A CCD search for variable stars of spectral type B in the Northern Hemisphere open clusters .2. NGC 7235

We report the discovery of nine variable stars in a 4' x 6' field covering NGC 7235. The variable stars include a beta Cep star, a Be short-period variable of the lambda Eri type, a Mira, a W UMa eclipsing binary, a candidate alpha Cyg variable, and a probable eclipsing binary. The remaining three variable stars could not be classified because of insufficient data. The beta Cep star, the lambda Eri variable, the candidate alpha Cyg variable, and the probable eclipsing binary are members of the cluster. We found no SPB stars in NGC 7235. For a number of stars in our field we also provide the I magnitudes and the R-I, V-I, and B-V color indices on the BV(RI)(c) system of Johnson, Kron and Cousins. We find large systematic effects for the faint photographic ii magnitudes. We define an alpha index which is a measure of the equivalent width of the H alpha line. We give the alpha index for 64 brightest stars in our field. Our alpha index revealed the Be nature of the above-mentioned lambda Eri variable.