K0V Garrison94 lists sig Dra as a K0V anchor standard, and MK73 lists sig Dra as a secondary standard. Keenan80 calls sig Dra a "defining zero point" as the K0V standard. See notes on the late-G/early-K series of standards at the bottom. 54 Psc (=HD 3651) also appears to be a good standard. MK43 standards: sig Dra, 70 Oph A, 54 Psc - K0V JM53 standards: sig Dra, 70 Oph A, 54 Psc, HD 124752 - K0V Wilson62 standards: sig Dra, 70 Oph A, 54 Psc, HD 124752 - K0V [from JM53] Morgan65 standard: omi^2 Eri - K0V MorganKeenan73 stan: sig Dra - K0V (non-dagger standard) Houk75 standard: 54 Psc - K0V (primary standard) KeenanMcNeil76 stan.: sig Dra - K0V Keenan80 standard: sig Dra - K0V ("defining zero point"!) 54 Psc (=HD 3651) - K0+V HD 224618 - K0V Keenan83 standard: sig Dra (=HD185144) - K0V HD 224618 - K0V 54 Psc (=HD 3651) - K0+V Keenan85 standard: sig Dra (=HD 185144) - K0V HR 7368 (="BS 7368" = HD 182488) - K0V Corbally86 standard: HD 284253 (= vB 21) - K0V Keenan88 standard: sig Dra (=HD 185144) - K0V HD 224618 - K0V Keenan89 standards: sig Dra (=HD 185144) - K0V HD 224618 - K0V HD 26965 - K0V 54 Psc (=HD 3651) - K0V Strassmeier90 stan: sig Dra (=HR 7462) - K0V GrayAtlas standard: sig Dra - K0V GrayNstars standard: 54 Psc (=HD 3651) - K0V HD 224618 - K0V Pecaut13 standard: 54 Psc (=HD 3651) - K0V Skiff08 flags three stars as MK standards (all from Keenan89): HD 185144, HD 224618, and HD 26965. (K0V) = 0.84 ; Wilson62; 8 Hyads (K0V) = 0.831 ; median of 3 Morgan65 K0V stars (K0V) = 0.824 [+-0.011 sem,+-0.056 stdev]; med. for 48 K0V stars ARICNS (K0V) = 0.822 ; 216 HIP d<75pc (+-0.004 sem, +-0.049 stdev) (B-V)(K0V) = 0.82 ; JohnsonMorgan53, Johnson66, KenyonHartmann95 (K0V) = 0.818 ; 40 Gray01/03/06 K0V stars (+-0.009 sem, +-0.057 stdev) (K0V) = 0.81 ; Fitzgerald70 (B-V)(K0V) = 0.81 ; SchmidtKaler82 (B-V)(K0V) = 0.79 ; Strassmeier90 (B-V)(K0V) = 0.786 ; anchor stan. K0V sig Dra (B-V)(K0V) = 0.773 ; sec. stan. K0V HD 224618 (K0V) = 0.761 ; Crawford76 => adopt (B-V)(K0V) = 0.816 *** => adopt (U-B)(K0V) = 0.436 => adopt (V-I)(K0V) = 0.853 => adopt (V-R)(K0V) = 0.443 => adopt (R-I)(K0V) = 0.410 => adopt (V-J)(K0V) = 1.475 => adopt (V-H)(K0V) = 1.862 => adopt (V-Ks)(K0V) = 1.953 => adopt (H-Ks)(K0V) = 0.091 => adopt (J-H)(K0V) = 0.387 => adopt (K-W1)(K0V) = 0.030 => adopt (G-V)(K0V) = -0.196 Gray01/03/06 list 40 nearby K0V stars. Median HIP colors: (K0V) = 0.818 (+-0.009 sem, +-0.057 stdev; N=40) (K0V) = 0.857 (+-0.006 sem, +-0.038 stdev; N=40) For Hipparcos K0V stars within 75pc, parallax S/N > 8, and within 1 mag of the main sequence (N=216): (K0V) = 0.822 (+-0.004 sem, +-0.049 stdev) (K0V) = 0.856 (+-0.004 