A comprehensive study of the delta Scuti star, 57 Tauri (= HR 1351) in theHyades cluster

A comprehensive frequency analysis of 57 Tau, supposed only a static pulsat ional arrangement, is presented based on 54 nights of photometric data coll ected between 1981 and 1995 (altogether 232 hours). The presence of individ ual frequencies is confirmed by intercomparing four subsets of this data se t, however, the uncertainties in data coming from the sparse nights and low signal weaken the conclusion on some results. The entire data base is then used to resolve closely spaced peaks. Twelve frequencies are indentified u sing this process. Further multisite observations are recommended to confir m the present frequency solution. Two periods, with a high probability of b eing real, are found in the low frequency domain. They are suggested to ari se from binarity or g modes, as in gamma Dor stars. Single unusual cycles, possessing large amplitude, or displaying asymmetry, have been localized. A coherent frequency at 29.83 c/d with variable amplitude was found. The non standard behaviour of the light variation indicates that nonlinear and/or n onstationary processes could be very important in the investigation of delt a Scuti observations.