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. Among the MK43 K0V standards, none of them really remains as a great standard - sig Dra (metal poor ~G9V), 70 Oph A (K0-V) 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"!) HD 224618 - K0V 54 Psc (=HD 3651) - K0+V Keenan83 standard: sig Dra (=HD 185144) - K0V HD 224618 - K0V 54 Psc (=HD 3651) - K0+V Keenan85 standard: sig Dra (=HD 185144) - K0V HR 7368 (="BS 7368" = HD 182488) - K0V 54 Psc (=HD 3651) - K0+V HD 224618 - K0V Kleinman86 standard: sig Dra (=HD 185144) - 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 Keenan99 standard: omi02 Eri (=HR 1325, HD 26965) - 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. (B-V)(K0V) = 0.846 ; median SIMBAD K0V d<25pc (N=36) (B-V)(K0V) = 0.845 ; Koen10 d<25pc median (N=6) (K0V) = 0.84 ; Wilson62; 8 Hyads (K0V) = 0.831 ; median of 3 Morgan65 K0V stars (B-V)(K0V) = 0.83 ; median CATSUP d<30pc K0V stars (N=26) (B-V)(K0V) = 0.827 ; exemplar HD 149661 = 12 Oph = HR 6171 (~solar metallicity) (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) (B-V)(K0V) = 0.813 ; ter. stan. HD 284253 = Cl Melotte 25 21 (B-V)(K0V) = 0.813 ; exemplar 20 Crt = HR 4458 (K0V) = 0.81 ; Fitzgerald70 (B-V)(K0V) = 0.81 ; SchmidtKaler82 (B-V)(K0V) = 0.807 ; interp G8V(B-V=0.730),K1V(B-V=0.845) (B-V)(K0V) = 0.804 ; exemplar HD 10780 (~solar metallicity) (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 *** [updated 8/29/2019] => 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 (Ks-W1)(K0V) = 0.070 ; EEM trend for d<30pc for B-V=0.816 => adopt (Ks-W1)(K0V) = 0.070 [updated 12/29/2019] (G-V)(K0V) = -0.248 ; exemplar HD 10780 (G-V)(K0V) = -0.245 ; exemplar 20 Crt = HR 4458 (G-V)(K0V) = -0.230 ; exemplar 55 Cnc (G-V)(K0V) = -0.229 ; trend SIMBAD d<20pc for V-Ks=1.953 (G-V)(K0V) = -0.227+-0.011 ; pri. stan. sig_Dra (G-V)(K0V) = -0.227+-0.008 ; sec. stan. HD_224618 (G-V)(K0V) = -0.222 ; smoothed fit f(SpT) G9V-M0V (G-V)(K0V) = -0.222 ; ter. stan. HD 284253 [Hyad] (G-V)(K0V) = -0.213 ; exemplar 12 Oph (G-V)(K0V) = -0.199 ; from fit for B-V=0.816 => adopt (G-V)(K0V) = -0.22 [updated 9/24/2021] (Bp-Rp)(K0V) = 0.9652 ; exemplar HD 10780 (Bp-Rp)(K0V) = 0.9786 ; ter. stan. HD 284253 [Hyad] (Bp-Rp)(K0V) = 0.9830 ; pri. stan. sig_Dra K0V (Bp-Rp)(K0V) = 0.9878 ; sec. stan. HD 224618 (Bp-Rp)(K0V) = 0.997 ; color trend for B-V=0.816 (Bp-Rp)(K0V) = 1.0025 ; exemplar 20 Crt = HR 4458 (Bp-Rp)(K0V) = 1.0102 ; exemplar *_12_Oph (Bp-Rp)(K0V) = 1.0135 ; exemplar 55 Cnc => adopt (Bp-Rp)(K0V) = 0.983 [updated 8/29/2020] (Bp-G)(K0V) = 0.451 ; color trend for B-V=0.816 (Bp-G)(K0V) = 0.430 ; Bp-Rp=0.983, G-Rp=0.553 (G-Rp)(K0V) = 0.5204 ; exemplar HD 10780 (G-Rp)(K0V) = 0.546 ; color trend for B-V=0.816 (G-Rp)(K0V) = 0.5492 ; exemplar 20 Crt = HR 4458 (G-Rp)(K0V) = 0.5519 ; ter. stan. HD 284253 [Hyad] (G-Rp)(K0V) = 0.5534 ; pri. stan. sig_Dra (G-Rp)(K0V) = 0.5565 ; exemplar 55 Cnc (G-Rp)(K0V) = 0.558 ; sec. stan. HD 224618 (G-Rp)(K0V) = 0.5758 ; exemplar *_12_Oph => adopt (G-Rp)(K0V) = 0.553 [updated 8/29/2020] => adopt (Bp-G)(K0V) = 0.430 [updated 8/29/2020; Bp-Rp=0.983, G-Rp=0.553] 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 (g-r)(K0V) = 0.602 ; Jordi06 (V-R)=>(g-r) for V-R=0.443 (g-r)(K0V) = 0.62 ; Covey07 (g-r)(K0V) = 0.666 ; Bilir05 (B-V)=>(g-r) for B-V=0.816 => adopt (g-r)(K0V) = 0.62 [updated 10/10/2020] 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) = 5270 K ; exemplar GJ 631 (~solar [Fe/H]; see below) Teff(K0V) = 5272 +- 19 K ; Pecaut13 (GJ 631) Teff(K0V) = 5275 K ; Teff for d<30pc [Fe/H]=+-0.1 dex dwarfs Hinkel17 for B-V=0.816 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) = 5270 K (logT = 3.723) [updated 9/26/2019] BCv(K0V) = -0.240 mag ; Schmidt-Kaler82(fixed typo? BCv=-0.37 + 0.13 offset) BCv(K0V) = -0.237 +- 0.024 ; exemplar GJ 631 (12 Oph) (Pecaut13) BCv(K0V) = -0.219 mag ; EEM fit to Casagrande06/08/10 (Teff=5270K), set so BCv(5772K)=-0.085 BCv(K0V) = -0.207 mag ; Flower96(Teff=5270K), set so BCv(5772K)=-0.085 BCv(K0V) = -0.200 mag ; Masana06(Teff=5270K), set so BCv(5772K)=-0.085 BCv(K0V) = -0.192 mag ; Bessell98(ATLAS9,logg=4.5,Teff=5270K, set so BCv(5772K)=-0.085) BCv(K0V) = -0.189 mag ; Casagrande18(Teff=5270K,logg=4.5, set so BCv(5772K)=-0.085 BCv(K0V) = -0.182 mag ; Bertone04(Teff=5270K), set so BCv(5772K)=-0.085) BCv(K0V) = -0.164+-0.02 ; exemplar 55 Cnc (metal-rich K0IV-V, see below) BCv(K0V) = -0.139+-0.018 ; exemplar GJ 631 (12 Oph) (see below) => adopt BCv(K0V) = -0.195 mag [last updated 9/26/2019, scale where BCv(5772K)=-0.085] Mv(K0V) = 6.15 mag ; sec. stan. HD 224618 [Fe/H] ~ -0.6! Mv(K0V) = 6.06 mag ; exemplar 20 Crt = HR 4458 Mv(K0V) = 5.91 mag ; median SIMBAD K0V d<25pc (N=38) Mv(K0V) = 5.9 mag ; GrayCorbally09 Mv(K0V) = 5.9 mag ; Schmidt-Kaler82 Mv(K0V) = 5.87 mag ; anchor stan. sig Dra (slightly metal poor) Mv(K0V) = 5.86 mag ; SIMBAD d<20pc trend for K stars V-Ks=1.95 (M_Ks=3.91) Mv(K0V) = 5.85 mag ; median Mv K0V d<20pc XHIP Mv(K0V) = 5.83 mag ; M_Ks=3.87 (median d<25pc; N=23) & V-K=1.953 Mv(K0V) = 5.78 mag ; exemplar HD 149661 = HR 6171 = 12 Oph = GJ 631 (solar) Mv(K0V) = 5.78 mag ; Koen10 median d<25pc K0V Mv(K0V) = 5.78 mag ; B-V=0.816 => CATSUP trend for d<30pc dwarfs Mv(K0V) = 5.76 mag ; B-V=0.816 => Mv(Wright05) Mv(K0V) = 5.75 mag ; CATSUP -0.1<[Fe/H]<0.1 d<30pc for B-V=0.816 Mv(K0V) = 5.73 mag ; Gray01/03/06 dwarfs, xHIP B-V/Mv, Gaspar16 |[Fe/H]|<0.05 "solar": fit for B-V=0.816 Mv(K0V) = 5.72 mag ; B-V=0.816 => EEM fit to SIMBAD dwarfs