M9.5V

Kirkpatrick(in GrayCorbally09) lists BRI 0021-0214 as the primary
M9.5V standard, and cites Kirkpatrick95 and Kirkpatrick99.

ReinersBasri09 finds that the mean kinematic age of nearby M7-M9.5 stars is 3.1 Gyr. 

(V-Ic) = 4.73  ; trend Dieterich14 SpT vs. V-I
(V-Ic) = 4.788 ; pri. stan. BRI 0021-0214 (see below)
=> adopt (V-Ic)(M9.5V) = 4.73 [updated 7/4/2020]

V-Rc = 2.51       ; pri. stan. BRI 0021-0214 (see below)

(Bp-Rp)(M9.5V) = 4.8600 ; BRI_0021-0214 GaiaDR2
=> adopt (Bp-Rp)(M9.5V) = 4.86 [updated 12/10/2018]

(G-Rp)(M9.5V) = 1.6024 ; BRI_0021-0214 GaiaDR2
(G-Rp)(M9.5V) = 1.612  ; M6.5-L2 color trend 
=> adopt (G-Rp)(M9.5V) = 1.61 [updated 11/18/2020]

(Bp-G)(M9.5V) = 3.2576 ; BRI_0021-0214
=> adopt (Bp-G)(M9.5V) = 3.26 [updated 12/10/2018]

(G-V)(M9.5V) = -3.2143 ; BRI_0021-0214
(G-V)(M9.5V) = -3.10   ; trinomial trend through late Ms
=> adopt (G-V)(M9.5V) = -3.10 [updated 12/10/2018]

(V-Ks)(M9.5V) = 9.31 ; LEHPM1-0494B (Dieterich14)
(V-Ks)(M9.5V) = 9.29 ; smoothed fit to Dieterich SpT vs V-Ks
(V-Ks)(M9.5V) = 9.29 ; trend fit to Dahn17 for M9.5V
(V-Ks)(M9.5V) = 9.27 ; pri. stan. BRI 0021-0214 (Dieterich14)
=> adopt (V-Ks)(M9.5V) = 9.30 [updated 8/17/2020]

(G-Ks)(M9.5V) =  5.796 ; exemplar G 216-7B = 2MASS J22373255+3922398
(G-Ks)(M9.5V) =  5.845 ; exemplar WISE J072003.20-084651.2 = Scholz's Star
(G-Ks)(M9.5V) =  5.915 ; exemplar 2MASSW J0109216+294925
(G-Ks)(M9.5V) = 5.96   ; M_G=16.44, M_Ks=10.48
(G-Ks)(M9.5V) =  6.008 ; exemplar 2MASS J22341394+2359559 
(G-Ks)(M9.5V) =  6.01  ; interp M9V(5.90)-L0V(6.12)
(G-Ks)(M9.5V) =  6.057 ; pri. stan. BRI 0021-0214
=> adopt (G-Ks)(M9.5V) = 5.96 [updated 12/27/2021]

(r-i)(M9.5V) = 1.877 (+-0.05 rms) ; West05 fit for (V-Ic)=4.73

(i-z)(M9.5V) = 1.821 ; poly fit to SIMBAD d<75pc M dwarfs for G-Ks=5.96
=> adopt (i-z)(M9.5V) = 1.82 [updated 12/27/2021]

(z-J)(M9.5V) = 2.391 (+-0.053 rms) ; poly fit to d<50pc SIMBAD M dwarfs for G-Ks=5.96
=> adopt (z-J)(M9.5V) = 2.39 [updated 12/27/2021]

(J-H)(M9.5V)  = 0.808(+-0.031 sem,+-0.048 stdev) ; N=4 M9.5V Cruz03
(J-H)(L0V)    =  0.76             ; adopted for L0V
(J-H)(M9.5V)  = 0.745(+-0.07 rms) ; SIMBAD trend for M9.5V d<30pc
(J-H)(M9V)    =  0.72             ; adopted for M9V
=> adopt (J-H)(M9.5V) = 0.745 [last updated 8/6/2020]

(H-Ks)(M9.5V) = 0.547(+-0.018 sem,+-0.028 stdev) ; N=4 M9.5V Cruz03
(H-Ks)(M9.5V) = 0.505 ; trend of Dieterich14 data for V-Ks=9.3
(H-Ks)(M9.5V) = 0.487 ; trend SIMBAD d<30pc M9-L dwarfs
=> adopt (H-Ks)(M9.5V) = 0.50 [last updated 8/6/2020]

(J-Ks)(M9.5V) = 1.352(+-0.041 sem,+-0.066 stdev) ; N=4 M9.5V Cruz03
(J-Ks)(M9.5V) = 1.331(+-0.040 sem,+-0.112 stdev) ; N=9 M9.5V Faherty09
=> adopt (J-Ks)(M9.5V) = 1.331 [last updated 9/6/2017]

