We present a photometric study of the globular clusters (GCs) in the giant elliptical galaxy M60 in the Virgo Cluster, based on deep, relatively wide field Washington CT_1_ CCD images. The CMD reveals a significant population of GCs in M60 and a large number of young luminous clusters in NGC 4647, a small companion spiral northwest of M60. The color distribution of the GCs in M60 is clearly bimodal, with a blue peak at (C-T_1_)=1.37 and a red peak at (C-T_1_)=1.87. We derive two new transformation relations between the (C-T_1_)_0_ color and [Fe/H] using the data for the GCs in our Galaxy and M49. Using these relations, we derive the metallicity distribution of the GCs in M60, which is also bimodal: a dominant metal-poor component with center at [Fe/H]=-1.2, and a weaker metal-rich component with center at [Fe/H]=-0.2. We estimate the total number of the GCs in M60 to be 3600+/-500 and the specific frequency to be S_N_=3.8+/-0.4.
Two sets of observations of the metal-rich globular cluster M 71 are presented. The first uses deep CCD exposures to derive a fiducial in V, B-V and compares this with a cluster of similar metallicity, 47 Tuc. Comparison with oxygen enhanced theoretical isochrones leads to age estimates for M 71 of from ~14+/-2Gyr to ~16+/-2Gyr. Within the limits imposed by the quality of the data, no significant age difference between the two clusters is found. The second set of 73 frames is used to search an overlapping 67"x104" area of the cluster for variable stars. Light curves and phase diagrams (where appropriate) are presented for all four of the variables discovered. One variable blue straggler (or SX Phe star) has been identified with a period of 0.050d. Values for its mass depend, of course, on the assumed pulsation mode-(0.90+/-0.47)M_{sun}_ for the first overtone mode, and (1.57+/-0.83)M_{sun}_ for the fundamental mode. One of the variables, with a 0.0582d period, but with a magnitude 1.75mag below the main sequence turnoff may be a field star. Two candidate eclipsing binary systems were also found. The most likely orbital period of one is 0.372d. This value, and the shape of the light curve, suggest that it could be a W UMa type variable. No period was obtainable for the other candidate binary due to a lack of phase coverage. Further data is needed to confirm and strengthen these claims, and to check for cluster membership.
We present CCD photometric observations of 23 main-belt asteroids, of which 8 have never been observed before thus the data of these objects are the first in the literature. The majority showed well detectable light variations, exceeding 0.1m. We have determined synodic periods for 756 Lilliana (9.36),1270 Datura (3.4), 1400 Tirela (13.36), 1503 Kuopio (9.98), 3682 Welther (3.59), 7505 Furushu (4.14) and 11436 1969 QR (2.6), while uncertain period estimates were possible for 469 Argentina (12.3), 546 Herodias (10.4) and 1026 Ingrid (5.3). The shape of the lightcurves of 3682 Welther changed on a short time-scale and showed dimmings that might be attributed to eclipses in a binary system. For the remaining objects, only lower limits of the periods and amplitudes were concluded.
CCD photometry of the galactic open clusters NGC 2658, NGC 2849, and NGC 3247 is presented. For the first two clusters, BV(RI)_c data are given, and for NGC 3247 the data are BV(I)_c. The observations were carried out from the Complejo Astronomico El Leoncito (Argentina), and from Las Campanas (Chile). Each cluster was observed on two different nights; when possible, measurements for a given star were averaged. NGC 2658 observations were carried out from CASLEO on the nights of 8-9 January 1997 and 18-19 April 2001, in the BVRI filters. NGC 2849 data in the BVRI filters were obtained at Las Campanas on the night 10-11 April 1996, and at CASLEO on 19-20 April 2001. NGC 3247 was observed at CASLEO on the nights 16-17 January 1996 (BV) and 1-2 April 1998 (BVI). The given star coordinates are relative to the corresponding cluster center.
CCD B,V observations on the NGC 7142 (1950 position 21h44.7 +65d34') field reveal the presence of a single short-period variable star. The color-magnitude diagram of the field shows evidence for small-scale variable absorption across the face of the cluster. The age of NGC 7142 appears to be confirmed as intermediate between that of M67 and NGC 188, and a new distance-modulus is found to be (m-M)0 = 11.4 +/- 0.9
We present BV and u'g'r'i' CCD photometry of the central region of NGC 2482. We also present BVu'g' CCD photometry of five clusters that have been poorly studied in the past: Ruprecht 42, Ruprecht 51, Ruprecht 153, Ruprecht 154, and AH03 J0748-26.9, which to our knowledge has not been studied before. Using a global optimization technique that eliminates much of the subjectivity previously inherent in main-sequence fitting studies, we obtain values of the distances, ages, and metallicities of the clusters, with robust estimates of the uncertainties of these fundamental parameters. Four of our clusters are less than ~1.3kpc beyond the Sun's distance from the Galactic center and have essentially solar metallicity. The metallicities of those clusters more distant from the Galactic center are consistent with a 0.3dex step to lower [Fe/H] found in other studies.
In this paper we present results of CCD UBV photometry of stars in two young LMC clusters: NGC 2004 and 2100. A comparison of recent CCD investigations of these clusters shows large zero-point discrepancies.
B and V band CCD photometry is used to study 33 cluster and nine field RR Lyrae variables near the LMC cluster, NGC 2257. It is found that the mean magnitudes for the two groups differ by 0.17 mag. The cluster and field variables both have an Fe/H abundance ratio of -1.8+/-0.1. The results are compared used to compare NGC 2257 with galactic globular clusters, showing that NGC 2257 is indistinguishable from its local counterparts.
We present a CCD photometric survey of the central one-half degree of the old open cluster, M67, in U, B, V, and I colors to magnitude V=20. Extensive comparison of our photometry with other published datasets 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. The color-magnitude diagram of the cluster shows a well-defined main sequence extending at least to the limit of the photometry at M(V)=10.55 and a substantial binary sequence. At least 38 percent of cluster stars are binaries. The observations were performed on 3 nights on 15-18 February 1990 with the 1.09m telescope at Kitt Peak National Observatory with a Tektronix 512^2^ CCD camera; a standard KPNO UBVRI filter set was used, with BVR filters being the Harris et, and I the "nearly Mould" filter.
