We report on a UV-oriented imaging survey in the fields of the old, metal-rich open clusters, NGC 6791, NGC 6819 and NGC 7142. These three clusters represent both very near and ideal stellar aggregates to match the distinctive properties of the evolved stellar populations, as in elliptical galaxies and bulges of spirals. The CMD of the three clusters is analyzed in detail, with special emphasis to the hot stellar component. We report, in this regard, one new extreme horizontal-branch star candidate in NGC 6791. For NGC 6819 and 7142, the stellar luminosity function points to a looser radial distribution of faint lower Main Sequence stars, either as a consequence of cluster dynamical interaction with the Galaxy or as an effect of an increasing fraction of binary stars toward the cluster core, as actually observed in NGC 6791 too.
Here we have obtained the {\it BVRI CCD} photometry down to a limiting magnitude of $V \sim$ 20 for the southern poorly studied open cluster NGC 6631. It is observed from the {\it 1.88 m} Telescope of Kottamia Observatory in Egypt. About 3300 stars have been observed in an area of $\sim 10^{\prime} \times 10^{\prime}$ around the cluster center. The main photometric parameters have been estimated and compared with the results that determined for the cluster using {\it JHKs 2MASS} photometric database. The cluster's diameter is estimated to be 10 arcmin; the reddening E(B-V)= 0.68 $\pm$ 0.10 mag…
We have conducted VI CCD photometry of the two open clusters NGC 1245 and NGC 2506 using the CFH12K CCD camera. Our photometry covers a sky area of 84'X82' and 42'X81' for the two clusters, respectively, and reaches down to V = 23. We derived the physical parameters using detailed theoretical isochrone fittings using 2 minimization. The derived cluster parameters are E(B-V) = 0.24+/-0.05 and 0.03+/-0.04, (V-M_V)_0 = 12.25+/-0.12 and 12.47+/-0.08, age(Gyr) = 1.08+/-0.09 and 2.31+/-0.16, and [Fe/H]= -0.08+/-0.06 and -0.24+/-0.06, respectively for NGC 1245 and NGC 2506, We present the luminosity …
The fundamental parameters of reddening, metallicity, age, and distance are presented for the poorly studied open clusters Be~89, Ru~135, and Be~10, derived from their CCD UBVRI photometry. By fitting the appropriate isochrones to the observed sequences of the clusters in five different color--magnitude diagrams, the weighted averages of distance moduli and heliocentric distances ($(V_0$--$M_{V}), d$(kpc)) are $(11\fm90\pm 0\fm06, 2.4\pm 0.06$) for Be~89, $(9\fm58\pm 0\fm07, 0.81\pm 0.03$) for Ru~135, and $(11\fm16\pm 0\fm06, 1.7 \pm 0.05$) for Be~10, and the weighted averages of the ages $(\l…
We present for the first time CCD SDSS gr photometry, obtained at the Gemini South telescope with the GMOS attached, of stars in the field of the poorly studied star clusters NGC1768, HS85, SL676, NGC2107, NGC2190, and SL866, which are distributed in the main body of the Large Magellanic Cloud. We applied a subtraction procedure to statistically clean the cluster CMDs from field star contamination. In order to disentangle cluster features from those belonging to their surrounding fields, we applied a subtraction procedure which makes use of variable cells to reproduce the field star Color-Magn…
A new CCD photometry survey of the open cluster NGC7788 in U, B, V, R and I colors to magnitude V=20 is present. Extensive comparison of our photometry with other published dataset shows excellent agreement, indicating that CCD photometry is capable of producing a uniform set of measurements consistent with the photometric system defined primarily by the Landolt standard sequence. For this study we used the 113 stars considered to be cluster members by Becker on 1965.
The poorly studied Berkeley 8 (Be8) open cluster is analysed from CCD UBVRI photometric data taken with the 0.90 m telescope at the Sierra Nevada Observatory. The Z = +0.008 PARSEC isochrone gave us a reddening of E(B-V) = 0.69 +- 0.03, a distance of 3410 +- 300 pc and an age of 2.8 +- 0.2 Gyr. Its median Gaia DR2 distance, d = 3676 +- 810 pc is in good agreement with our photometric distances, 3410 - 3620 pc within the uncertainties. The kinematic parameters of five likely members of Be 8 with the circular orbits, ecc = [0.23, 0.30] reflect the properties of the Galactic thin disc, which is a…
In this paper we present photometric CCD observations of the globular cluster NGC 6093 (M80) in filters B, V , R and I. We produce the colour-magnitude diagrams for this object and obtain values for its metallicity [Fe/H], reddening E(V-B), E(V-I) and distance modulus (m - M)_0.