(Ks-W1)(M9.5V) = 0.343 ; Dupuy12 trend
(Ks-W1)(M9.5V) = 0.414 ; Dupuy12 median (N=3;d<50pc)
=> adopt (Ks-W1)(M9.5V) = 0.35 [updated 12/28/2019]

Mv(M9.5V) =  19.10 ; exemplar WISE J072003.20-084651.2 = Scholz's Star      
Mv(M9.5V) =  19.33 ; pri. stan. BRI0021-0214
Mv(M9.5V) =  19.61 ; LEHPM1-0494B
Mv(M9.5V) =  19.75 ; EEM fit to Dieterich14 V-Ks=9.30
Mv(M9.5V) = 19.78 ; V-Ks=9.3, M_Ks=10.48
Mv(M9.5V) =  19.83 ; Dieterich14 calib V-Ks=9.30
=> adopt Mv(M9.5V)   = 19.78 [updated 12/27/2021; M_Ks=10.48, V-Ks=9.3]
=> adopt M_G(M9.5V)  = 16.44 [updated 12/27/2021; M_Ks=10.48, G-Ks=5.96]
=> adopt M_Ks(M9.5V) = 10.48 [updated 12/27/2021; V-Ks=9.3, Mv=19.78]

M_G(M9.5V) =  16.11 ; pri. stan. BRI 0021-0214 = V* DY Psc
M_G(M9.5V) =  16.12 ; exemplar PC 0025+0447 (large uncertainty +-0.17)
M_G(M9.5V) = 16.13 ; trend for d<20pc late Ms/early Ls
M_G(M9.5V) =  16.16 ; exemplar WISE J072003.20-084651.2 = Scholz's Star      
M_G(M9.5V) =  16.36 ; exemplar G 216-7B = 2MASS J22373255+3922398
M_G(M9.5V) = 16.42 ; trend SIMBAD d<10pc sample
M_G(M9.5V) = 16.44 ; (G-Ks)=5.96, M_Ks=10.48
M_G(M9.5V) = 16.44 ; median for the d<20pc M9.5Vs in SIMBAD
M_G(M9.5V) =  16.51 ; 2MASS J22341394+2359559       
M_G(M9.5V) =  16.59 ; 2MASSW J0109216+294925

Note that the standard & exemplars have trend:
M_G = 9.0557 + 0.70024*M_Ks (rms = 0.098 mag)

M_Ks(M9.5V) =  10.03   ; exemplar PC 0025+0447 (large errors +-0.17)
M_Ks(M9.5V) =  10.05   ; pri. stan. BRI0021-0214 = DY Psc
M_Ks(M9.5V) =   10.30  ; LEHPM1-0494B
M_Ks(M9.5V) =  10.32   ; exemplar Scholz's star = WISE J072003.20-084651.2  
M_Ks(M9.5V) =  10.45   ; EEM fit to Dieterich14 V-Ks=9.30
M_Ks(M9.5V) = 10.475  ; halfway M_Ks=10.4(M9V) and M_Ks=10.57(L0V)
M_Ks(M9.5V) =   10.50  ; 2MASS J22341394+2359559 (single M9.5e classification;Gizis00)     
M_Ks(M9.5V) =  10.53   ; Dieterich14 calib (V-K=9.3, Mv=19.83)
M_Ks(M9.5V) =   10.55  ; median for SIMBAD M9.5 (d<25pc)
M_Ks(M9.5V) =  10.57   ; exemplar G 216-7B                     
M_Ks(M9.5V) =   10.67  ; 2MASSW J0109216+294925 (single M9.5 classification; Gizis00)

Teff(M9.5V) =   2495 K ; pri. stan. BRI 0021-0214 (Berger06)
Teff(M9.5V) =   2425 K ; pri. stan. BRI 0021-0214 (Golimowski04)
Teff(M9.5V) =  2403 K ; Dupuy17(Lyon model scale)
Teff(M9.5V) =  2383 K ; Dupuy17(SaumonMarley08 scale)
Teff(M9.5V) =   2351 K ; Golimowski04
Teff(M9.5V) = 2331 K ; empirical L-R relation, for logL=-3.572
Teff(M9.5V) =  2322 K ; Filippazzo15 calibration (M6V-T9V)
Teff(M9.5V) =  2315 K ; pri. stan. BRI 0021-0214 (Dieterich14)
Teff(M9.5V) =  2305 K ; LEHPM1-0494B (Dieterich14)
Teff(M9.5V) =  2298 K ; interp M9V(V-Ks=9.0,2380K)-L0V(V-Ks=9.4,2270K)
Teff(M9.5V) =   2225 K ; Cifuentes20 <Teff> for CARMENES(N=2)
=> adopt Teff(M9.5V) = 2330 K (logT = 3.368) [updated 11/15/2021]

