The spectrum of HR 4049 = HD 89353. This spectrum is under investigation by Helmut Abt; I am indebted to Dr. Abt for permission to include the following observations.
The only lines visible on 39 Å/mm plates in the range 3900-4900 are rather narrow H lines and a weak Ca II K line. Abt has assigned a type of A0 Ib-II, with marked peculiarities. The He I lines at 4026 and 4471 (which are easily visible in the A0 Ib standard Leo - and are strong in the B7 III standard Tau) are absent; also absent are the strong lines of Fe II and Mg II, which are outstanding in Leo. On a coudé spectrogram, the K line is resolved into two components: one stellar and one apparently interstellar. The spectrum of HR 4049 is illustrated in figures 1 and 2 [plates 1 and 2] from Dr. Abt's spectrograms.
It can be seen from the above that there is no MK box that can accept the spectrum of HR 4049 satisfactorily; the line weakening is pronounced.
The spectrum of HD 22879. This spectrum is reproduced in the Morgan-Abt-Tapscott Revised MK Spectral Atlas for Stars Earlier than the Sun; it is in plate 31 therein.
Here, we have a smaller degree of line weakening than in the case of HR 4049; however, it is great enough to bar satisfactory classification in any box of the MK System.