS),
   V-Ks=8.672-4.523=4.149+-0.021(Mermilliod91,2MASS). 2MASS H-band is
   flagged 'E'.  mbol=7.178+-0.020(Pecaut13). BC_Ks = mbol - Ks =
   7.178 - 4.523 = 2.655+-0.026.  BCv = mbol - V = 7.178 - 8.672 =
   -1.494+-0.024.  Teff = 3520K(Lepine13), 3720+-60K(Mann15#1),
   3731+-16K(Newton15#2), 3749+-76K(Newton15#2), 3759K(Alonso96),
   3760+-35K(Mann15#2), 3808+-70K(Ramirez05) => <Teff>=3750K.
   R=0.5490+-0.0180Rsun(Mann15), R=0.5477+-0.0048Rsun(Newton15),
   R=0.548+-0.005Rsun(Therrien15), M=0.5740+-0.0570Msun(Mann15),
   [Fe/H]=0.21+-0.08 (more Mann15 numbers),
   logL=-1.2856+-0.0049(Newton15). Boyajian12 reports
   tetLD=0.744+-0.004mas.
   plx=145.6107+-0.0388mas(GaiaDR2). Boyajian12+GaiaDR2 => Rad
   =0.549Rsun. Rad=0.548+-0.005Rsun(Yee17).  Metallicities are all
   over the place, but the star has a large radius and is probably
   metal-rich, as some recent results have been indicating - probably
   [Fe/H] ~ +0.1.: [Fe/H]= -1.50(Alonso96), -0.01+-0.09(Maldonado19),
   +0.026+-0.080(Hojjatpanah19), +0.06+-0.10(Yee17), +0.07(Neves13),
   +0.12+-0.16(Schweitzer19), +0.18+-0.11(Gaidos14),
   +0.20+-0.05(Lindgren17). Mv=9.488+-0.013(Mermilliod91,GaiaDR2),
   M_Ks=5.339+-0.016(2MASS,GaiaDR2).

# Tertiary Standard

GJ 526 = HD 119850 = StKM 2-980 = LHS 47
  M1: Gaidos14
  M1.4: Mann15
 *M1.5V: Bidelman85(M1.5),Henry94,Hawley97,Henry02(stan)
  M2V: Keenan85,Keenan88,Keenan89,GrayNstars,Newton14(near-IR)
  M3V: Joy74,Stephenson86

  Reasonable agreement between Henry, Hawley, and Mann, although
  notably Keenan and Newton place the type 0.5 later.  Colors and
  Teffs consistent with the other M1.5V standards.
  (B-V)=1.448+-0.017(Mermilliod91), V=8.460+-0.014(Mermilliod91),
  (U-B)=1.099+-0.023(Mermilliod91). 2MASS photometry, only K band is
  flagged as A quality: Ks=4.415+-0.017(2MASS). V-Ks = 8.460 - 4.415 =
  4.045. mbol=7.028+-0.013(Pecaut13).  BC_Ks = mbol - Ks = 7.028 -
  4.415 = 2.613+-0.021. Teffs: 3570+-16K(Pecaut13), 3618K(Boyajian12),
  3623K(Prugniel07), 3646+-34K(Newton14), 3650K(Woolf05),
  3664+-153K(vanBelle09), 3680K(Prugniel07#2), 3716+-125K(Newton14#2),
  3792+-92K(Gaidos14) => <Teff> = 3650K. [Fe/H]=-0.31+-0.08(Mann15),
  -0.18+-0.09(Gaidos14), [Fe/H]=-0.10, -0.33(Prugniel07, 2 values),
  [Fe/H] = -0.10+-0.07(Woolf05).  Star is apparently somewhat metal
  poor.

