A2III

The best A2III standard (southernly accessible also) is HR 2751

GrayGarrison87 standard: HR 2751 (=HD 56169) - A2III(high vsini)

(J-H)(A2III)  = 0.027 ; smoothed relation from giants in Skiff compnedium w/i 15 deg of NGP, 2MASS photometry AAA flags
(H-Ks)(A2III) = 0.021 ; smoothed relation from giants in Skiff compnedium w/i 15 deg of NGP, 2MASS photometry AAA flags
=> adopt (J-H)(A2III)  = 0.027 [updated 10/30/2020]
=> adopt (H-Ks)(A2III) = 0.021 [updated 10/30/2020]


# No standard

GrayGarrison87 list a high vsini A2IIIn standard, but no low vsini
A2III standard. MK43, JM53, Cowley69, and Houk do not list a A2III standard.

# Primary standard

HD 56169 = HR 2751
  *A2IIIn: GrayGarrison87(high vsini stan.)
   A3Vn: Abt95
   A3III-IV: Slettebak54
   A4IIIn: Cowley69

   "A2IIIn" standard for GrayGarrison87, but not considered "A2" type
   by others.

# Other stars (candidate standards?)

HD 169981 (J1825+2949; V=5.8)
   Three published A2III types

HD 42111 = HR 2174 (J0608+0229; V=5.7)
   multiple A2III published types, another shell star (see Skiff10 catalog)

HD 75710 (J0849-4518 ; V=4.9)
   multiple A2III published types (Houk & GarrisonGray87)

HD 30823 = HR 1550 (J0452+4235; V=5.7)
  *A2IIIn shell: GrayGarrison87
   A2III: Appenzeller67,Davis77
   A1IVn shell: Abt95
   A3III: Cowley69

   Only star in Skiff10 compendium with 3 or more "modern" published
   "A2III" (or variant) types, but apparently a "shell" star.

HD 187340 = HR 7545 = HIP 97122 (J1944+6920; V=5.9)
   A2III: Cowley69, Hoffleit91(BSC), Abt95
  *A2.5IV: GrayGarrison87
   A3V: 

   In Indo-US survey (Valdes04).