Delta Scuti Stars in Stellar Systems: the interest of HD 220392 and HD 220391

Abstract

The very wide double star CCDM 23239-5349 is an interesting study case of a pulsating star within a common origin pair or wide binary. Both stars are located in the Delta Scuti instability strip. Based on data obtained at La Silla (Chile), at the Swiss 0.7m and the ESO 0.5m telescopes, we found two periodicities of about 4.7 and 5.5 cycles per day (cpd) with amplitudes of 0.014 and 0.011 mag, respectively, for HD 220392, the brightest member of the system. The most dominant periodicity was also detected in the Hipparcos Epoch Photometry data. A similar period search on the (smaller) dataset obtained for the 1 mag fainter B-component, HD 220391, however shows no periodic behaviour with an amplitude significantly above the noise level of the data (about 0.006 mag).