# Deprecated Standards

GJ 15A = BD+43_44A = GX And = HD 1326A
  M1V: JM53(non-standard),Hawley97,Reid04
 *M1.5V: GrayAtlas,Boeshaar94,Kirkpatrick94,Henry94(not standard),Henry02
  M2V: Keenan85,Keenan88,Keenan99,Sozetti02

  Keenan repeatedly classified GJ 15A as M2, but everyone else
  considers it M1 or M1.5. V=8.089+-0.017(Mermilliod91),
  B-V=1.567+-0.014(Mermilliod91),
  U-B=1.222+-0.026(Mermilliod91). Segranson03 VLTI study:
  M=0.414+-0.021 Msun, R=0.383+-0.02 Rsun, Teff = 3698+-95 K,
  logg=4.89+-0.06 dex.  fbol = (5.420+-0.044)e-8 erg/cm/s^2
  (Boyajian12), L = 0.02173+-0.00021 Lsun (Boyajian12), Teff=3563+-11
  K (Boyajian12), R = 0.3874+-0.0023 Rsun (Boyajian12). [Fe/H]=-0.36
  (Neves11). 2MASS photometry poor. 

GJ 570B = HD 131976
  M1.5V: Keenan85,Keenan88,GrayNstars
 *M1.0VJ: Henry02

GJ 570BC = LHS 386 = HD 131976 = BD-20 4123 = Lalande 27173BC
  M0.5: Bidelman85
  M1.0V: Walker83,Henry94(Kirkpatrick12),Hawley97,Henry02("joint"),Geballe02,Houdebine12(dM1)
 *M1V+M3:V: Kirkpatrick12
  M1.0V+M1.0V: Reid04
  M1.5V: Keenan85,Keenan89(stan),Gray06
  M1.5V+M3V: Pourbaix/SB9
  M2V: Vyssotsky56,Cowley67,Joy74,Stephenson86,Gaidos14,Newton14
  M2III: Houdebine10(prob. because of poor parallax)

  Unfortunately Keenan considered M1.5, but Henry considers M1. I
  deprecate the Keenan type as the Henry types have become modern
  standards. 0.0437" binary according to Tokovinin15, with
  delta(y)=1.6, and SB orbit from Forvielle99 (Period 308 days).  25"
  away from primary HR 5568 (HD 131977). Forveille99 splits the BC
  components, with M_J(B) = 6.213+-0.033, M_J(C) = 7.403+-0.039, and
  M_K(B) = 5.396+-0.033, M_K(C) = 6.576+-0.039, so delta(K) =
  1.18. Given this delta(mag), it likely that the companion is >2
  subtypes later, similar to what Pourbaix reports. Forvielle99
  section 4 discusses the IR photometry for the pair in more
  detail. Magnitudes are unresolved unless specifically stated:
  V=8.065(Koen10), B-V=1.494(Koen10), U-B=1.200(Koen10),
  V-Rc=0.990(Koen10), V-Ic=2.122(Koen10).
  Mass=0.586+-0.007Msun(Torres10), R=0.52+-0.05Rsun(Gaidos14).  Teffs:
  3454+-50K(Houdebine12), 3500+-100K(Torres10),
  3506K(Cenarro01,Sanchez-Blazquez06,Cenarro07), 3650K(Stelzer13),
  3788+-88K(Gaidos14) => 3506K. [Fe/H]=0.10+-0.13,
  0.12+-0.02(Newton14).  Note that GJ 570A appears to roughly solar
  metallicity. Forvielle99 derives dynamical masses of M(B) =
  0.586+-0.007 Msun, M(C) = 0.390+-0.005.

GJ 49 = G 243-052 = LHS 1179 = HIP 4872
  M1.5V: KeenanMcNeil76(stan),Garcia89,Hawley97
  M2V: Gunn83,Joy74,Vyossotsky43
 *M2+V: Gray03
  M1: Bidelman85(Kuiper)
  K5V: LjunggrenOja61(Jaschek64,Jaschek78),Sjogren64
  M3: Lee47

  Not sure why this star not used as an M1.5V standard after
  KeenanMcNeil76. vanLeeuwen07 plx = 100.40+-1.52 mas. V=9.552+-0.015
  (Mermilliod91), B-V=1.503+-0.005(Mermilliod91),
  U-B=1.21+-0.058(Mermilliod91). J=6.230+-0.021(2MASS),
  H=5.582+-0.024(Mermilliod91), Ks=5.371+-0.020(2MASS).