d<25pc Mv(K0V) = 5.62 mag ; exemplar HD 10780 (~solar metallicity) Mv(K0V) = 5.54 mag ; ter. stan. HD 284253 = Cl Melotte 25 21 [Hyad, [Fe/H] ~ +0.15] Mv(K0V) = 5.44 mag ; exemplar variant K0IV-V 55 Cnc = rho01 Cnc Mv(K0V) = 5.32 mag ; Wegner07 => adopt Mv(K0V) = 5.78 mag [updated 12/18/2020] (M_G=5.553, G-V=-0.227) => adopt M_G(K0V) = 5.553 mag [updated 12/18/2020] (Mv=5.78, G-V=-0.227) => adopt M_Ks(K0V) = 3.827 mag [updated 12/18/2020] (Mv=5.78, V-Ks=1.953) M_G(K0V) = 5.381 ; ter. stan. HD 284253 M_G(K0V) = 5.553 ; Mv=5.76, G-V=-0.227 M_G(K0V) = 5.5684 ; *_12_Oph K0V(k) M_G(K0V) = 5.629 ; SIMBAD d<20pc trend for V-Ks=1.953 M_G(K0V) = 5.6445 ; anchor *_sig_Dra K0V M_G(K0V) = 5.821 ; exemplar 20 Crt = HR 4458 M_K(K0V) = 3.87 ; median N=23 K0V d<25pc logL(K0V) = -0.338 dex ; Mv=5.78, BCv=-0.195 => Mbol = 5.585 => adopt logL(K0V) = -0.338 dex [updated 8/29/2020] => adopt Mbol(K0V) = 5.585 mag [updated 8/29/2020] Mass(K0V) = 0.888 Msun ; EEM Mv vs. Mass fit for binaries (Mv=5.76) Mass(K0V) = 0.879 Msun ; Eker18 calibration for logL=-0.330 Mass(K0V) = 0.879+-0.017 Msun ; ecl. binary HS Aur B (Popper86) Mass(K0V) = 0.865 Msun ; EEM logL vs. Mass fit for binaries (logL=-0.330) Mass(K0V) = 0.865 Msun ; Eker15 calibration for logL=-0.330 => adopt Mass(K0V) = 0.88 Msun [last updated 10/23/2019] Rad(K0V) = 0.873 +- 0.024 Rsun ; ecl. binary HS Aur B (Popper86) Rad(K0V) = 0.831 +- 0.004 Rsun ; deprecated stan. HD 165341 = 70 Oph A (Yee17) Rad(K0V) = 0.813 Rsun ; Teff=5270K, logL=-0.338 Rad(K0V) = 0.7956 +- 0.0076 Rsun ; Boyajian12b (N=5) Rad(K0V) = 0.778 +- 0.008 Rsun ; pri. stan. sig Dra (Yee17) Rad(K0V) = 0.772 Rsun ; exemplar HD 149661 = 12 Oph Rad(K0V) = 0.759 +- 0.012 Rsun ; exemplar HD 149661 = 12 Oph (Yee17) => adopt Rad(K0V) = 0.813 Rsun [updated 8/29/2020] # Anchor Standard HD 185144 = sig Dra = HR 7462 = GJ 764 (J1932+6939) G8V: Lindblad22,Adams35,Morgan38,Schalen48,1953UppAn...3h....W G8.5V: Morgan38 G9V: Keenan41,Bidelman85(G9),Gray03 G9/K0IV/V: 1972AbaOB..43..109W *K0V: MK43(stan),Nassau47,JM53,Roman55,Wilson62,MK73(non-standard),KeenanMcNeil76(stan),Keenan80,Keenan85,Keenan88,Keenan89,Garrison94,GrayAtlas K2Ve: Christian01 Garrison94 calls it the K0V anchor standard, but it appears to have been considered ~G8-G9 ubiquitously before MK43. Keenan80 lists it as one of the "stanard stars defining the zero point and scale for both temperature types and luminosity classes", and the only dwarf assigned this status between the Sun (K2V) and 61 Cyg A (K5V). However, more recently Gray03 placed it 1 subtype hotter (G9V), and it is a tad bluer (~0.79) than median B-V colors for field K0V dwarfs (~0.818-0.846, depending on sample). Apparently slightly metal poor [Fe/H]=-0.2 (see