sem, +-0.044 stdev) (K0V) = 1.486 (+-0.009 sem, +-0.109 stdev) (K0V) = 1.873 (+-0.012 sem, +-0.149 stdev) (K0V) = 1.975 (+-0.014 sem, +-0.154 stdev) (K0V) = 0.392 (+-0.004 sem, +-0.046 stdev) (K0V) = 0.101 (+-0.002 sem, +-0.031 stdev) (K0V) = 0.947 (+-0.004 sem, +-0.073 stdev) (K0V) =-0.086 (+-0.002 sem, +-0.027 stdev; N=212) (K0V) = 2.800 (+-0.012 sem, +-0.187 stdev; N=216) (U-B)(K0V) = 0.450 ; HIP d<75pc S/N>8 K0V N=95 (Mermilliod91 photometry) (U-B)(K0V) = 0.47 ; Johnson66 (U-B)(K0V) = 0.48 ; JohnsonMorgan53 Teff(K0V) = 5172 K ; Ramirez05 Teff calibration for B-V=0.816 Teff(K0V) = 5215 K ; Napiwotzki93 Teff calibration for B-V=0.816 Teff(K0V) = 5230 K ; mean photometric Teff Teff(K0V) = 5250 K ; Schmidt-Kaler82 Teff(K0V) = 5265 K ; pri. stan. sig Dra (see below) *** Teff(K0V) = 5272 +- 19 K ; Pecaut13 (GJ 631) Teff(K0V) = 5278 K ; Casagrande10 Teff calibration for B-V=0.816 Teff(K0V) = 5288 K ; sec. stan. HD 224618 (see below) Teff(K0V) = 5294 K ; median of 406 Teff estimates for K0V stars Teff(K0V) = 5300 K ; smoothed Teff(SpT) trend Teff(K0V) = 5300 K ; GrayCorbally94 Teff(K0V) = 5328 K ; Biazzo07 Teff calibration for B-V=0.816 Teff(K0V) = 5347 +- 20 K ; Boyajian12b Teff(K0V) = 5280 K ; GrayCorbally09 Teff(K0V) = 5450 K ; Boyajian12a (N=5) => adopt Teff(K0V) = 5290 K (logT = 3.723) [updated 10/27/2017] BCv(K0V) = -0.240 mag ; Schmidt-Kaler82(fixed typo? BCv=-0.37 + 0.13 offset) BCv(K0V) = -0.237 +- 0.024 ; non-standard GJ 631 (12 Oph) (Pecaut13) BCv(K0V) = -0.202 mag ; EEM fit to Casagrande06/08/10 (Teff=5280K) BCv(K0V) = -0.190 mag ; Flower96(Teff=5280K) BCv(K0V) = -0.182 mag ; Masana06(Teff=5280K) BCv(K0V) = -0.174 mag ; Bessell98(ATLAS9,logg=4.5,Teff=5280K) BCv(K0V) = -0.166 mag ; Bertone04(Teff=5280K) => adopt BCv(K0V) = -0.182 mag (+-0.014 rms systematic) Mv(K0V) = 5.9 mag ; GrayCorbally09 Mv(K0V) = 5.9 mag ; Schmidt-Kaler82 Mv(K0V) = 5.76 mag ; B-V=0.816 => Mv(Wright05) Mv(K0V) = 5.32 mag ; Wegner07 => adopt Mv(K0V) = 5.76 mag logL(K0V) = -0.329 dex ; Mv=5.76, BCv=-0.182 => Mbol = 5.578 => adopt logL(K0V) = -0.329 dex => adopt Mbol(K0V) = 5.578 mag Mass(K0V) = 0.98 Msun ; EEM Teff vs. Mass fit for binaries (Teff=5260K) Mass(K0V) = 0.89 Msun ; EEM Mv vs. Mass fit for binaries (Mv=5.76) Mass(K0V) = 0.87 Msun ; EEM logL vs. Mass fit for binaries (logL=-0.33) Mass(K0V) = 0.866 Msun ; Eker15 calibration for logL=-0.11 => adopt Mass(K0V) = 0.87 Msun [last updated 8/2/2018] Rad(K0V) = 0.7956 +- 0.0076 Rsun ; Boyajian12b (N=5) # Anchor Standard HD 185144 = sig Dra = GJ 764 (J1932+6939) G8V: Lindblad22,Adams35,Morgan38 G8.5V: Morgan38 G9V: Keenan41,Bidelman85(G9),Gray03 *K0V: