B-type variables in the young open cluster NGC457

摘要

We have performed long-term, two-color time-series CCD photometry of the young open cluster NGC457 to search for B-type variables. The light variations of about 400 stars located in a 165 × 165 field of the cluster were examined. It resulted in the detection of 13 periodic variables, including 8 B-type variables. With the two-color photometric data, we have constructed a color-magnitude diagram for the cluster. A brief isochrone fitting yields a reddening of E(B - V) = 0.46 ± 0.05 and a distance modulus of (m - M) _V = 13.30 ± 0.10 with an age of log(Age) = 7.30. With the above results, we identified three probable member stars in addition to six certain ones from the new variable sample. Through a preliminary photometric analysis with the obtained B- and V-band light curves, we have determined the amplitude and period of light variations for each of the variables. Based on this, the physical properties and classification of the detected variables are discussed. As a conclusion, we have identified one β Cep, five candidate SPB stars, and three δ Scuti-type pulsating stars plus three EA-type eclipsing binaries and one EW-type one in NGC457.