below). B-V(HIP)=0.786+-0.007, B-V=0.786+-0.007(Mermilliod91), V-I(HIP)=0.85+-0.02, U-B(Mermilliod91) = 0.386+-0.012. V(HIP)=4.67, V=4.678+-0.010(Mermilliod91), Ks(2MASS) = 2.900+-0.324(poor). PASTEL median values: = 5265 K, [Fe/H] ~ -0.2. Mv=5.87. plx = 173.2405 +- 0.2070mas(GaiaDR2). GaiaDR2: G=4.3838(raw), G=4.451(corrected), B and R do not require correction. G-V = 4.451 - 4.678 = -0.227+-0.011. Bp-Rp = 0.983, Bp-G = 0.430(corr), G-Rp = 0.553(cor). # Secondary Standard HD 224618 = LHS 552 = BD-17_6856 (J2359-1656) G6V: Adams35 *K0V: Roman55,Cowley67,Keenan80,Keenan83,Keenan85,McNiel86,Keenan88,Keenan89(stan) K2: Bidelman85 No published types since Keenan89. Nice agreement among Roman, Cowley, Keenan, but unfortunately it is very metal poor ([Fe/H] ~ -0.7), so its properties are probability not typical for field ~solar K0 dwarfs. B-V=0.785+-0.032 (HIP), B-V=0.773+-0.009(Mermilliod91), V=8.925+-0.008(Mermilliod91). PASTEL medians: = 5288K (N=2), logg=4.5+-0.2 (Tomkin99), [Fe/H]=-0.76+-0.06(Tomkin99), [Fe/H] = -0.59 (Casagrande11). plx = 27.7992 +- 0.1044mas(GaiaDR2). GaiaDR2 photometry does not to be corrected following Evans18: G= 8.698, Bp= 9.127, Rp= 8.140, (Bp-Rp)= 0.988, (Bp-G)= 0.430, (G-Rp)= 0.558. G-V = -0.227+-0.008. plx = 27.7992+-0.1044(GaiaDR2). Mv = 6.145+-0.011(M91,GaiaDR2), M_G = 5.918. # Tertiary Standard HD 284253 = Cl Melotte 25 21 = vB 21 = HIP 19934 = V984 Tau (J0416+2154) G7: Wilson48 G9V: Joy49 *K0V: Wilson62(K0),Morgan65,Corbally86(stan,Morgan65) Hyad, so [Fe/H] = +0.16(Liu16). BY Dra variable with variability ~0.04 mag (VSX). Active star logR'HK=-4.454 (Isaacson10), logLx/Lbol = -4.73(Wright11), Prot=10.26dq(Wright11). V=9.14(HIP), V=9.145+-0.005(Mermilliod91), B-V=0.814+-0.004(Mermilliod91), B-V=0.813+-0.002(HIP), U-B=0.467+-0.074(Mermilliod91). plx=19.5708+-0.0423mas(GaiaDR2) => Mv=5.603+-0.007(Mermilliod91,GaiaDR2). PASTEL: = 5360K(N=6), =4.50(N=4), [Fe/H]=+0.135(N=4). GaiaDR2: plx=19.5708+-0.0423mas, G=8.9230+-0.0004, E(BR/RP)=1.203, Bp-Rp=0.9786, Bp-G=0.4267, G-Rp=0.5519. M_G=5.381+-0.005, Mv=5.603+-0.007. G-V=8.9230 - 9.145 = -0.222. # Variant Standard HD 165341 = 70 Oph A = HR 6752 = GJ 702 = HIP 88601 A G8/K0V: Maury1897 *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). Boyajian12 reports tetLD=1.515+-0.005mas. plx=195.2166+-0.1012mas(GaiaDR2,for 70 OphB). Boyjian12+GaiaDR2 => Rad=0.834Rsun. Rad=0.831+-0.004Rsun(Yee17). PASTEL: =5258K(N=28), =4.52(N=19), <[Fe/H]>=+0.065(N=12). # 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 = LHS 23 = HIP 19849 (J0415-0739) G9V: Abt85 K0V: 1923LicOB..10..169L,Adams35,Wilson62,Morgan65,Keenan99 *K0.5V: Keenan88,GrayNstars(stan),Gray06 K1-V: Keenan83,Keenan85 K1V: Morgan37,Roman55,Bidelman85(K1),Gray03 Adopted K0.5V, so see entry in K0.5V.txt. 