Mass transfer in the symbiotic binary AG Pegasi.

Line profiles, equivalent widths, and radial velocities have been derived from high-dispersion spectra of the symbiotic star AG Peg. The model suggested from recent spectra is a hot, approximately 1 M0 subluminous star orbiting a 3 M0 giant. The hot object rotates rapidly and ejects material which streams toward the cool primary. A bright region near the substellar point on the M star is responsible for a 0.3 mag light variation, and is heated either by radiation from the hot star or by collisions from the impinging stream. It is found that the size of the emission nebula surrounding the hot object has decreased, while its excitation has increased, since Merrill's observations several decades ago. At the same time, the stream density appears to have increased. An expanding, low-density envelope surrounds the system. The exact orbital period remains uncertain because of complications in the interpretation of the velocities from several regions, but a value of 820d is adopted. The system is thought to be in a late stage of its evolution, but it is not clear what forces (perhaps magnetic?) drive the stream, since the stars are well separated. Subject headings: binaries - combination spectra - mass loss - stars, individual