Disklike Structure in the Semiregular Pulsating Star X Her

Abstract

The author presents the results of Berkeley-Illinois-Maryland (BIMA) array interferometric observations in the CO $J=1$–0 line toward X Her and EP Aqr, semiregular pulsating stars with a composite CO line profile, and also reports finding a disklike structure in X Her. In the CO spectrum both of X Her and EP Aqr, a composite profile including narrow and broad components is seen as reported by the previous single-dish observations. The spatial structure of the broad component region of X Her shows a bipolar shape, and that of the narrow component shows an elliptical/spherical shape. The blue- and red-shifted parts of the X Her narrow component show a systematic difference in the velocity integrated intensity map. The spatio-kinematic properties of the X Her narrow component are reminiscent of a Keplerian rotating disk with a central mass of 0.9 M$_{\odot}$. The spatial distributions of both the narrow and the broad components of EP Aqr appear to be roughly round with the same peak positions; no significant velocity gradient is seen. The spatio-kinematic properties of EP Aqr are reminiscent of a multiple-shell structure model rather than of a bipolar flow and disk model.