DIFFERENTIAL PHOTOMETRY AND ABSOLUTE SPECTROPHOTOMETRY OF CH CYGNI.

Abstract

ABSTRACT The symbiotic variable CH Cyg has been observed with four-color, H-beta, and other narrow band photometry during a brightening phase between June and November 1981, plus one night each in 1982 and 1983. Both differential photometry and the absolute energy distributions derived from the filters are presented, and an absolutely calibrated Reticon spectrogram taken near maximum brightness in 1982 provides continuum and integrated line fluxes. The data are consistent, with a binary-star hypothesis in which the variation is caused largely by the activity of the hot component. As the star brightened by 0.76 mag at y between June 11 and November 6, 1981, it became somewhat bluer, with a decrease in the (b-y) color index of 0.30 mag. Color changes shortward of b were much smaller. The small flickering variations discovered earlier are readily apparent. The H-beta emission-line fluxes extracted from the wide and narrow-band H-beta filters, as well as from the Reticon spectrum, correlate linearly with the fluxes at u, clearly demonstrating that the emitting mechanism for the line is controlled by the hot component alone. The data from 1982 are closely consistent with those from 1981.