BATC 13 Band Photometry of the Open Cluster NGC 7789

We present 13-band CCD intermediate-band spectrophotometry of a fieldcentered on the open cluster NGC 7789 from 400 to nearly 1000 nm, taken withBeijing-Arizona-Taiwan-Connecticut (BATC) Multi-Color Survey photometricsystem. By comparing observed spectral energy distributions of NGC 7789 starswith theoretical ones, the fundamental parameters of this cluster are derived:an age of $1.4\pm0.1$ Gyr, a distance modulus $(m-M)_{0}=11.27\pm0.04$, areddening $E(B-V)=0.28\pm0.02$, and a metallicity with the solar composition$Z=0.019$. When the surface density profile for member stars with limitingmagnitudes of 19.0 in the BATC $e$ band ($\lambda_{\textrm{eff}}=4925$ \AA) isfitted by King model, the core radius $R_{c}=7.52\arcmin$ and the tidal radius$R_{t}=28.84\arcmin$ are derived for NGC 7789. The observed mass function (MF)for main sequence stars of NGC 7789 with masses from 0.95 to 1.85 $M_{\odot}$is fitted with a power-law function $\phi(m)\propto m^{\alpha}$ and the slope$\alpha=-0.96$ is derived. Strong mass segregation in NGC 7789 is reflected inthe significant variation of the concentration parameters $C_{0}=\log(R_{t}/R_{c})$ for member stars of NGC 7789 within different mass ranges:$C_{0}=1.02$ for most of massive stars; $C_{0}=0.37$ for the lowest-mass MSstars. Strong mass segregation in NGC 7789 is also indicated in the significantvariation of the slopes $\alpha$ in different spatial regions of the cluster:the MF for stars within the core region has $\alpha=-0.71$, much flatter thanthat for stars in external regions of the cluster ($\alpha=-1.20$).Comment: 24 pages. AJ accepte