MK43(stan),Nassau47,JM53,Roman55,Wilson62,MK73(non-standard),KeenanMcNeil76(stan),Keenan85,Keenan88,Keenan89,Garrison94,GrayAtlas K2Ve: Christian01 Garrison94 calls it the K0V anchor standard, although pre-MK43 works had it at G8V or G9V, and Gray03 pulls it 1 subtype hotter (G9V). Apparently slightly metal poor [Fe/H]=-0.15 (Takeda+2007). B-V(HIP)=0.786+-0.007, V-I(HIP)=0.85+-0.02, U-B(Mermilliod91)=0.386+-0.012. V(HIP)=4.67, Ks(2MASS) = 2.900+-0.324(poor). PASTEL median values: = 5265 K, [Fe/H] ~ -0.2. # Secondary Standard HD 224618 = LHS 552 = BD-17_6856 (J2359-1656) G6V: Adams35 *K0V: Roman55,Cowley67,McNeil86,Keenan80,Keenan83,Keenan88,Keenan89(stan) K2: Bidelman85 No published types since Keenan89. Nice agreement among Roman, Cowley, Keenan. Metal poor. B-V=0.785+-0.032 (HIP), B-V=0.773+-0.009(Mermilliod91). PASTEL medians: = 5288K (N=2), logg=4.5+-0.2 (Tomkin99), [Fe/H]=-0.76+-0.06(Tomkin99), [Fe/H] = -0.59 (Casagrande11). # Deprecated Standards HD 3651 = 54 Psc = HR 166 (J0039+2115) K0V: MK43,JM53,Wilson62(Balmer lines weak, CN strong),Jaschek64(all),Cowley67,HoukStandard,Gray03,Pecaut13 K0+V: Keenan80,Keenan83,KeenanYorka85,Hoffleit91 *K0.5V: Keenan89(stan) K0III: Keenan88(error?) K1V: Adams35,Bidelman85(K1) K2V: Yoss61 Decent agreement among MK43, JM53, Cowley, Houk, Gray on K0V subtype, but in the 1980s Keenan started moving it 0.25-0.5 subtype cooler and ended with it as K0.5V standard (1989). I'm assuming this meant he thought it was a bit cooler than sig Dra and HD 224618. 54 Psc was not the first choice of standard for PecautMamajek13, but it was observable during the survey. I can only assume the "K0III" classification in Keenan & Yorka (1988) was in error. Has T8 companion 43" away. PASTEL median values: = 5214K (N=18), <[Fe/H]>= +0.13 (N=15). B-V=0.850+-0.009(HIP), V=5.88(HIP). HD 26965 = omi^2 Eri = GJ 166A = HR 1325 (J0415-0739) G9V: Abt85 K0V: Wilson62,Morgan65,Keenan99 *K0.5V: Keenan88,GrayNstars(stan),Gray06 K1-V: Keenan83,Keenan85 K1V: Roman55,Bidelman85(K1),Gray03 Morgan65 calls omi2 Eri the K0V "fundamental classification standard". Keenan migrated its type blueward over two decades, going from K1-V (1983,1985) to K0.5V (1988) to K0V (1999). PASTEL medians: = 5153 K (N=25), <[Fe/H]> = -0.28 (N=18). B-V=0.816+-0.005(Mermilliod91), U-B=0.446+-0.009(Mermilliod91), V=4.424+-0.012(Mermilliod91). HD 165341 = 70 Oph A = HR 6752 = GJ 702 *K0-V: Keenan89,Gray03 K0V: MK43,JM53,Wilson62,Cowley67,Abt81(AB) K0+V: Keenan41 K0.5V: Morgan38 K1V: Adams35 Not ideal as 70 Oph is a 1.5" binary (K4V companion) and type has migrated from K0V to K0-V. Primary: V=4.25(Mermilliod91), B-V=0.78(Mermilliod91), U-B=0.57(Mermilliod91). HD 