CCD BV Photometry Research Articles

BV photometry of a possible open star cluster pair NGC 7031/NGC 7086

AbstractWe present a CCD BV photometry of the possible binary open star cluster NGC 7031/NGC 7086. The aim is to confirm or disprove their common nature on the grounds of their age and distance. An age of 224 ± 25 Myr and a distance of 831 ± 72 pc was determined for NGC 7031, and 178 ± 25 Myr, 955 ± 84 pc for NGC 7086, respectively. Based on these differences in age and distance we conclude that the two clusters are most likely not formed together from one and the same giant molecular cloud and thus do not form a true binary cluster. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Intermediate-age open clusters: Collinder 110

We present CCD BV photometry of the intermediate age open cluster Collinder 110, a nearby, scarcely populated, and poorly studied system. There is no literature information on the metallicity, so we tested several possibilities, and found a slight evidence of sub-solar abundances. Using the synthetic Colour - Magnitude Diagrams technique we estimate the following parameters: age between 1.1 and 1.5 Gyr, reddening 0.38 <~ E(B-V) <~ 0.45, distance modulus (m-M)o between 11.45 and 11.7 if the cluster metallicity is sub-solar.

WIYN Open Cluster Study. VII. NGC 2451A and the [ITAL]HIPPARCOS[/ITAL][ITAL]Hipparcos[/ITAL] Distance Scale

We provide new evidence that NGC 2451A is undoubtedly a young open cluster, although sparsely populated. New cluster membership has been derived from relative proper motions of 5868 stars. In total, 136 stars down to V ~ 15 have membership probability Pμ ≥ 2%. New CCD BV photometry indicates that about 70 stars are indeed main-sequence stars of NGC 2451A. This is also supported by our measurements of radial velocities. A total of 34 very likely cluster members yield a mean heliocentric radial velocity for NGC 2451A equal to +22.9 km s-1. The high quality of our BV photometry, a confirmation of cluster membership from proper motions and radial velocities, and a recently obtained metallicity estimate for several cluster stars allow us to perform a precise isochrone fit. The Yale isochrones, updated by the latest available input physics, have been fitted to the cluster's color-magnitude diagram, yielding a distance modulus V0 - MV in the range 6.35 to 6.38, which is in excellent agreement with the distance modulus (m - M)0 = 6.38 derived from the Hipparcos data recently by van Leeuwen and Robichon et al. For NGC 2451A the isochrone fit yields an age of 60 ± 20 Myr; hence, the cluster appears to be somewhat younger than the Pleiades. We also present alternative evidence suggesting that the cluster could be slightly older than the Pleiades. The most important result of this study is an excellent match between the main-sequence fitting and Hipparcos distances to NGC 2451A. If we consider noticeable similarities between NGC 2451A and Pleiades, then the Hipparcos distance anomaly for Pleiades may not require an explanation of astrophysical nature.

CCD Photometry of the Globular Cluster NGC 5986 and Its Post–Asymptotic Giant Branch and RR Lyrae Stars

We have obtained new CCD BV photometry of the little-studied southern Galactic globular cluster NGC 5986, including light curves of five of its RR Lyrae variables. The cluster's red giant branch bump is detected for the first time, at V = 16.47 ± 0.03. We derive a reddening and true distance modulus of E(B-V) = 0.29 ± 0.02 and (m - M)0 = 15.15 ± 0.10, respectively. The cluster's color-magnitude diagram reveals a mostly blue horizontal branch, like that of M13 or M2, and quite unlike M3; yet all of these clusters have nearly identical metallicities ([Fe/H]CG97 = -1.35). We show that the RR Lyrae variables in NGC 5986 are about 0.2 mag brighter on average than those in M3, an important exception to the often-employed, universal MV(RR)-[Fe/H] relation. Finally, we note that NGC 5986 contains two luminous stars with spectral types A–F, which are likely to be post–asymptotic giant branch (PAGB) objects. The V-band luminosity function of such yellow PAGB stars is a promising standard candle. We suggest that the luminosity function is sharply peaked at MV(PAGB) = -3.28 ± 0.07.

