AA2V Garrison94 doe not list an A2V anchor standard, and MK73 does not list a A2V dagger standard. Gray87 lists two A2V standards: HD 88955 (A2Va) and HD 56405 (A2Van), which are probably the best available. Similar to A1V where the standards have migrated considerably over the years. A case where MK43 listed some A2V standards, then JM53 ignored them and listed two more, then MK78 listed a completely different star, and then Gray87 listed two new stars all together. Considering the inconsistency of the A2V standards, it seems amazing that at least one star (iot Cen = HD 115892) has remained an A2 from Cannon until Garrison in the 1990s. So at least generations of astronomers agree upon at least *one* star as being an A2 dwarf. MK43 standard: eta Oph - A2V zet UMa A (Mizar A) - A2V JM53 standard: tet And - A2V tet Leo - A2V Cowley69 standards: tet And - A2V tet Leo - A2V zet UMa - A2V 26 UMa - A2V MK78 standard: HD 23948 (= Cl Melotte 22 2488 = Hz I 996) - A2V Garrison79 standard: tet Leo - A2V Keenan85 standard: HD 23948 - A2V Gray87 standards: HD 88955 - A2Va HD 56405 - A2Van Gray87 claims that the MK A2 is really halfway between A0 and A3 daggers, so they shuffle the early As a bit. Skiff08 flagged HD 23948 (MK78) as the only A2V standard. Mean B-V[A2V] = 0.061, hence again Iot Cen seems representative of the type Gray01/03/06 list 5 nearby A2Vs. Their median HIP colors: For A2V Hipparcos stars within 75pc, with parallax S/N > 8, and within 1 mag of the MS (N=16): (A2V) = 0.179 (+-0.038 sem, +-0.134 stdev; N=16) (A2V) = 0.179 (+-0.028 sem, +-0.155 stdev; N=16) (A2V) = 0.202 (+-0.035 sem, +-0.165 stdev; N=16) (A2V) = 0.088 (+-0.026 sem, +-0.085 stdev; N=16) (A2V) = 0.094 (+-0.023 sem, +-0.064 stdev; N=16) (A2V) = 0.101 (+-0.029 sem, +-0.064 stdev; N=16) (A2V) =-0.010 (+-0.002 sem, +-0.010 stdev; N=16) (A2V) = 0.189 (+-0.057 sem, +-0.160 stdev; N=16) (B-V)(A2V) = 0.118 ; BakisEker22 (B-V)(A2V) = 0.091 ; exemplar gam Cet (unresolved) (B-V)(A2V) = 0.083 ; exemplar eps Gru (B-V)(A2V) = 0.079 ; pri. stan. HD 56405 (A2V) = 0.077 (+-0.017 sem, +-0.042 stdev) ; HIP d<75 S/N>8 N=16) (A2V) = 0.075 (+-0.019 sem, +-0.036 stdev) ; Gray01/03/06 N=5) (B-V)(A2V) = 0.069 ; d<60 pc SIMBAD A2V N=14 (B-V)(A2V) = 0.068 ; smoothed trend SpT vs (B-V)o B9.5V-F3V 11/2021 (B-V)(A2V) = 0.068 ; exemplar iota Cen (B-V)(A2V) = 0.06 ; Morgan53, Johnson63, Johnson66, Morgan71, KenyonHartmann95 (B-V)(A2V) = 0.055 ; Bessell79 (B-V)(A2V) = 0.051 ; pri. stan. HD 88955 (B-V)(A2V) = 0.05 ; Fitzgerald70 (B-V)(A2V) = 0.05 ; Schmidt-Kaler82 (B-V)(A2V) = 0.04 ; Garrison67 => adopt (B-V)(A2V) = 0.07 *** [last updated 11/21/2021] => adopt (U-B)(A2V) = 0.060 => adopt (V-I)(A2V) = 0.086 => adopt (V-R)(A2V) = 0.039 => adopt (R-I)(A2V) = 0.047 => adopt (V-J)(A2V) = 0.156 => adopt (V-H)(A2V) = 0.144 => adopt (V-Ks)(A2V) = 