BC_Ks(M9.5V) = 3.127 ; Filipazzo15 (field)
BC_K(M9.5V)  = 3.17  ; pri. stan. BRI 0021-0214 (Leggett01,UKIRT-IRCAM3)
BC_K(M9.5V)  = 3.17  ; interp M6V-L1V for V-Ks=9.30 
BC_K(M9.5V)  =  3.177 ; Golimowski04
=> adopt BC_K(M9.5V) = 3.17 [updated 11/3/2019]

BCv = -5.77 +-0.10 ; pri. stan. BRI 0021-0214 (see below)
BCv = -6.13 ; BC_K=3.17, V-K=9.30
=> adopt BCv(M9.5V) = -6.13 [updated 11/3/2019] 

logL(M9.5V) = -3.43 dex ; pri. stan. BRI 0021-0214 (Leggett01)
logL(M9.5V) = -3.45+-0.03 dex ; pri. stan. BRI 0021-0214 (Golimowski04; Mbol=13.37+-0.10
logL(M9.5V) = -3.505 dex ; pri. stan. BRI0021-0214 (Deiterich14)
logL(M9.5V) = -3.506 dex ; LEHPN1-0494B (Dieterich14) 
logL(M9.5V) = -3.572 dex ; M_Ks=10.5, BC_Ks=3.17, Mbol = 13.670
=> adopt logL(M9.5V) = -3.572 dex [updated 1/15/2021]
=> adopt Mbol(M9.5V) = 13.670 mag [updated 1/15/2021]

Mass(M9.5V) = 0.0777 Msun ; Mann18 calib. for M_Ks=10.50
=> adopt Mass(M9.5V) = 0.078 Msun [updated 11/15/2021]

Rad(M9.5V) = 0.0987 Rsun ; Teff=2350K, logL=-3.572
=> adopt Rad(M9.5V) = 0.099 Rsun [updated 11/3/2019]

# No Standards

Boeshaar85 does not list any standards later than dM9 (LHS 2924)

# Primary Standard

BRI 0021-0214 = DY Psc = 2MASS J00242463-0158201 = NLTT 1261 = LP 585-86
  M9.0V: Henry04
  M9+V: Tinney98
 *M9.5V: Kirkpatrick99(footnote#8),Reid99,Leggett01,Geballe02,Lodieu05,Kirkpatrick(GrayCorbally09)(pri),Liebert06(+-0.5subtype). 
  >=M9.5V: Kirkpatrick95("tenative classification")
  L0: Koen17
  L0.5: BardalezGagliuffi14(near-IR)

  SIMBAD note: "The name LP 585-86 is used for two different stars in
  NLTT catalogue (Vizier I/98) : the first one is at pos J2000 00 24
  24 -01 58.2, the second one at 00 38 51 +03 42.3", so the LP name
  should probably be avoided. Discovered by Irwin+1991. Kirkpatrick99
  consider BRI0021-0214 M9.5V in footnote #8 of their paper. Leggett01
  lists I = 15.10, K = 10.57, I-J=3.30, J-H=0.76, H-K=0.46, K-L'=
  0.79, flux = 8.17e-14 W/m^2, mbol = 13.74, BC_K = 3.17, log(L/Lsun)
  = -3.43, (M-m)=-0.42. Leggett01 IR photometry is on UKIRT-IRCAM3
  system. Golimowski04: Mbol=13.37+-0.10, logL=-3.45+-0.03. pmRA,
  pmDec = -80, +133 +- 4, 6 mas/yr (Faherty09) and Dist = 11.8+-0.6 pc
  (Faherty09). Leggett06 lists it as a standard star with J =
  11.754+-0.007, H=11.082+-0.001, K=10.500+-0.008. 2MASS photometry:
  J=11.922+-0.035, H=11.084+-0.022, Ks=10.539+-0.023
  (Cutri03). Leibert06 lists Cousins Rc=17.301+-0.006,
  Ic=15.022+-0.003, (R-I)c = 2.279, V-Rc = 19.81 - 17.301 =
  2.51. Patten06 lists IRAC photometry of [3.6]=9.94+-0.03,
  [4.5]=9.91+-0.03, [5.8]=9.72+-0.01,
  [8.0]=9.55+-0.01. Vmag=19.60(Jenkins09), Vmag=19.42(Reid04),
  Vmag=20.0(Glebock05), Vmag=19.19(Salim03),
  Vmag=19.81+-0.031(Dieterich14,CTIO),
  Vmag=20.01+-0.051(Dieterich14,SOAR) => adopt Vmag = 19.81. SDSS DR8
  reports: u = 22.520+-0.304, g = 21.070+-0.045, r = 18.677+-0.010, i
  = 16.182+-0.005, z = 14.370+-0.004. WISE photometry:
  W1=10.166+-0.024, W2=9.900+-0.019, W3=9.412+-0.039.  Derived colors:
  V-Ks = 19.81-10.539 = 9.271.  V-Ic = 19.81-15.022=4.788.  plx =
  79.9653 0.2212 mas (GaiaDR2). M_Ks=10.054+-0.024, Mv =
  19.325. Teffs: 2092K(Jenkins09), 2315K(Dieterich14),
  2425K(Golimowski04), 2495K(Berger06) => Teff=2425K.  Mass =
  0.103+-0.031 Msun(Jenkins09). (G-Ks)=6.057, M_G=16.111, M_Ks=10.054. 