124752 = HIP 69400 = BD+67_771 (J1412+6735) *K0-V: Gray03 K0V: Cannon(K0),Roman49,JM53,Jaschek64(all) K0.5V: Keenan80,Keenan89 K1V: Wilson50,LevatoAbt78 5" binary with M2V star (Gray03). Ursa Major member. Type has migrated among the experts from K0V to K1V, indeed JM53, Keenan, and Gray all disagree on subtype. Probably not the best choice of standard. HD 284253 = Cl Melotte 25 21 = HIP 19934 = V984 Tau (J0416+2154) G7: Wilson48 *K0V: Wilson62(K0), Morgan65, Corbally86(stan,Morgan65) Very little history to it other than Morgan65. HD 182488 = GJ 758 = HR 7368 G8V: Wilson62 *G9+V: Gray03 K0V: Halliday55,Keenan85,Keenan89 K0IV: Hagen67 Keenan and Gray types disagree, probably not the best choice of standard. # Other Stars Morgan65 classified three Hyads as K0V: HD 28258 (B-V=0.839), 284253 (B-V=0.813), & 285773 (B-V=0.831). Median = 0.831. RECONS list shows GJ 702A (70 Oph A; J1805+0230) as the nearest K0V star. HD 10780 = HR 511 = HIP 8362 K0V: 1927MeUpp..28....1L,Lindblad34,Adams35,Keenan41,Brodskaya60,Ljunggren61,Wilson62,Cowley67,Bidelman85(K0) G9V: Morgan37,Gray03 G5V: 1932MeUpp..55....1S PASTEL: = 5350K(N=23), <[Fe/H]>=+0.02(N=18). V=5.63(HIP), B-V=0.804+-0.010(HIP), V-I=0.81(HIP). # Notes - Closer look at the G/K Boundary There seems to be some confusion among expert classifiers on the subtypes among the late Gs and early Ks, especially in the G8-K1 range. I suspect this is due to the subsolar metallicities of some of the standards that were adopted early on (e.g. Tau Ceti, HD 224618, Sigma Draconis, omi^2 Eri). The approximately solar metallicity standards 61 UMa (G8V), 107 Psc (K1V), and eps Eri (K2V). Interpolating between G8V (61 UMa) and K2V (eps Eri) standards, one would expect the solar metallicity K0V standard to have properties of Teff ~ 5291K. Interpolating between G8V (61 UMa) and K1V (107 Psc) standards, one would expect the solar metallicity K0V standard to have properties of Teff ~ 5296K. These agree with the Teff adopted previously (Teff = 5290K). Teff [Fe/H] B-V Name SpT(Gray03) 5495 -0.04 0.734 61_UMa G8V 5424 0.74 trend G8V 5390 -0.21 0.776 HD_4747 G9V 5300 -0.12 0.773 HD_82443 G9V 5350 +0.02 0.804 HD_10780 G9V(non-stan) 5345 0.75 trend G9V 5227 +0.04 0.78 70_Oph_A K0-V 5265 -0.2 0.786 sig_Dra G9V[but K0V anchor!] 