0.178 => adopt (H-Ks)(A2V) = 0.034 => adopt (J-H)(A2V) = -0.012 (Bp-Rp)(A2V) = 0.101 ; Evans18 trend for V-I= 0.086 (Bp-Rp)(A2V) = 0.068 ; color trend for B-V=0.07 => adopt (Bp-Rp)(A2V) = 0.068 [updated 11/22/2020] (Bp-G)(A2V) = 0.013 ; color trend for B-V=0.07 => adopt (Bp-G)(A2V) = 0.013 [updated 11/22/2020] (G-Rp)(A2V) = 0.050 ; color trend for B-V=0.07 => adopt (G-Rp)(A2V) = 0.050 [updated 11/22/2020] (Ks-W1)(A2V) = 0.044 ; EEM trend for d<30pc for B-V=0.07 => adopt (Ks-W1)(A2V) = 0.044 [updated 12/29/2019] (G-V)(A2V) = -0.075 ; * b03 Cyg dS* A2V (G-V)(A2V) = -0.025 ; polynomial fit for f(B-V) (G-V)(A2V) = -0.023 ; * del02 Tau PM* A2Vs (G-V)(A2V) = -0.023 ; * kap Psc a2* A2VpSrCrSi (G-V)(A2V) = -0.022 ; * nu. Hor PM* A2V (G-V)(A2V) = -0.010 ; * 82 UMa PM* A2Vnp (G-V)(A2V) = -0.006 ; * del Hyi PM* A2V (G-V)(A2V) = -0.005 ; * gam Cet A A2Vn (G-V)(A2V) = 0.000 ; * 36 Cyg * A2V (G-V)(A2V) = 0.003 ; HD 19275 PM* A2Vnn (G-V)(A2V) = 0.008 ; * 26 Gem PM* A2V (G-V)(A2V) = 0.010 ; fit for A dwarfs from Kervella19 corrected for E(B-V), eval for (V-Ks)=0.178 (G-V)(A2V) = 0.013 ; * 50 Cas * A2V (G-V)(A2V) = 0.014 ; * del UMa PM* A2Vn => adopt (G-V)(A2V) = 0.00 [updated 4/8/2022] (U-B)(A2V) = 0.06 ; Johnson66 (U-B)(A2V) = 0.05 ; Fitzgerald70 (U-B)(A2V) = 0.048 ; HIP d<75pc S/N>8 A2V N=43 (Mermilliod91 photometry) (A2V) = 0.048 (+-0.028 sem, +-0.055 stdev) ; Gray01/03/06 N=5) (V-I)(A2V) = 0.072 ; Bessell79 (A2V) = 0.091 (+-0.016 sem, +-0.043 stdev) ; Gray01/03/06 N=16) (R-I)(A2V) = 0.072 ; Bessell79 (g-r)(A2V) = -0.044 ; Jordi06 (V-R)=>(g-r) for V-R=0.039 (g-r)(A2V) = -0.173 ; Bilir05 (B-V)=>(g-r) for B-V=0.070 (g-r)(A2V) = -0.23 ; Covey07 => adopt (g-r)(A2V) = -0.17 [updated 10/10/2020] Teff(A2V) = 9000 K ; Bessell79 Teff(A2V) = 8995 K ; Zorec12 median Teff(A2V) = 8990 K ; Theodossiou90 Teff(A2V) = 8990 K ; GrayCorbally94 Teff(A2V) = 8970 K ; Schmidt-Kaler82 Teff(A2V) = 8900 K ; GrayCorbally09 Teff(A2V) = 8890 K ; pri. stan. HD 88955 Teff(A2V) = 8836 K ; EEM N=150 Teffs Teff(A2V) = 8755 K ; pri. stan. HD 56405 Teff(A2V) = 8720 K ; mean photometric Teff Teff(A2V) = 8613 K ; exemplar HD 106591 (del UMa) Teff(A2V) = 8597 K ; exemplar gam Cet A Teff(A2V) = 8548 K ; Boyajian12 Teff(A2V) = 8511 K ; exemplar HD 215789 (eps Gru) => adopt Teff(A2V) = 8800 K (logT = 3.944) [updated 9/16/2019] BCv(A2V) = -0.112 mag ; Flower96(Teff=8800K, set so BCv(5772K)=-0.085 BCv(A2V) = -0.070 mag ; Schmidt-Kaler82 (BCv=-0.20 + 0.13 offset) BCv(A2V) = -0.066 mag ; Code76(Teff=8800K, set so BCv(5772K)=-0.085) BCv(A2V) = -0.069 mag ; Balona94(Teff=8800K, set so BCv(5772K)=-0.085 BCv(A2V) = -0.056 mag ; Bessell98(ATLAS9,logg=4.5,Teff=8800K, set so BCv(5772K)=-0.085 BCv(A2V) = -0.032 mag ; Bertone04(ATLAS,Teff=8800K, set so BCv(5772K)=-0.085) => adopt BCv(A2V) = -0.07 [updated 9/16/2019; set so that