# Exemplars

PC 0025+0447 = 2MASS J00274197+0503417  
 *M9.5V: Kirkpatrick92(M9.5pecV),Kirkpatrick93(M9.5e),Kirkpatrick95("tenative classification"),Kirkpatrick99(M9.5V(pec),footnote#8),Gagne14(optical)
  M9:: Graham92
  M9{gamma}: Gagne15("low-gravity")
  L0: Gagne15(IR),Martin17

  Kirkpatrick97 considered PC 0025+0447 a M9.5V star in their
  discussion. Kirkpatrick99 consider PC0025+0447 a M9.5V(peculiar) in
  footnote #8 of their paper. It is not explicitly listed as a
  secondary standard in the literature, but given the continuity of
  its classification by Kirkpatrick, it would seem to be an OK M9.5V
  secondary standard. Very similar absolute magnitudes to primary
  standard BRI 0021-0214, but both are systematically brighter than the others.  plx = 13.24+-1.56 mas(Dahn17),
  10.40+-0.80mas(Liu16). Unfortunately no parallax in either Gaia DR2
  or EDR3. J=16.189+-0.093(2MASS), H=15.288+-0.099(2MASS),
  Ks=14.964+-0.115(2MASS), K=14.94+-0.01(Skrzypek16,UKIDSS) =>
  M_K=10.03+-0.17(Skrzypek16,Liu16).  Gaia EDR3: G=21.0307+-0.0182,
  but no colors. M_G=16.12+-0.17(GaiaEDR3,Liu16).

G 216-7B = 2MASS J22373255+3922398 = KIR 5B = WDS J22375+3923C
  M9.5V: Kirkpatrick01,Cruz03

  This is a third component with two M3.5 stars situated 33" away.
  Deacon14 lists this object as "G216-7C", and although it is the "C"
  component to the WDS entry (J22376+3923), it is "G216-7B".
  Kirkpatrick01: "G216-7B lies very close to the hydrogen-burning
  limit".  Gaia EDR3: 47.6442+-0.1372mas, G=17.945925+-0.003048,
  E(BP/RP)=1.777, Bp-Rp=4.503721, Bp-G=2.969297, G-Rp=1.534424.
  (G-Ks)=5.796, M_G=16.363, M_Ks=10.567.

WISE J072003.20-084651.2 = Scholz's Star = 2MASS J07200325-0846499 
  M8.5-M9: Ivanov15(optical)
  M9.0+-0.7: Burgasser15(near-IR)
 *M9.5: Burgasser15(optical)
  M9.8: BardalezGagliuffi14
  L0+-1: Ivanov15(near-IR)

  Scholz's star - recently discovered M/L-boundary dwarf + mid-T dwarf
  binary which passed close to Sun ~80kya. Burgasser15 classifies the
  companion as T5, and says it only contributes 2% of the combined
  light in H-band.  Burgasser15(Table7) lists the primary as the only
  M9.5 within 10 pc.  plx=147.1+1.1-1.2mas(Dupuy19).
  B=20.778+-0.140(Ivanov15), V=18.266+-0.096(Ivanov15),
  R=15.838+-0.031(Ivanov15).  Burgasser estimates
  delta(K)=4.7+-0.4. K(A)=9.479+-0.019(Dupuy19). M=99+-6
  Msun(Dupuy19).  fbol = (2.18+-0.07)e-10 erg/s/cm2. Gaia EDR3:
  G=15.324036+-0.003086, E(BP/RP)=1.781, Bp-Rp=4.886625,
  Bp-G=3.341318, G-Rp=1.545307. Assuming all the V and G-band light is
  from A: (G-K)_A = 15.324 - 9.479 = 5.845, M_G(A)=16.16+-0.02,
  M_K(A)=10.32+-0.03, Mv(A)=19.10+-0.10.

2MASSW J0109216+294925
  M9.5: Gizis00

  G-Ks=5.915, M_G=16.585, M_Ks=10.670. 

2MASS J22341394+2359559
  M9.5e: Gizis00

  G-Ks=6.008, M_G=16.511, M_Ks=10.503.