The CCD UBV(RI)KC photometry of the poorly studied open clusters Juchert 9 (Juc 9) and Berkeley 97 (Be 97), which are observed with the 0.84 m telescope at the San Pedro Mártir National Observatory, México has been analysed. For the likely cluster members, we determined the reddenings, E(B-V)=0.82 +- 0.04 (Juc 9) and E(B-V)=0.87 +- 0.05 (Be 97), from the early type stars. Our distance moduli/distances for only (B - V) colour are (Vo-Mv , d(kpc)) = (13.40 +- 0.10, 4.8 +- 0.2 kpc) (Juc 9) and (12.40 +- 0.12, 3.0 +- 0.2 kpc) (Be 97), respectively. The Gaia DR2 distances are d = 4.5 +- 1.2 kpc (Ju…
Fundamental astrophysical parameters have been derived for Be 55 open cluster based on UBVI CCD photometric data, observed with the AZT-22 1.5m telescope at Maidanak Astronomical Observatory in Uzbekistan. The mean reddening is obtained as E(B-V)=1.77+-0.10 mag from early type members. The zero age main sequence fitting in the Q(VA)- Q0 diagrams indicates the distance modulus, (V0 - MV)=12.4+-0.20 mag (d=3.02+-0.28 kpc). This photometric distance is consistent with the distances of Gaia EDR3 (d=3.09+-0.16 kpc) and period-luminosity relation (d=2.78+-0.32 kpc) of its Cepheid S5 within the uncer…
All available CCD observation of RV UMa have been analyzed to obtain an accurate mathematical description of the ligh variation. We discuss in this paper a new study of variable star RV UMa, a short period RRab star, in orther to determine through the light curve and the physical parameters, the presence of "Blazhko effect". The Star were observed for a total of 839 sessions shooting, and exhibits light curve modulation with the shortest modulation Period=0.468002 ever observed. The result detect small but definite modification in temperature and mean radius of the star itself. All results are…
We present and discuss new CCD-based photometric material in the UBVI pass-bands for nine Galactic star clusters located inside the solar ring, for which no CCD data are currently available. They are: IC 2714, NGC 4052, ESO131SC09, NGC 5284, NGC 5316, NGC 5715, VdB-Hagen ~164, NGC 6268, and Czernik 38. We first perform star counts by combining our optical photometry wi th 2MASS, and derive cluster sizes and radial density profiles. The fundamental parameters - age, reddening and distance- are then inferred from the analysis of the star distribution in color-color and color-magnitude diagrams o…
Fundamental astrophysical parameters have been derived for 20 open clusters (O\!Cs) using CCD~$U\!BV\!(RI)_C$ photometric data observed with the 84~cm telescope at the San Pedro Mártir National Astronomical Observatory, México. The interstellar reddenings, metallicities, distances, and ages have been compared to the literature values. Significant differences are usually due to the usage of diverse empirical calibrations and differing assumptions, such as concerning cluster metallicity, as well as distinct isochrones which correspond to differing element-abundance ratios, internal stellar physi…
We present the results of CCD UBVRI observations of the open cluster NGC 6811 obtained on 18th July 2012 with the 1m telescope at the TÜBİTAK National Observatory (TUG). Using these photometric results, we determine the structural and astrophysical parameters of the cluster. The mean photometric uncertainties are better than 0.02 mag in the V magnitude and B-V, V-R, and V-I colour indices to about 0.03 mag for U-B among stars brighter than magnitude V=18. Cluster member stars were separated from the field stars using the Galaxia model of Sharma et al. (2011) together with other techniques. The…
We present reddening, photometric metallicity, age and distance estimates for the Frolov 1 and NGC 7510 open clusters based on CCD UBV photometric and Gaia data. Photometric observations were collected using the 1-m telescope of the TÜBİTAK National Observatory. Gaia DR2 proper motion data in the direction of two groupings were used to identify cluster membership. We determined mean proper motion values ($ μ_α\cosδ, μ_δ$) = ($-3.02\pm 0.10$, $-1.75 \pm 0.08$) and ($-3.66 \pm 0.07$, $-2.17 \pm 0.06$) mas yr$^{-1}$ for Frolov 1 and NGC 7510, respectively. We used two-colour diagrams to obtain $E…
