2007/01/10 by Zhenyu Wu, Zhen-Yu Wu, Xu Zhou +6 · 2 citations
Physics and Astronomy · #Astro and Planetary Science #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Distance modulus #Globular cluster #Mass segregation #Metallicity #Open cluster #Photometry (optics) #Physics #Solar mass #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/512189
published as Astron.J.133:2061-2071,2007 · 24 pages. AJ accepted
arxiv created 2007/01/10 · openalex publication_date 2007/03/26 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 the 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 ± 0.1 Gyr, a distance modulus ( m - M ) 0 = 11.27 ± 0.04, a reddening E ( B - V ) = 0.28 ± 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 (λ eff = 4925 Å) is fitted by a King model, a core radius R c = 7.52' and a tidal radius R t = 28.84' are derived for NGC 7789. The observed mass function (MF) for main-sequence (MS) stars of NGC 7789 with masses from 0.95 to 1.85 M ⊙ is fitted with a power-law function ϕ( m ) ∝ m α , and a slope α = -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 the most massive stars and 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 α in different spatial regions of the cluster: the MF for stars within the core region has α = -0.71, much flatter than that for stars in external regions of the cluster (α = -1.20).