view Abstract Citations (17) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Temperature classification of the S-type stars. Keenan, Philip C. Abstract The use of band intensities to arrange the S- type stars in a temperature sequence is suggested by these observed relations between spectra of types M and S: (I) Stars can be found representing every step in the transition from pure type M (TrO strong, negligible ZrO), through various mixtures of the bands of the two molecules, to the extreme type S (ZrO strong, negligible PrO). (2) PrO bands strengthen with diminishing temperature and form the criteria of classification within type M. A similar temperature dependence of the ZrO bands is indicated by their strengthening with decreasing light in long- period variables. (3) The greatest strengths of bands of ZrO and PiO do not occur in the same stars. Bands of the two molecules seem to inhibit each other as they would if a fixed amount of oxygen were being divided among the metals. The proposed classification uses a weighted sum of the ZrO and TiO bands in assigning subclasses in the temperature sequence running from So to S9 or later. In order to include a measure of the relative strength of ZrO to PrO (which was the basis of Miss Davis' provisional classification), the drfrerence between the ZrO and PrO bands is used in assigning subscripts to the main types. Thus a cool star very strong in ZrO would be called 57,, while if ZrO were extremely weak the type would be S7o = M7. Preliminary types for a few well-known stars follow: HD 121447 So S UMa (Max) 51, R Gem (Max) S2~ R Gem (Ft. Max) 55, V679 Oph S35 HR 1105 S4~ R Cyg (Max) S37 R Cyg (9",7) S87 HD 177175 S5a The three stars R CMi, W Cas, and R Ori, which do not show bands of ZrO have generally been assigned to type S because of similarity in the strengths of some of the atomic lines. W. B. Bidelman at Yerkes and the author find strong infra-red bands of CX and several of the Swan bands of C1 in R CMi and W Cas. Since Vyssotsky had previously reported the blue CX bands as very strong in R Ori,' it appears that these three stars should be removed from type S and grouped with the red carbon stars. I.Unpublished. Reported at Tonanzintla Symposium in 1942. Perkins Observatory, Ohio Wesleyan University, Delaware, Ohio. Publication: The Astronomical Journal Pub Date: 1950 DOI: 10.1086/106450 Bibcode: 1950AJ.....55R.172K full text sources ADS | data products SIMBAD (7)