SOURCE FUNCTIONS OF SOME STRONG LINES IN LATE-TYPE STELLAR ATMOSPHERES

The classification of the source functions of some strong spectral lines in the atmospheres of late-type stars is discussed. Using Arcturus as an example it is shown that the Hϵ emission seen in some late-type giants is the result of a photoelectrically controlled source function. In the cool dwarfs however the emission sometimes seen in the Balmer series and some strong neutral metal resonance lines results, like the Ca II H and K emission, from a chromospheric temperature rise coupled with a collisionally controlled source function. © 1974 Royal Astronomical Society. Provided by the NASA Astrophysics Data System.