We present a comprehensive photometric study of the old open cluster, NGC 6819 using 1x1 degree field VI MOSAIC CCD imaging taken with the WIYN 0.9m telescope. The resultant color-magnitude diagram (CMD) shows a well developed main sequence (MS) extending from V~14.5 mag down to our photometric limit of V~21 mag. Fitting theoretical isochrones with adopted values of the reddening and metallicity (E(B-V)=0.14, [Fe/H]=+0.09 dex) to the observed CMD yields a distance modulus of (m-M)_{0}=11.93+/-0.10 and an age of ~2.6 Gyr for NGC 6819. Our wide-field imaging reveals that NGC 6819 is larger in ar…
We present the results of a deep, wide-field CCD survey for the open cluster NGC~3532. Our new $BV(RI)_{c}$ photometry effectively covers a one square degree area and reaches an unprecedented depth of $V\sim21$ to reveal that NGC~3532 is a rich open cluster that harbors a large number of faint, low-mass stars. We employ a number of methods to reduce the impact of field star contamination in the cluster color-magnitude diagrams, including supplementing our photometry with $JHK_{s}$ data from the 2MASS catalog. These efforts allow us to define a robust sample of candidate main sequence stars sui…
We present the results of the $UBVI_C$ variability survey in the young open cluster NGC 6611 based on observations obtained during 34 nights spanning one year. In total, we found 95 variable stars. Most of these stars are classified as periodic and irregular pre-main sequence (PMS) stars. The analysis of the $JHK_S$ 2MASS photometry and four-colour IRAC photometry revealed 165 Class II young stellar sources, 20 of which are irregular variables and one is an eclipsing binary. These classifications, complemented by $JHK$ UKIDSS photometry and $riHα$ VPHAS photometry, were used to identify 24 can…
We present high-quality CCD photometry in the Washington system C and T1 passbands down to T1 ~ 19.5 mag in the fields of 10 Galactic open clusters (OCs) or candidates projected close to the Galactic plane, namely: ESO 313-SC03, BH 54, Ruprecht 87, ESO 129-SC32, BH 217, Collinder 347, Basel 5, Ruprecht 144, Archinal 1 and Berkeley 82. Four of these objects are located toward the Galactic centre direction within a solid angle of 21 deg. No photoelectric or CCD photometry in the optical domain has been so far reported for five of these objects. Cluster radii are estimated from radial density pro…
We report the results of CCD $V$, $r$ and $I$ time-series photometry of the globular cluster NGC 5053. New times of maximum light are given for the eight known RR Lyrae stars in the field of our images and their periods are revised. Their $V$ light curves were Fourier decomposed to estimate their physical parameters. A discussion on the accuracy of the Fourier-based iron abundances, temperatures, masses and radii is given. New periods are found for the 5 known SX Phe stars and a critical discussion of their secular period changes is offered. The mean iron abundance for the RR Lyrae stars is fo…
We present the results of CCD UBV observations of the open cluster NGC 6819. We calculated the stellar density profile in the cluster's field to determine the structural parameters of NGC 6819. Using the existing astrometric data, we calculated the probabilities of the stars being physical members of the cluster, and used these objects in the determination of the astrophysical parameters of NGC 6819. We inferred the reddening and metallicity of the cluster as $E(B-V)=0.130\pm0.035$ mag and $[Fe/H]=+0.051\pm 0.020$ dex, respectively, using the U-B vs B-V two-colour diagram and UV excesses of th…
We have surveyed a complete extent of Leo A - an apparently isolated gas-rich low-mass dwarf irregular galaxy in the Local Group. The $B$, $V$, and $I$ passband CCD images (typical seeing $\sim$0.8") were obtained with Subaru Telescope equipped with Suprime-Cam mosaic camera. The wide-field ($20' \times 24'$) photometry catalog of 38,856 objects ($V \sim 16-26$ mag) is presented. This survey is also intended to serve as "a finding chart" for future imaging and spectroscopic observation programs of Leo A.