GJ 625 = G 202-48 = HIP 80459 = 2MASS J16252459+5418148 = NLTT 42804 = Gaia DR2 1428427236986209024
  M0: Lee47
  M1.5V: Henry94,Reid95,Henry02(stan),Alonso-Floriano15
 *M2V: Vyssotsky56,Stephenson86,Lepine13(M2.0),Gaidos14(M2),Mann15(M2.1)
  sdM2.3e: Houdebine19
  M3: RojasAyala12(K-band)
  
  Only listed as standard in one reference (Henry02), and references
  over past decades go back and forth M1.5 and M2, and RojasAyala12
  lists even cooler type (M3) in near-IR, so probably not the best
  choice of standard (and seems consistently red and faint compared to
  other M1.5V standards).  Exoplanet host star
  (SuarezMascreno17). SIMBAD lists as Ursa Major group member, WDS
  lists it as WDS J16254+5418A = BWL 43A, but B appears to be 22nd
  magnitude star 5.4" away and no comment on common proper motion
  (single 2011 epoch) - but I've seen no other evidence it might be
  binary.  V=10.12(vanAltena95), V=10.111+-0.018(Mermilliod91),
  B-V=1.58(vanAltena965), B-V=1.603+-0.005(Mermilliod91),
  U-B=1.280(Mermilliod91), J=6.608+-0.020(2MASS),
  H=6.063+-0.018(2MASS), Ks=5.833+-0.024(2MASS),
  G=9.139769+-0.002794(GaiaEDR3), V-Ks = 10.111 - 5.833 =
  4.278. plx=154.3503+-0.0161mas(GaiaEDR3) => Mv = 11.054+-0.018, M_Ks
  = 6.776+-0.024, M_G=10.082.  Published metallicities come up
  consistently metal-poor: [Fe/H]=-0.26+-0.16(Schweitzer19),
  -0.28+-0.13(Newton14), -0.35+-0.08(Mann15,Yee17),
  -0.40+-0.09(Maldonado20), -0.41(Neves13#2), -0.42(Neves13#1),
  -0.44+-0.20(Gaspar16=Jenkins09,Ammons06),
  -1.054+-0.018(Xiang19). Photometric metallicity estimates using
  calibration of JohnsonApps09 yields [Fe/H]=-0.44, and
  SchlaufmanLaughlin10 yields [Fe/H]=-0.73.  So there seems to be
  clustering of values around [Fe/H] ~ -0.4. Teffs: 3350K(Jenkins09),
  3364+-104K(Sebastian21), 3365K(Anders19), 3460K(Lepine13),
  3464+-17K(RojasAyala12), 3475+-60K(Mann15#1), 3490K(Reiners20),
  3490+-62K(Gaidos14#2), 3494+-73K(Gaidos14#1), 3499K(Stassun18),
  3500K(MartinezRodriguez19), 3500K(Rajpurohit18),
  3512+-68K(Maldonado20), 3513+-79K(Muirhead18), 3516K(Passeger18),
  3525+-51K(Schweitzer19,Fuhrmeister19), 3540+-34K(Mann15#2),
  3549+-157K(Stassun19), 3557+-9K(Fouque18), 3570K(Morales08),
  3575K(Stelzer13), 3576+-27K(Houdebine19), 3600K(Cifuentes20),
  3604K(Sarmento21), 3615K(Queiroz20), 3674+-64K(Johnsson20),
  4300K(Xiang19) => <Teff> ~ 3515K.  Best fit VOSA synthetic spectrum
  (EEM 7/20/2021): BT-NextGen-AGSS2009, Teff=3400K, logg=5, [M/H]=-1,
  Lum=0.01397+-0.00007765 Lsun => logL = -1.8548+-0.0024.
  Luminosities: L=0.0200+-0.0059Lsun=>logL=-1.699+-0.132(Gaidos14),
  L=0.01628+-0.00388Lsun=>logL=-1.7883+-0.1055(Stassun19,TICv8),
  L=0.014810+-0.000210Lsun=>logL=-1.8294+-0.0062(Martinez-Rodriguez19),
  L=0.01482+-0.000220Lsun=>logL=-1.8292+-0.0064(Schwietzer19),
  L=1.410491600e-02+-2.481219400e-04Lsun=>logL=-1.8506+-0.0076(Cifuentes20),
  logL=-1.8648+-0.0024(EEM,VOSA), logL=-1.86+-0.03(Magaudda20),
  logL=-1.883+-0.164(Maldonado20) => adopt Cifuentes20
  logL=-1.8506+-0.0076.


