Symbiotic stars on Asiago archive plates. I

Abstract

The rich plate archive of the Asiago observatory has been searched for plates containing the symbiotic stars AS 323, Ap 3-1, CM Aql, V1413 Aql (=AS 338), V443 Her, V627 Cas (=AS 501) and V919 Sgr. The program objects have been found on 602 plates, where their brightness has been estimated against the UBVRI photometric sequences calibrated by Henden and Munari (2000, A&AS 143, 343). AS 323 is probably eclipsing, with a preliminary P=197.6 day period. If confirmed, it would be the shortest orbital period known among symbiotic stars. CM Aql does not seem to undergo a series of outbursts, its lightcurve being instead modulated by a large amplitude sinusoidal variation with a P~1058 day period. V627 Cas presents a secular trend in agreement with the possible post-AGB nature of its cool component.