BCv(5772K)=-0.085] Mv(A2V) = 1.9 mag ; GrayCorbally09 Mv(A2V) = 1.59 mag ; d<60 pc SIMBAD A2V N=12 Mv(A2V) = 1.58 mag ; exemplar gam Cet A = HR 4660 = HD 106591 Mv(A2V) = 1.50 mag ; B/A/F dwarf sequence for B-V=0.07 Mv(A2V) = 1.46 mag ; Wright05(B-V=0.07) Mv(A2V) = 1.43 +-0.08 sem, +-0.51 st.dev. ; EEM N=44 HIP A2V d<75pc Mv(A2V) = 1.39 mag ; pri. stan. HD 88955 = HR 4023 Mv(A2V) = 1.38 mag ; d<60pc Mv(B-V=0.07) Mv(A2V) = 1.36 mag ; exemplar HD 106591 = del UMa Mv(A2V) = 1.35 mag ; linear B-V vs. Mv fit to d<50pc Gray01/03/06 dwarfs for B-V=0.07 Mv(A2V) = 1.32 mag ; median Mv for A2V calc using Kervella19 HIP & Gaia DR2 (d<100pc) Mv(A2V) = 1.3 mag ; Schmidt-Kaler82 Mv(A2V) = 1.00 mag ; Wegner07 Mv(A2V) = 0.88 mag ; pri. stan. HD 56405 = HR 2758 Mv(A2V) = 0.51 mag ; exemplar eps Gru = HR 8675 => adopt Mv(A2V) = 1.35 mag [updated 9/26/2020] => adopt M_G(A2V) = 1.345 mag [updated 12/10/2020] (Mv=1.35, G-V=-0.005) => adopt M_Ks(A2V) = 1.172 mag [updated 12/30/2020] (Mv=1.35, V-Ks=0.178) logL(A2V) = 1.324 dex ; Mv=1.50 + BCv=-0.07 => Mbol = 1.430 logL(A2V) = 1.384 dex ; Mv=1.35, BCv=-0.07 => Mbol = 1.28 logL(A2V) = 1.66 dex ; sec. stan. HD 56405 (Zorec12) logL(A2V) = 1.75 dex ; Zorec12 median => adopt logL(A2V) = 1.384 dex [updated 9/26/2020] => adopt Mbol(A2V) = 1.280 mag [updated 9/26/2020] Mass(A2V) = 2.48 Msun ; Zorec12 median Mass(A2V) = 2.37 Msun ; sec. stan. HD 56405 (Zorec12) Mass(A2V) = 2.324+-0.045 Msun ; Eclipsing binary WX Cep B (Torres10) Mass(A2V) = 2.06 Msun ; EEM Mv vs. Mass fit for binaries (Mv=1.5) Mass(A2V) = 2.07 Msun ; EEM Teff vs. Mass fit for binaries (Teff=8760K) Mass(A2V) = 2.02 Msun ; EEM logL vs. Mass fit for binaries (logL=1.324) Mass(A2V) = 2.01 Msun ; Ekers18 ML calibration for logL=1.324 Mass(A2V) = 1.98 Msun ; HenryMcCarthy93 calibration for Mv=1.5 Mass(A2V) = 1.904+-0.013 Msun ; Eclipsing binary V392 Car A (Torres10) Mass(A2V) = 1.855+-0.020 Msun ; Eclipsing binary V392 Car B (Torres10) => adopt Mass(A2V) = 2.05 Msun [updated 12/29/2019] Rad(A2V) = 2.1168 Rsun ; logL=1.384, Teff=8800K Rad(A2V) = 1.976 Rsun ; logL=1.324,Teff=8800K => adopt Rad(A2V) = 2.117 Rsun [updated 9/26/2020] # No Standard Morgan65, Houk75, MK73, GrayAtlas, and GrayNstars do not list a A2V standard # Primary Standards HD 88955 = HR 4023 A2V: Gray87(stan),Cannon(A2),Levato72,deVauc57 *A2Va: Gray06 A1V: Houk78(overexp,from Garrison) All the Skiff07 types are "A2V" or "A2Va". Probably good standard. HIP: B-V=0.051+-0.005. Mermilliod91: V=3.844+-0.005, B-V=0.054+-0.005, U-B=0.068+-0.013. Teffs: 8629K(GaiaDR2), 8829K(Gray06), 8890K(Sokolov95,Stassun18), 8953K(Erspamer03), 9451K(David15) => = 8890K. logg=4.13(Erspamer03), 4.14(Gray06). [Fe/H]=0.06(Erspamer03), 0.02(Gray06). vsini=103 km/s(Erspamer03). Mv=1.39. HD 56405 = HR 2758 = HIP 35180 (in NGC 2477?) *A2Van: GrayGarrison87 A2V: Abt95 