# Exemplars

GJ 908 = LHS 550 = BR Psc = HIP 117473 = Lal 46650
  M0V: Newton14(near-IR)
  M1V: Stephenson86,Henry94,Hawley97,Henry02
  M1V Fe-1: Keenan89
  M1.4: Mann15
 *M1.5V: Bidelman85(M1.5),Lepine13
  M2V: Vyssotsky43,JM53(non-stan),Cowley82(M2Ve),Torres06,Gaidos14
  M2.5Ve: Joy74
  M3: Lee47

  Type has mostly oscillated between ~M1 and ~M2 over the years.  :
  [Fe/H]=-0.95+-0.19, as does Mann15 [Fe/H]=-0.45+-0.08.
  V=8.983+-0.012(Mermilliod91), B-V=1.464+-0.028(Mermilliod91),
  U-B=1.104+-0.025(Mermilliod91), J=5.827+-0.023(2MASS),
  H=5.282+-0.031(2MASS),
  Ks=5.043+-0.020(2MASS). V-Ks=3.940(Mermilliod91,2MASS). mbol =
  7.503+-0.025 (JHK => Casagrande08 calib.) => BCv = -1.48, BC_K =
  2.46.  Plx = 167.29+-1.23 mas. Mv=10.10+-0.02(Mermilliod91,
  vanLeeuwen07), M_Ks=6.16+-0.03(2MASS,vanLeeuwen07).  This star was
  also modeled by Leggett96: flux = 2.50e-11 W/m^2, logL=-1.59,
  mbol=7.53, Mbol=8.74, BCv=-1.45, BC_K=2.48.  Teffs:
  3646+-60K(Mann15#1), 3700+-150K(Leggett96), 3704+-29K(Mann15),
  3712+-85K(Gaidos14) => adopt Teff=3700K. Nice to see the Leggett96
  and Casagrande08-derived mbol agree at the +-0.03 mag level!
  G=8.1496 0.0007, Bp-Rp=2.1050, Bp-G=1.0879, G-Rp=1.0170.

GJ 134 = HD 275122 = Wolf 1325 = LHS 1528 = HIP 15366 = 2MASS J03180742+3815081 = G 95-25 = G 78-31 = LTT 11082 
  K7: Cannon49
 *M1.5V: Joy74,Bidelman85(M1.5),Reid95/Hawley97(M1.5),Lurie13(M1.5),Mann15(M1.5)
  M2V: Vyssotsky46,Gaidos14(M2)
  M3: Lee47,Stephenson86(M3:)

  V=10.280(Mermilliod91), B-V=1.475(Mermilliod91),
  U-B=1.205(Mermilliod91).  Ks=6.164+-0.020(2MASS), V-Ks = 10.280 -
  6.164 = 4.116.  plx=62.5647+-0.0720mas(GaiaDR2).
  Mv=9.26(Mermilliod91,GaiaDR2).  M_Ks=5.146+-0.020(2MASS,GaiaDR2).
  G=9.4103 0.0006, Bp-Rp=2.1254, Bp-G=1.1107, G-Rp=1.0148.

GJ 366 = Ross 434 = LHS 2188 = HIP 47981 = G 252-44 = G 253-30 = LTT 12585 = NLTT 222468 = 2MASS J09464844+7602388
  M1: Lee47
 *M1.5V: Joy74,Bidelman85(M1.5),Reid95(M1.5),Lurie13(M1.5)
  M2V: Vyssotsky46,Gaidos14(M2)

  V=10.615+-0.015(Mermilliod91), V=10.64(Weis93),
  B-V=1.415+-0.015(Mermilliod91), B-V=1.40(Weis93), V-R=1.02(Weis93),
  R-I=0.87(Weis93), U-B=1.09+0.01(Mermilliod91),
  Ks=6.629+-0.024(2MASS), V-Ks=10.615 - 6.629 = 3.986.
  plx=63.3142+-0.0302mas. Mv = 9.623+-0.015 , M_Ks= 5.637+-0.024.
  G=9.7846 0.0007, Bp-Rp=2.1161, Bp-G=1.1053, G-Rp=1.0108.