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). Mv=5.94. HD 124752 = HIP 69400 = BD+67_771 (J1412+6735) K0-V: Gray03 K0V: Cannon(K0),Roman49,JM53,Jaschek64(all) *K0.5V: Keenan80,Keenan83,Keenan85,Keenan88,Keenan89 K1V: Wilson50,LevatoAbt78 I've adopted this star as primary K0.5V standard, although it appeared as a K0V stanard in JohnsonMorgan53. The only star with multiple K0.5V classifications in Skiff MK compendium, both as standards for Keenan(1980,1989), but it appeared in all of the Keenan lists between 1980 and 1989 as K0.5V (although he did not put a dagger in front of it in his 1989 list, which signified "standard"). 5" binary with M2V star (Gray03). Ursa Major member? Surprisingly Gray03 placed it 0.75 subtype hotter, further suggesting that his types may be too hot around the G/K boundary compared to Keenan's standards. V=8.25(HIP), B-V=0.840+-0.005(HIP), V-I=0.88(HIP). [Fe/H] = 0.25(Marsakov88, photometric). Ursa Major stream member? (Schmitt90). plx = 25.3595+-0.0247mas(GaiaDR2) => Mv=5.27(HIP,GaiaDR2). 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. # Exemplars HD 10780 = HR 511 = HIP 8362 G5V: 1932MeUpp..55....1S G9V: Morgan37,Gray03 *K0V: 1927MeUpp..28....1L,Lindblad34,Adams35,Keenan41,Brodskaya60,Ljunggren61,Wilson62,Cowley67,Bidelman85(K0),BSC/Hoffleit91 K2V: JM53(non-stan,"dK2") Bewildering range of published types for a star that is supposedly roughly solar metallicity. Among "K0V" stars in Bright Star Catalog (Hoffleit91), this is the 4th brightest, but the brightest whose consensus type seems to be K0V *and* with near-solar metallicity. PASTEL: = 5350K(N=26), <[Fe/H]>=+0.03(N=17). V=5.63(HIP), V=5.631+-0.011(Mermilliod91), B-V=0.804+-0.010(HIP), B-V=0.804+-0.010(Mermilliod91), V-I=0.81(HIP). plx=99.5746+-0.0595mas(GaiaDR2) => Mv=5.622+-0.011(Mermilliod91,GaiaDR2). GaiaDR2: G=5.3827+-0.0012, E(BR/RP)=1.175, Bp-Rp=0.9652, Bp-G=0.4448, G-Rp=0.5204. HD 10780. G-V=5.3827-5.631=-0.2483. HD 149661 = 12 Oph = HR 6171 = GJ 631 = HIP 81300 = V2133 Oph *K0V: Adams35,Wilson62,Bidelman85(K0),Gray03,Gray06(K0V(k)) K1V: Houk99 K2V: Cowley67 Nearby young, active K0 dwarf of approximately solar composition. 6th brightest K0V star in Bright Star Catalog(Hoffleit91). BY Dra variable with amplitude 0.04 mag (VSX), chromospherically active (logR'HK = -4.583; age ~ 1.0-1.9 Gyr; Mamajek08). V=5.764+-0.017(Mermilliod91), V=5.77(HIP), V=5.75(BSC), V=5.74(Johnson66), B-V=0.827+-0.012(Mermilliod91,HIP), B-V=0.81(Johnson66), U-B = 0.492+-0.027(Mermilliod91), U-B=0.45(Johnson66), V-I=0.87+-0.02(HIP). plx = 100.8111+-0.0788mas(GaiaDR2), plx=102.55+-0.40mas(HIP2). Mv = 5.782+-0.017(M91,GaiaDR2). G=5.5300+-0.0008, Bp-Rp=1.0102, Bp-G=0.4552, G-Rp=0.5550 => corrected