We present the results of CCD $UBV$ photometric and spectroscopic observations of the open cluster NGC 225. In order to determine the structural parameters of NGC 225, we calculated the stellar density profile in the cluster's field. We estimated the probabilities of the stars being physical members of the cluster using the existing astrometric data. The most likely members of the cluster were used in the determination of the astrophysical parameters of the cluster. We calculated the mean radial velocity of the cluster as $V_{r}=-8.3\pm 5.0$ km s$^{-1}$ from the optical spectra of eight stars …
Precision uvbyCaHbeta photometry of the nearby old open cluster, NGC 752, is presented. The mosaic of CCD fields covers an area ~42' on a side with internal precision at the 0.005 to 0.010 mag level for the majority of stars down to V~15. The CCD photometry is tied to the standard system using an extensive set of published photoelectric observations adopted as secondary standards within the cluster. Multicolor indices are used to eliminate as nonmembers a large fraction of the low probability proper-motion members near the faint end of the main sequence, while identifying 24 potential dwarf me…
We present $UBVRI$ photometry of 8702 stars in a $0.5 ^\circ\times0.5 ^\circ$ field in the direction of NGC 7142, taken with the Half Degree Imager (HDI) at the WIYN 0.9-meter telescope, to improve knowledge of this cluster's basic parameters. Our photometry spans the ranges 10.6 - 20.4 mag in $U$, 10.6 - 22.0 mag in $B$, 10.0 - 21.8 mag in $V$, 9.2 - 20.7 mag in $R$, and 8.5 - 19.9 mag in $I$. Using color-color diagrams that employ all four color combinations that include $U$, versus $B-V$, we derive a reddening-metallicity relation for the cluster, with preferred values $E(B-V$) = 0.338 $\pm…
Precision CCD uvbyCaHbeta photometry is presented of the old cluster, M67, covering one square degree with typical internal precision at the 0.005-0.020 mag level to V~17. The photometry is calibrated using standards over a wide range in luminosity and temperature from NGC 752 and zeroed to the standard system via published photoelectric observations. Relative to NGC 752, differential offsets in reddening and metallicity are derived using astrometric members, supplemented by radial-velocity information. From single-star members, offsets in the sense (M67 - NGC 752) are Delta E(b-y) = -0.005 +/…
Young star clusters consisting of massive stars are the ideal sites to study the star formation processes and influence of massive stars on the subsequent star formation. NGC 1893 is a young star cluster associated with the HII region Sh2-236. It contains about five `O'-type stars and several early `B'-type stars. It is located at a distance of $\sim$3.25 kpc and has a reddening, E(B-V)$\sim$0.4 mag. To characterize the young low-mass stellar population in the central portion of the cluster, we carried out deep VI band observations of the region using the 4K$\times$4K CCD IMAGER mounted on the…
CCD () photometry of the open cluster NGC 6793 and its dynamical evolution
Institute of Graduate Studies In Sciences, İstanbul University（伊斯坦布尔大学研究生院）；Department of Astronomy and Space Sciences, Science Faculty, İstanbul University（伊斯坦布尔大学理学院天文与空间科学系）；Observatorio Astronómico Nacional, Universidad Nacional Autónoma de México（墨西哥国立自治大学国家天文台）；Universidade Federal do Rio Grande do Sul（南里奥格兰德联邦大学）；Department of Science History, Faculty of Arts and Sciences, Medeniyet University（梅德尼耶特大学文理学院科学史系）；Department of Astronomy and Space Sciences, Faculty of Arts and Sciences, Erciyes University（埃尔吉耶斯大学文理学院天文与空间科学系）；Huawei Türkiye Research and Development Center（华为土耳其研发中心）
本文通过新的 CCD UBV(RI)KC 光度测量确定了开放星团 NGC 6793 的新天体物理参数，研究了其年龄、距离模数以及动态演化过程，揭示了其内部结构和外部扰动的相互作用。