A2Vnp: Hoffleit91(BSC) A2: Cannon A3V: Jaschek78(Cowley69) A1V: Houk88 parallax: 12.12+-0.40 mas(vanLeeuwen07). HIP: B-V=0.079+-0.005, V-Ic=0.09+-0.01. Mermilliod91: V=5.452+-0.009, B-V=0.081+-0.006, U-B=0.050+-0.010. Teffs: 8627K(B-V=>Bessell98,logg=4.0), 8702+-219K(Paunzen06), 8721+-87K(Blackwell98), 8755K(Stassun18), 8842K(GaiaDR2), 8872K(Zorec12), 9562K(David15), => = 8755K. vsini = 154 km/s(Paunzen06), 159km/s(Zorec12). logg=3.91+-0.12(Allende-Prieto99). logL=1.6631+-0.0328(Zorec12). Mass=2.13+-0.14Msun(Allende-Prieto99), 2.37+-0.04Msun(Zorec12). Age = 748+-38 Myr(Zorec12). Mv=0.88. # Exemplars HD 106591 = del UMa = HR 4660 A3V: MK43, Jaschek64(all),Jaschek78(JM53) *A2Vn: Cannon20(A2),Palmer68(A2Vn),Cucchiaro78(A2V),Levato78(A2V),GrayGarrison87(A2Van),Abt95,Gray03 Skiff MK compendium notes states that 1920AnHar..95.....C listed del UMa as the HD standard for type A2, although it later appeared as a A3V standard in MK43. Migrated from A3V (MK/JM53) to A2V (Gray/Garrison/Abt) - probably not good standard. All published types after MK43 are A2V or variant. Teffs: 7517K(Bermejo13), 8564K(Wu11), 8595K(Malkin02), 8600K(Gebran16), 8613K(Gray03), 8670K(Zorec12,Stassun18), 8707K(King03), 8750K(Chen14), 9757K(David15) => = 8613K. Mv=1.36. eps Gru = HR 8675 = HD 215789 = HIP 112623 *A2V: Cannon(A2),Devaocouleurs57,Garrison96(A2Va),GrayGarrison87(A2Va),Abt95(A2Vn) A2IVn: Gray06(SB) A3V: 1955MmMtS..12....1W,Levato72(A3Vn),Houk78(from Garrison) plx = 25.30+-0.48mas(GaiaDR2), plx=24.1070+-0.2887mas(GaiaDR2). V=3.49(HIP), V=3.480+-0.007(Mermilliod91), B-V=0.083+-0.007(HIP), B-V=0.082+-0.004(Mermilliod91), V-Ic=0.10+-0.02(HIP). Teffs: 7900K(Sokolov95,Stassun18), 8137K(Gray06), 8511K(AllendePrieto99), 8625K(Ammler-vonEiff12), 8685K(David15), => = 8511K. Mv=0.51. gam Cet A = Kaffaljidhma = HR 4660 = HIP 59774 = HD 106591 = GJ 459 = WDS J12154+5702A A1V: Bidelman85(A1),Abt85 A1/2V: Maury1897 *A2Vn: Adams35,Chalonge52(A2V),Slettebak54(A2V),1955MmMtS..12....1W(A2V),GrayGarrison87(A2Va),Abt95,Gray03 A3V: Roman49,Cowley69,Levato78,Cucchiaro78 Unresolved: V=3.464+-0.009(Mermilliod91), B-V= 0.091+-0.006(Mermilliod91), U-B=0.070+-0.008(Mermilliod91). WDS reports delta(mag) = 2.64, with V(A)=3.54, V(B) = 6.18. C component is 843" away. Teffs: 7470K(Bermejo13), 8360K(Sokolov95), 8455K(Paunzen06), 8551K(David15), 8643K(Stassun18), 8673K(Gray03), 9057K(Zorec12), 9296K(King03) => = 8597K. plx=40.51+-0.15mas (vanLeeuwen07). Mv = 1.58(V(A)=3.54,plx(vanLeeuwen07)). # Other stars HD 115892 = iot Cen (B-V[HIP] = 0.068+-0.004) A2V: Cannon18(A2),deVauc57,Levato72,Jaschek78,Houk82,Gray87(Va),Garrison96(A2Va) *kA1.5hA3mA3Va: Gray06 All of the spectral types (in Skiff07 and otherwise) for this object *were* "A2", until Gray06. Keenan63 (in "Basic Astronomical Data" ed. Strand) lists iot Cen as one of two "typical" A2 