via Evans18 (only G needs correcting) => G=5.551, Bp-Rp=1.010, Bp-G=0.434, G-Rp=0.576. G-V = 5.551 - 5.764 = -0.213. PASTEL medians: = 5264K(N=24), = 4.55(N=20), <[Fe/H]> = 0.05(N=15). Boyajian12 measured limb darkened diameter tet_LD = 0.724+-0.011 mas and fbol = (14.160+-0.090)e-8 erg/s/cm2 => IAU2015 mbol = 5.625+-0.007 => BCv = mbol - V = 5.625 - 5.764 = -0.139+-0.018. Mass = 0.84 Msun(Ramirez12). plx=100.8111+-0.0788mas (GaiaDR2). Boyajian12 diam & GaiaDR2 dist => 0.772Rsun. R=0.759+-0.012Rsun(Yee17). 55 Cnc = rho01 Cnc = HR 3522 = HD 75732 = GJ 324 G8V: Cowley67 K0V: 1927MeUpp..28....1L,Adams35,Greenstein68(CN,C2 strong) K0: Bidelman85 *K0IV-V: Gray03 K0IV: Hagen67 K2V: Lindblad34 Generally good agreement on K0 type, but very metal-rich. Very well-characterized exoplanet host (vonBraun11). vonBraun11 estimates age 10.2+-2.5 Gyr from isochrones, although Marcy02 listed 3-8 Gyr. Greenstein68 pointed it out as a strong metallic-line star found to contain enhanced CN, C2, and CH. PASTEL compendium has 42 entries: Teff=5270 (N=41), logg=4.40 (N=33), [Fe/H]=+0.34 (N=33). vonBraun11: Teff=5196+-24K, fbol=(.1227+-0.0177)e-7 erg/s/cm2 (=> mbol = 5.780+-0.016 mag; IAU2015 scale; BCv = V - mbol = 5.780 - 5.944 = -0.164), L=0.582+-0.014 Lsun. For SED template fit, they averaged G8IV and K0IV to produce a 'G9IV'. Mermilliod91: V=5.944+-0.020, B-V=0.860+-0.010, U-B=0.648+-0.010. plx=79.4274+-0.0777mas(GaiaDR2). Mv=5.444+-0.020. Rotation: 35-42d (Marcy02), 37.4+-0.5d(Mittag17). GaiaDR2: G=5.7144+-0.0006, E(BR/RP)=1.193, Bp-Rp=1.0135, Bp-G=0.4570, G-Rp=0.5565. G-V = 5.7144 - 5.944 = -0.2296. 20 Crt = HR 4458 = HIP 56452 = LHS 308 = LDS 6245 = WDS J11345-3250 K0-V: Gray06 *K0V: Evans57,Wilson62,Houk82,Bidelman85(K0),Reid95 K2V: Adams35 16" binary with V=14.9 DC8 white dwarf (LHS 309). V=5.96(HIP), V=5.964+-0.007(Mermilliodd91), B-V=0.813+-0.007(Mermilliod91), B-V=0.811+-0.007(HIP), U-B=0.342+-0.015(Mermilliod91). Ks=4.022+-0.036(2MASS,qual=E). PASTEL: = 5165K(N=9), =4.585(N=8), <[Fe/H]> = -0.38(N=8). GaiaDR2: plx=104.7828+-0.0518mas, G=5.7194+-0.0005, E(BR/RP)=1.189, Bp-Rp=1.0025, Bp-G=0.4532, G-Rp=0.5492. Mv=6.065+-0.007, M_G=5.821+-0.001, G-V = 5.7194 - 5.964 = -0.245. # Other Stars Morgan65 classified three Hyads as K0V: HD 284253 (B-V=0.813), HD 285773 (B-V=0.831), HD 28258 (B-V=0.839). Median = 0.831. RECONS list shows GJ 702A (70 Oph A; J1805+0230) as the nearest K0V star. HD 100623 = HR 4458 *K0-V: Gray06 K0V: Evans57,Wilson62,Houk82,Bidelman85(K0) K2V: Adams35 Somewhat metal-poor ([Fe/H] ~ -0.4) star with White dwarf companion 16" away (DC/DQ; Henry02). 