5288 -0.59 0.785 HD_224618 [K0V;Keenan89] 5266 0.78 trend K0V 5214 +0.13 0.850 54_Psc K0.5V 5153 -0.28 0.816 omi02_Eri K0.5V 5226 0.80 trend K0.5V 5196 -0.04 0.836 107_Psc K1V 5186 0.83 trend K1V 5086 -0.09 0.882 epsEri K2V 5207 -0.2 0.941 NO_UMa K2V 5012 -0.19 0.876 HD166620 K2V 5107 0.90 trend K2V B-V vs SpT is quadratic, suggesting negligible diff between G9V and K0V, but Teff vs. SpT trend is roughly linear: Teff[K] = 5266 - 79.176*SpT(K-subtype) [G8V = -2, K0V = 0, K2V = 2] # Data on Teff & B-V trend for stars hotter and cooler than K0V These data are used to construct a smoothed Teff vs. SpT trend to assist in assigning Teffs to some spectral types lacking in strong standard stars or with standards that are poorly characterized. # SpT # Name B-V Teff/K Notes Standard Status $ F0V -20 HD23585 0.297 7200 Teff(phot) primary $ F0V -20 HD195627 0.288 7221 [Fe/H]=-0.11 candidate $ F1V -19 37UMa/HD91480 0.335 6990 ? primary $ F2V -18 78UMa/HD113139 0.368 NA ? primary $ F3V -17 HD26015/HR1279 0.397 6805 Hyad primary $ F3V -17 46Tau/HD26690 0.366 6864 ? secondary $ F4V -16 HD27561 0.412 6695 Hyad primary $ F5V -15 HD27524 0.434 6580 Hyad primary $ F5V -15 HD27534 0.441 6572 Hyad secondary $ F5V -15 45Boo/HD134083 0.429 6573 [Fe/H]~0.0 secondary $ F5V -15 iotPeg/HD210027 0.435 6470 [Fe/H]=-0.15 tertiary $ F6V -14 pi3Ori/HD30652 0.484 6424 [Fe/H]=+0.01 anchor $ F6V -14 gamSer/HD142860 0.478 6268 [FE/H]=-0.2 secondary $ F6V -14 38Cas/HD9021 0.464 6298 ? candidate $ F7V -13 tetPer/HD16895 0.514 6297 [Fe/H]=-0.01 primary $ F7V -13 iotPsc/HD222368 0.507 6185 [Fe/H]=-0.17 secondary $ F7V -13 70Tau/HD27991 0.490 6417 [FE/H]=0.07 candidate $ F8V -12 HD27808 0.518 6250 [Fe/H]=+0.11 primary $ F8V -12 36UMa/HD90839 0.541 6170 [Fe/H]=-0.15 secondary $ F9V -11 HD10647 0.551 6143 [Fe/H]=-0.02 secondary $ G0V -10 betCVn/HD109358 0.588 5882 [Fe/H]=-0.09 primary $ G0V -10 iotPer/HD19373 0.595 5953 [Fe/H]=+0.08 secondary $ G0V -10 kapFor/HD14802 0.597 5886 [Fe/H]=-0.10 tertiary $ G1V -9 HD27836 0.604 5793 Hyad primary $ G1V -9 HD115043 0.602 5850 [FE/H]=-0.08 secondary $ G1V -9 zet2Ret/HD20807 0.600 5858 [Fe/H]=-0.24 tertiary $ G2V -8 Sun 0.653 5772 [FE/H]=0.00 anchor $ G2V -8 18Sco/HD146233 0.652 5795 [Fe/H]=+0.04 secondary $ G2V -8 HD76151/HR3538 0.661 5775 [Fe/H]=+0.09 tertiary $ G2V -8 HD2141/HIP2014 0.647 5727 ? tertiary $ G3V -7 16CygB/HD186427 0.661 5752 [Fe/H]=+0.06 primary $ G3V -8 HD26736 0.657 5762 [Fe/H]=+0.15 tertiary $ G5V -5 kapCet/HD20630 0.681 5712 [Fe/H]=+0.05 anchor $ G5V -5 HD120690/HR5209 0.703 5582 [Fe/H]=-0.05 secondary $ G5V -5 HD26756 0.693 5642 [Fe/H]=+0.15 tertiary $ G5V -5 HD110619 0.664 5611 [FE/H]=-0.41 candidate $ G7V -3 HD111395 0.703 5636 [Fe/H]=+0.10 candidate $ G8V -2 61UMa/HD101501 0.723 5495 [Fe/H]~-0.04 anchor $ G8V -2 tauCet/HD10700 0.727 5352 [Fe/H]=-0.53 secondary $ G8V -2 11LMi/HD82885 0.770 5520 [Fe/H]~+0.36 tertiary $ G8V -2 HD27130 0.756 5317 [Fe/H]~+0.1 tertiary $ K0V 0 sigDra/HD185144 0.786 5265 [Fe/H]~-0.2 