stars (along with S CMa). So if the Ca H & K features are not typical for A2 (or intermediate between higher pedigree A1V and A3V standards), then presumably Gray06's classification suggests that this may not make a good A2V standard. However, Gaspar16 lists a very solar-ish [Fe/H]=-0.07+-0.05, although Gray06 lists a super-solar [M/H]=0.32. plx=55.49+-0.17 mas(HIP2), so nearby and unreddened. HIP: B-V = 0.068+-0.004, V-Ic = 0.02+-0.02, V = 2.75. Mermilliod91: V=2.751+-0.014, B-V=0.044+-0.009, U-B=0.031+-0.020. All 2MASS photometry for this star is of poor quality. Teffs: 9061K(B-V=>Bessell98,logg=4.1), 9102+-82K(Blackwell98), 9164K(Philip80), 9308K(diBenedetto98), 10207K(Gray06) => median Teff = 9164K. logg=4.06(Gray06), 4.19(Philip80). [M/H]=0.32(Gray06). HRD position: V=2.751, BCv=-0.07, plx=55.49, Av=0 => Mv=1.472, Mbol=1.402, logL=1.335. w/Teff=9164K => Rad=1.845 Rsun. # Deprecated Standards HD 155125 = eta Oph A2V: MK43,Jaschek64(most),Cowley69,Cannon(A2) *A2Va+((Sr)): GrayGarrison87(non-stan) A2IVs: Abt81 A2IV: Abt95 A2.5VA: Houk88 A1V+A3V: Edwards76 0.4" tight binary. HD 23948 = Cl Melotte 22 2488 *A1Va: GrayGarrison87 A2V: MK78,Keenan85 Arg. Standard, standard, no. Deprecated as A2V standard due to Gray & Garrison's reclassification. HD 97633 = tet Leo = 70 Leo = HR 4359 A2V: JM53,Cowley69(stan),Garrison79(stan) *A2IV(k var): GrayGarrison87 zet Lep *A2Vann: Cannon(A2),Houk88(Garrison),Garrison96,GrayGarrison87(A2Van) A3V: Slettebak54,Jaschek64(most),Jaschek78(A3Vn,Cowley69),Abt95(A3Vn) Jaschek64 shows 9 A3V refs and 1 A2IV ref. Split A2V and A3V - inappropriate as candidate standard HD 1280 = tet And = 24 And = HR 63 A2V: Cannon(A2),JM53,Jaschek64(all),Cowley69(stan),Jaschek78(JM53),Garcia89,Hoffleit91 *A2IV: GrayGarrison87(A2IV-),Abt95 Good agreement on subtype. 1.25 mag above main sequence, so probably IV. HR 2534 A2:V:kn((SrII)) : MK78 Why is a star with colons after the subtypes listed as a "standard"? HD 82621 = 26 UMa = HR 3799 = HIP 47006 A0: Cannon A0Vn: Abt95 *A1Va: GrayGarrison87 A2V: Slettebak54,Jaschek64(all),Cowley69(stan),Jaschek78(Morgan53), Was A2V under Morgan, but has moved to A0/A1 by Gray/Garrison and Abt. HD 116656 = zet UMa = Mizar A2V: MK43,Cowley69(stan) A1VpSrSi: Abt81 *A1.5Vas: Gray03 A1Va+((Si)): Gray87 Quadruple. Probably not standard material. Gray87 and Gray03 types don't agree. MK43 lists "Zeta UMa br." as the A2V standard. HD 6288 A = HR 301 A = HI 4979 = 26 Cet A2V: Abt68 A8IV: Houk99 A8V: Wilson50 F1V: Cowley74,Abt95 A7III:: Cowley76 F0: Cannon F0V: Adams35 Strange case. Abt68 showed "HR 301A" as an A2V star, but it is much later in all other publications, including being listed as F1V in Abt95! This must be a typo? Houk notes: "HR 301; 26 CET; UNDETECTED VISUAL DOUBLE p=254°d=16.0arcsec MAGS 6.11, 9.52". Not a good standard.