The Southern Proper Motion Program. II. A Catalog at the South Galactic Pole

We describe the Yale/San Juan Southern Proper Motion (SPM) Catalog 1.0, which provides positions, absolute proper motions, and photographic BV photometry for 58,880 objects at the South Galactic pole. The sky coverage of the SPM Catalog 1.0 is about 720 deg2 in the magnitude range 5 < V < 18.5. About 55% of all catalog stars are randomly chosen, whereas the remainder contains numerous astrophysically interesting objects drawn from various lists and databases. The accuracy of positions and absolute proper motions is 40–150 mas and 3–8 mas yr-1, respectively, depending on the star's magnitude. The high-end astrometric accuracy applies to the stars brighter than V = 15. A great deal of effort was put into correcting positions and proper motions for the magnitude-dependent systematic errors. The catalog can be used for Galactic structure studies and deep CCD-frame astrometric calibration and as a database for stars, galaxies, and other objects at the south Galactic pole. The catalog is supplemented by calibrated CCD BV photometry in selected 13' × 13' areas.

The stellar populations of NGC 6822

view Abstract Citations (42) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Stellar Populations of NGC 6822 Wilson, Christine D. Abstract New CCD BV photometry is presented for blue and red stars in a large region of the Local Group dwarf irregular galaxy NGC 6822. The total reddening (foreground+internal) estimated from the median color of the blue plume is E(B- V) = 0.45. The slope of the luminosity function for blue stars with 17 < V <20 is 0.57+/- 0.10, in good agreement with previous studies for this and other galaxies. The OB associations are reidentified using an objective, automated group-finding algorithm. The properties of the OB associations in NGC 6822, such as mass and diameter, agree well with OB association properties in other galaxies. The red-to- blue supergiant ratio is found to be similar in NGC 6822, M33, and IC 1613, despite a range in metallicity of more than a factor often, which suggests that the red-to-blue ratio is not a sensitive function of metallicity. Finally, an attempt to determine the relative numbers of Wolf-Rayet stars and O start in NGC 6822 shows that the ratio N_WR_/N_OB_ can be constrained only to within a factor of 20, unless spectroscopic observations are available for a large sample of O stars. Publication: The Astronomical Journal Pub Date: October 1992 DOI: 10.1086/116327 Bibcode: 1992AJ....104.1374W Keywords: Blue Stars; Dwarf Galaxies; Irregular Galaxies; Local Group (Astronomy); O Stars; Stellar Spectrophotometry; Color-Magnitude Diagram; Data Reduction; Point Spread Functions; Stellar Luminosity; Supergiant Stars; Wolf-Rayet Stars; Astrophysics; GALAXIES: INDIVIUAL: NGC 6822; GALAXIES: STELLAR CONTENT full text sources ADS | data products SIMBAD (427) NED (1) Related Materials (1) Erratum: 1995AJ....109..449W

THE REDDENING TO THE GALAXY IC 342 FROM CCB BV PHOTOMETRY OF ITS BRIGHTEST STARS

ABSTRACT The intrinsic luminosity and distance to the low-galactic-latitude galaxy IC 342 have been a matter of some debate, largely due to the uncertainty in the estimates for the extinction. The dynamical influence of IC 342 on the Local Group may be more significant than has commonly been believed if a high reddening value and a low distance modulus to this galaxy is confirmed. In an effort to independently estimate the reddening for this galaxy, CCD BV photometry has been obtained for 117 stars brighter than V=22.0 mag in a field centered near a spiral arm in IC 342. The plume of main sequence and slightly evolved blue supergiant stars is detected at V=19.4 mag. However, the plume is centered at a color of (B-V)=0.54 mag. A comparison with similar color-magnitude diagram data for the brightest stars in IC 1613 suggests that these stars in IC 342 are reddened by E(B-V)=0.79 ± 0.05 mag. (AB=3.32 ± 0.21 mag). This value is in good agreement with the similarly high values suggested by the Burstein-Heiles conversions of Galactic HI column density to color excess, and especially by the recent measurement of the Balmer decrement of HII regions by McCall.

CCD BV photometry of the old rich open cluster king 2

We present preliminary results of CCD BV photometry of the old open cluster King 2. The values obtained for the main parameters are:E(B-V)=0.31, (m-M)0=13.78, metal content approximately solar, and age 6×109 yr. From the comparison with synthetic colour-mgnitude diagrams generated by models with overshoot we try to answer the question whether or not convective elements generated in the core can penetrate into the surrounding stable zone (separated by a discontinuity of molecular weight).