H and K Emission in Late-Type Stars: Dependence of Line Width on Luminosity and Related Topics.

Abstract

view Abstract Citations (423) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS H and K Emission in Late-Type Stars: Dependence of Line Width on Luminosity and Related Topics. Wilson, O. C. ; Vainu Bappu, M. K. Abstract The H and K emission lines of Ca II have been studied on 10-A/mm spectrograms of 185 stars of types G, K, and M. Nearly all stars of type G0 or later in the list of MK standards (Johnson and Morgan 1953) have been included. Emission-line widths have been measured, as well as displacements of the emission and absorption components. Tb e displacements are determined with respect to nearby low-excitation reversing- layer absorption lines. When the logarithms of the emission-line widths (corrected for instrumental width) are plotted against the Yerkes absolute spectroscopic magnitudes, the points define a straight line which extends over a 15-mag. range of Mv and which indicates that the line width varies as the one-sixth power of the luminosity. Stars with weak or strong lines and of all spectral types later than G0 seem to fit the linear relationship equally well. The widths therefore cannot be dependent upon line intensity or stellar surface temperature. Evidence from the solar spectrum, from ζ Aurigae, from Hyades stars, and from four visual binaries point to the conclusion that the relationship described here is not of a statistical nature. Therefore, it is probable that the Ca II emission-line widths can be used as luminosity indicators. Internal consistency considerations indicate that one good spectrogram should fix the absolute magnitude of any late-type star with suitable lines to within ±05 mag. It is found that,for displacements within ±6 km/sec, negative values are more frequent than positive for the emission components of H and K. On the other hand, between +4 and -4 km/sec, positive values are more common for the absorption components. The naive interpretation is that the emitting layer is rising and that the absorbing material is falling slowly inward. Statistics of the larger displacements common among the intrinsically luminous stars are discussed briefly. In particular, it is found that among the M-type giants and supergiants the negative displacements of the absorption components are not correlated with absolute magnitude. Publication: The Astrophysical Journal Pub Date: May 1957 DOI: 10.1086/146339 Bibcode: 1957ApJ...125..661W full text sources ADS | data products SIMBAD (184) Related Materials (1) Commentary: 1999ApJ...525C.776L