9th brightest K0V star in Bright Star Catalog(Hoffleit91). V=5.964+-0.007(Mermilliod91), B-V=0.813+-0.007(Mermilliod91), U-B=0.342+-0.015(Mermillid91). PASTEL published values: = 5208K(N=8), <[Fe/H]> = -0.39(N=6), = 4.61(N=6). HR 173 = HD 3795 = HIP 3185 = GJ 9019 = GJ 27.2 = LHS 1124 G0V: 1966ArA.....3..501L G3V: Adams35 G3/5V: Houk88 G6: Bidelman85 *K0V_Fe-1.5_CH-1.3: Gray06 11 Gyr-old thick disk star in solar neighborhood (d=28.4pc; plx=35.1312 +-0.1452mas; GaiaDR2). Listed here because I noticed it was the coolest star in CASTUP sample (FGK d<30pc) with logg<4.1 and clearly not typical MS or slightly pre-MS (like AB Dor). Next hotter star that fulfills this criterion was 70 Vir (old thin disk star; e.g. Fuhrmann17). PASTEL: = 5377K(N=16), =3.89(N=9), <[Fe/H]>=-0.59(N=14). Ramirez13 estimates probability 96% thick disk membership (1% thin, 3% halo). Soubiran05 estimates 100% thick disk membership. Alpha-enriched: [Si/Fe]=0.22(Soubiran05), [Mg/Fe]=0.31(Soubiran05), [alpha/Fe]=0.26(Soubiran05). Age: 11.15(10.79-11.71)Gyr(Ramirez12), 11.8(+-10%)Gyr(Soubiran05). HD 136442 = HR 5706 K0V: Popper43(Hoffleit91) K1: Bidelman85 *K2III: Luck17 K2: Cannon 11th brightest "K0V" star in Bright Star Catalog(Hoffleit91), but appears to be a metal-rich giant. PASTEL: = 4880K(N=3), =3.35(N=3), <[Fe/H]>=+0.40(N=3). HD 153226 = HR 6301 = HIP 82989 *K0IV: Halliday55 K0V: Harlan69(Hoffleit91) 13th brightest "K0V" star in Bright Star Catalog(Hoffleit91), but appears to be a giant. PASTEL: = 4955K(N=3), logg=3.37(N=3), [Fe/H]=+0.03(N=3). ### Notes - Closer look at the G/K Boundary (Trying to pin down "K0V") 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 bright nearby standards that were adopted early on (e.g. tau Cet, HD 224618, sig Dra, omi^2 Eri). The approximately solar metallicity standards are well established: 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] ### Mapping of Houk/Michigan Spectral Survey Types to Modern MK Grid (Gray/Keenan) for K Dwarfs See section 4.1 of Pecaut & Mamajek (2016) for a discussion on the subtle differences between specral classifications for dwarfs between the Michigan Spectral Survey catalog (Houk et al.) and those classified by Gray and collaborators on the modern MK grid (MK78 for hot stars through late F, Keenan standards for late F through M): https://ui.adsabs.harvard.edu/abs/2016MNRAS.461..794P/abstract). For the K dwarfs, PecautMamajek16 estimate the following mapping of types: SpT(Houk) SpT(Gray) G8V => G8.5V K0V => K0V K0/1V => K1V K1V => K1.5V K1/2V => K2V K2V => K2.5V K2/3V => K3V K3V => K3V K3/4V => K4V K4V => K4+V K4/5V => K5V K5V => K6-V K5/M0V => K7V M0V => K6.5V ### 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 ### Ranges on parameters for K dwarfs Among a compilation of 92 nearby K dwarfs within 25 pc with published Teff and luminosity estimates with uncertainties