• Journal of The Korean Astronomical Society
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• v.38 no.4
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• pp.429-435
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• 2005

We present BV CCD photometry for the open clusters Czernik 24 and Czernik 27. These clusters have never been studied before, and we provide, for the first time, the cluster parameters; reddening, distance, metallicity and age. Czernik 24 is an old open cluster with age $1.8{\pm}0.2Gyr$, metallicity $[Fe/H]=-0.41{\pm}0.15dex$, distance modulus $(m-M)_0=13.1{\pm}0.3mag$ ($d=4.1{\pm}0.5kpc$), and reddening $E(B-V)=0.54{\pm}0.12mag$. The parameters for Czernik 27 are estimated to be $age=0.63{\pm}0.07Gyr$, $[Fe/H]=-0.02{\pm}0.10dex$, $(m-M)_0=13.8{\pm}0.2mag$ ($d=5.8{\pm}0.5kpc$), and $E(B-V)=0.15{\pm}0.05mag$. The metallicity and distance values for Czernik 24 are consistent with the relation between the metallicity and the Galactocentric distance of other old open clusters. We find the metallicity gradient of 51 old open clusters including Czernik 24 to be ${\Delta}[Fe/H]/{\Delta}R_{gc}=-0.064 {\pm}0.009dex\;kpc^{-1}$.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.363-376
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• 2005

To study the effects of giant population on dynamical substructures of the central region of NGC 7006, we examine the radial variations of ellipticity and position angle on By stellar photometry using ellipse fitting technique. Total variations of ellipticity and position angle lie in the range $0.02\~0.06\;and\;-10^{\circ}+90^{\circ}$, respectively, from the center out to three times the half light radius. Our ellipse fitting results, after removing giant populations, show that the apparent central dynamical substructures of NGC 7006 are mainly affected by red giant, horizontal branch stars. On the contrary, the contribution of light from subgiant stars to the inner dynamical substructure seems to be insignificant.

• Journal of The Korean Astronomical Society
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• v.50 no.3
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• pp.79-92
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• 2017

We present a BV I optical photometric study of the old open cluster Ruprecht 6 using the data obtained with the SMARTS 1.0 m telescope at the CTIO, Chile. Its color-magnitude diagrams show the clear existence of the main-sequence stars, whose turn-off point is located around $V{\approx}18.45mag$ and $B-V{\approx}0.85mag$. Three red clump (RC) stars are identified at V = 16.00 mag, I = 14.41 mag and B - V = 1.35 mag. From the mean $K_s-band$ magnitude of RC stars ($K_s=12.39{\pm}0.21mag$) in Ruprecht 6 from 2MASS photometry and the known absolute magnitudes of the RC stars ($M_{K_S}=-1.595{\pm}0.025mag$), we obtain the distance modulus to Ruprecht 6 of $(m-M)_0=13.84{\pm}0.21mag$ ($d=5.86{\pm}0.60kpc$). From the ($J-K_s$) and (B - V ) colors of the RC stars, comparison of the (B - V ) and (V - I) colors of the bright stars in Ruprecht 6 with those of the intrinsic colors of dwarf and giant stars, and the PARSEC isochrone fittings, we derive the reddening values of E(B - V ) = 0.42 mag and E(V - I) = 0.60 mag. Using the PARSEC isochrone fittings onto the color-magnitude diagrams, we estimate the age and metallicity to be: $log(t)=9.50{\pm}0.10(t=3.16{\pm}0.82Gyr)$ and $[Fe/H]=-0.42{\pm}0.04dex$. We present the Galactocentric radial metallicity gradient analysis for old (age > 1 Gyr) open clusters of the Dias et al. catalog, which likely follow a single relation of $[Fe/H]=(-0.034{\pm}0.007)R_{GC}+(0.190{\pm}0.080)$ (rms = 0.201) for the whole radial range or a dual relation of $[Fe/H]=(-0.077{\pm}0.017)R_{GC}+(0.609{\pm}0.161)$ (rms = 0.152) and constant ([Fe/H] ~ -0.3 dex) value, inside and outside of RGC ~ 12 kpc, respectively. The metallicity and Galactocentric radius ($13.28{\pm}0.54kpc$) of Ruprecht 6 obtained in this study seem to be consistent with both of the relations.