BATC 13-band Photometry of Open Cluster NGC 7789

Abstract

We present 13-band CCD intermediate-band spectrophotometry of a field centered on the open cluster NGC 7789 from 400 to nearly 1000 nm, taken with Beijing-Arizona-Taiwan-Connecticut (BATC) Multi-Color Survey photometric system. By comparing observed spectral energy distributions of NGC 7789 stars with theoretical ones, the fundamental parameters of this cluster are derived: an age of $1.4\pm 0.1$ Gyr, a distance modulus $(m-M{)}_0=11.27\pm 0.04$, a reddening $E(B-V)=0.28\pm 0.02$, and a metallicity with the solar composition $Z=0.019$. When the surface density profile for member stars with limiting magnitudes of 19.0 in the BATC $e$ band (${\lambda }_{\text{eff}}=4925$ Å) is fitted 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 $\varphi (m)\propto m^{\alpha }$ and the slope $\alpha =-0.96$ is derived. Strong mass segregation in NGC 7789 is reflected in the 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 MS stars. Strong mass segregation in NGC 7789 is also indicated in the significant variation 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 than that for stars in external regions of the cluster ($\alpha =-1.20$).

24 pages. AJ accepted

Cited by in corpus (1)

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