anchor $ K0V 0 HD224618 0.773 5288 [Fe/H]~-0.6 secondary $ K1V 1 107Psc/HD10476 0.836 5196 [Fe/H]~-0.04 primary $ K2V 2 epsEri/HD22049 0.882 5086 [Fe/H]=-0.09 anchor $ K2V 2 NOUMa/HD109011 0.941 5207 [Fe/H]=-0.2 secondary $ K2V 2 HD166620/HR6806 0.876 5012 [Fe/H]=-0.19 tertiary $ K3V 3 HD219134/HR8832 1.000 4829 [Fe/H]=-0.04 primary $ K3V 3 HD16160/HR753 0.970 4860 [Fe/H]=-0.10 primary $ K3V 3 NPUMa/HD110463 0.955 4950 [FE/H]=-0.1? secondary $ K3V 3 HD128165/GJ556 0.997 4792 [Fe/H]=0.00 tertiary $ K4V 4 TWPsA/GJ879 1.094 4599 [Fe/H]=+0.03 primary $ K4V 4 KXLib/GJ570A 1.110 4616 [Fe/H]=+0.02 secondary $ K4V 4 GJ689/HD160964 1.100 4499 ? secondary $ K5V 5 61CygA/GJ820A 1.069 4383 [FE/H]=-0.25 primary $ K5V 5 HD36003/GJ204 1.135 4590 [Fe/H]=-0.11 secondary $ K5V 5 HD154363/GJ653 1.100 4340 [Fe/H]=-0.62 tertiary $ K6V 6 GJ529/HD120467 1.257 4356 [Fe/H]=+0.24 primary $ K6V 6 GJ39/HD4913 1.194 4232 [Fe/H]=+0.08 candidate $ K7V 7 61CygB/HD201092 1.309 4020 metalpoor primary $ K7V 7 GJ673/HD157881 1.359 4050 [Fe/H]=+0.11 secondary $ K7V 7 GJ786/HD193202 1.320 4170 ? secondary $ K7V 7 GJ380/HD88230 1.326 3990 ? tertiary $ K7V 7 GJ764.1B NA 4320 ? tertiary $ K7V 7 GJ265A/HIP34222 1.320 4320 ? tertiary $ K7V 7 GJ394/HD237903 1.352 4070 [Fe/H]=-0.07 tertiary $ K7V 7 GJ748.2A 1.206 NA ? tertiary $ K7V 7 etaCasB/GJ34B 1.393 NA ? tertiary $ M0V 10 GJ270/LHS1912 1.42 3763 ? primary $ M0V 10 GJ328 1.40 3870 ? secondary $ M0V 10 GJ839/LHS3727 1.366 3835 ? candidate $ M0.5 10.5 GJ846/HD209290 1.453 3810 [FE/H]=0.03 primary $ M0.5 10.5 GJ96 1.497 3840 [Fe/H]=0.14 secondary $ M0.5 10.5 GJ4B/HD38B 1.50 3900 ? tertiary $ M1V 11 GJ229A/HD42581 1.484 3700 ? primary $ M1V 11 GJ412A/Lal21258 1.532 3664 [Fe/H]=-0.43 secondary $ M1V 11 GJ514/LHS352 1.497 3670 ? secondary $ M1V 11 GJ424/SZUMa 1.419 3640 ? tertiary $ M1.5 11.5 GJ205 1.474 3750 [Fe/H]=0.49 primary $ M1.5 11.5 GJ880 1.512 3750 [Fe/H]=0.21 secondary $ M1.5 11.5 GJ526 1.448 3650 [Fe/H]~-0.2 tertiary $ M2V 12 GJ411/Lal21185 1.508 3570 [Fe/H]=-0.38 primary $ M2V 12 GJ382 1.503 3615 ? secondary $ M2V 12 GJ745B/LHS3433 1.570 3482 [Fe/H]=-0.35 tertiary $ M2V 12 GJ220 1.50 3791 ? tertiary $ M2V 12 GJ91 1.494 3570 ? tertiary $ M2.5 12.5 GJ381/LHS2230 1.573 3500 ? primary $ M2.5 12.5 GJ250B 1.449 3500 [Fe/H]=+0.14 seconary $ M2.5 12.5 GJ226 1.524 3520 ? tertiary $ M3V 13 GJ752A/HD180617 1.464 3368 [Fe/H]=+0.08 primary $ M3V 13 GJ251/HD265866 1.585 3400 [Fe/H]=-0.02 secondary $ M3V 13 GJ436/Ross905 1.493 3477 [Fe/H]=-0.02 secondary $ M3V 13 GJ725A/LHS58 1.537 3445 [Fe/H]~-0.4 secondary $ M3V 13 GJ687 1.505 3489 ? secondary $ M3V 13 GJ109/LHS1439 1.550 3390 ? tertiary