LHS 2429 

LHS 1828 

G 242-48

BD+61 195

GJ 3098

GJ 87

tet Per B

2MASS J08175130+3107455

2MASS J14562809+1648342






# Other Stars

RECONS list shows GJ 887 (J2305-3551) as the nearest M1.5V star,
followed by GJ 15A (J0018+4401), & GJ 191 (J0511-4501). 

GJ 433 = LHS 2429 = HIP 56528 = L 907-1 = NLTT 27914 = SAO 202602 = 2MASS J11352695-3232232
  M1.46: Terrien15(Newton14/PMSU)
  M1.48: Terrien15(Newton14)
  M1.5: Reid95,Terrien15
  M2: Upgren72,Bidelman85(M2),Henry02("GJ 433 AB"),Gaidos14(M2)
  M2.2+-0.5: Sebasian21

  Nearby (d=9pc) exoplanet host (Feng20). Is it a binary?  Henry02
  notes "GJ 433 is a known close binary system (Bernstein 1997)" and
  "only for GJ 190 and GJ 433 do the trigonometric and spectroscopic
  distances differ by more than a factor of 2." However GJ 433 does
  not have a WDS entry in the modern catalog - however Malkov12 lists
  it as WDS 11355-3232 and lists Period = 1.369717+-0.087382 yr and
  a=0.0043+-0.0020" (Grade9). Bernstein97 reported astrometric
  perturbation in Hipparcos consistent with P=523.6+-36.9d,
  a1=6.9+-2.2mas, M2=0.03+-0.01Msun, i=63.3+-20.5deg.  Feng20 reports
  3 planets, but all with amplitudes K < 3m/s, with the outermost one
  (M=32+-6 Mearth, P=5094d) being a "super-Neptune" (Feng20) - no
  mention of a stellar companion, and no RV signal near the period
  reported by Bernstein97.  Bonfils13 lists a trend of dv/dt = 0.15
  m/s/yr. However Kervella22 lists tangential velocity anomaly
  3.29+-2.31 m/s, so negligible.  plx=110.1711+-0.0204mas(GaiaDR3).
  V=9.81(HIP), V=9.813513(GaiaDR3), V=9.816+-0.024(Mermilliod91),
  V=9.84(TYC), B-V=1.492+-0.015(Mermilliod91), U-B=1.17(Mermilliod91),
  Ks=5.623+-0.021(2MASS), V-Ks = 9.813 - 5.623 = 4.19.  Teffs:
  3472+-96K(Casagrande08), 3580K(EEM SED fit, see below),
  3584+-41K(Houdebine19), 3600K(Morales08), 3600K(Rajpurohit13),
  3605K(Suissa20), 3609+-90K(Muirhead18), 3616K(Lindgren17),
  3649K(Reiners20), 3654+-105K(Sebastian21), 3707+-99K(Gaidos14).
  Luminosity: logL=-0.46610+-0.00635(GaiaDR3,FLAME),
  logL=-1.4001+-0.1221(Gaidos14),
  logL=-1.4692+-0.0067(Martinez-Rodriguez19),
  logL=-1.4747+-0.1039(Stassun19/TIC), logL=-1.475(EEM,see below).
  Mass: 0.46+-0.05Msun(Maldonado20), 0.467+-0.014Msun(Paegert21),
  0.47Msun(Bonfils13), 0.47+-0.01Msun(Sebastian21),
  0.47+-0.03Msun(Neves13), 0.47+-0.05Msun(Santos13,Maldonado19),
  0.48Msun(Feng20), 0.49Msun(Reiners20), 0.52+-0.07Msun(Gaidos14),
  0.527+-0.003Msun(Muirhead18) => 0.47Msun.  Using Mann18 M_Ks
  calibration for GaiaDR3 metallicity, I get M=0.4666+-0.0180 Msun,
  similar to Paegert21and Sebastian21.  Metallicity:
  [Fe/H]=-0.17+-0.09(Goda19), [Fe/H]=-0.13(Terrien15),
  [Fe/H]=-0.0756(GaiaDR3), [Fe/H]=-0.02+-0.05(Lindgren17).
  logg=4.81(Lindgren17).  SED fit 7/16/2022: Teff=3580K, BCv=-1.580,
  mbol=8.233, Mbol=8.443, logL=-1.475.