Abstract
ABSTRACT Radial-velocity curves of various features in 19 spectra of the 16-day cepheid X Cyg are presented and analyzed, with a focus on the anomalous behavior of H-alpha. Spectra were obtained sequentially over 3, 5, and 7 days and on three isolated days in 1977-1980, during rising light phases of the variable star (between phases 0.6 to 0.2). O98 plates were used with a 1200-line/mm grating in the 0.8-m camera on the 1.2-m telescope at Dominion Astrophysical Observatory, with a dispersion of 10 A/mm. The red-displaced H-alpha component appearing at about phase 0.8 and decreasing to about the center-of-mass velocity (8 km/sec), and the violet-displaced component appearing near the maximum are characterized, and mechanisms are proposed to explain them. While the latter is probably related to the Ca II emission, the former is attributed to velocity gradients in the outer envelope and L-alpha and collisional excitation of the 2s metastable state of H.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
