CN Features Research Articles

The Spectral Classification of Southern Carbon Stars

Well-widened objective prism spectra of carbon stars south of −25° declination have been examined to determine their suitability for classification. These spectra, taken by Henize in the early 1950's from South Africa as part of the Michigan-Mt. Wilson Hα survey of the southern sky, have a reciprocal dispersion at Na I 5890 Å of 300 Å mm−1 and are in good focus in the range between 5100 and 6600 Å.Compared with spectra of northern carbon stars taken by the writer at the Lindheimer Astronomical Research Center with the one meter reflecting telescope and Cassegrain spectrograph at a grating reciprocal dispersion of 263 Å mm-1, and compared with spectra taken by Sanford of carbon stars overlapping the Henize sample, the objective prism spectra have been found of sufficient quality to support their classification into five groups following the scheme as proposed by Keenan and Morgan in 1941 and as refined by Gordon in 1967.The first group exhibit weak C2 and CN features and Hα in absorption; the second, features attributable to a low C12/C13 ratio; the third, strong C2 and CN features and only moderately strong Na i in absorption; the fourth, very strong Na i in absorption; and the fifth, Hα in emission. Examples are given of each group, stars not fitting well into any of these groups are discussed, and the significance of each group is mentioned in light of work by Bouigue, Gordon, Peery, and Richer.

The Synthetic Spectrum of the CN Red System and its Application to Stellar Spectra of Moderate Resolution

view Abstract Citations (8) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Synthetic Spectrum of the CN Red System and its Application to Stellar Spectra of Moderate Resolution Marenin, Irene ; Greene, Arthur E. Abstract Assuming a Milne-Eddington model atmosphere, we have calculated synthetic spectra for the CN red system from A5600 to A6800. The spectra were calculated for a pure 12C14N spectrum and a CN spectrum with a 12C113C = 4. They were then compared to the spectra of several S, SC, and C stars. Several conclusions can be drawn: (1) CN features are observed at all wavelengths with no obvious windows. (2) The CN features are weakest between AA6l00 and 6120 and longward of A6810. (3) The addition of 13C14N smoothes out the spectrum so that all bands are not very pronounced. (4) CN causes major problems in detecting traces of ZrO and C2 in the red spectral region. (5) CN should be accounted for in any analysis of atomic lines in this region. Publication: The Astrophysical Journal Pub Date: November 1972 DOI: 10.1086/151760 Bibcode: 1972ApJ...177..841M full text sources ADS | data products SIMBAD (3)

Infrared CN Bands in M Supergiants and Carbon Stars

view Abstract Citations (53) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared CN Bands in M Supergiants and Carbon Stars Wing, Robert F. ; Spinrad, Hyron Abstract Bands of the red system of CN in the region 1.1-2.5 ,s have been identified in published spectra of NI supergiants and carbon stars; their strengths are consistent wiU our observations of red CN bands in the 1- region. The CN features longward of 1.1 in I supergiants had previously been attributed to H2O; the revised identifications indicate that these stars have oxygen/carbon ratios very close to unity. In carbon stars the CN bands produce broad and deep depressions which cause an apparent weakening of the rotation-vibration bands of Co; the observed differences in CO strength among carbon stars are caused primarily by differences in the CN abundance. We note that the red system of CN is probably the most important of all bound-bound sources of opacity in K giants, K and I supergiants, and carbon stars. Publication: The Astrophysical Journal Pub Date: March 1970 DOI: 10.1086/150375 Bibcode: 1970ApJ...159..973W full text sources ADS | data products SIMBAD (16)