- ID:
- ivo://CDS.VizieR/J/PASP/122/288
- Title:
- UBVI_KC_ photometry in NGC 2309
- Short Name:
- J/PASP/122/288
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained CCD UBVI_KC_ photometry down to V~22.0 for the open cluster NGC 2309 and its surrounding field. Twenty three probable cluster members have been identified for the first time on the basis of sound photometric criteria. Because NGC 2309 is a relatively poor cluster projected onto a rich star field showing density fluctuations, the frequently used membership criteria based on stellar density profiles or proper motion measurements would not be enough to assess the star membership status if employed independently. We estimated a cluster radius of 7.9' and a radius at half the maximum of the cluster density profile of 1.7'. Based on the best fits of isochrones computed by the Geneva group to the cluster color-magnitude and color-color diagrams, previously shifted by the cluster reddening (E(B-V)=0.32) and distance (d=2.5kpc), we derived the cluster age (250Myr) and metallicity ([Fe/H]~0.0). If an 8.5kpc distance from the Sun to the center of the Galaxy is assumed, then NGC 2309 is found to be located just in front of the Perseus spiral arm.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/515/A16
- Title:
- UBVI light curves of NGC 884 variables
- Short Name:
- J/A+A/515/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. To improve our comprehension of the beta Cep stars, we studied the young open cluster NGC 884 to discover new B-type pulsators, besides the two known beta Cep stars, and other variable stars. An extensive multi-site campaign was set up to gather accurate CCD photometry time series in four filters (U, B, V, I) of a field of NGC 884. The images were calibrated and reduced to transform the CCD frames into interpretable light curves. Various variability indicators and frequency analyses were applied to detect variable stars in the field.
- ID:
- ivo://CDS.VizieR/J/AJ/106/220
- Title:
- UBVI photometry in Berkeley 31
- Short Name:
- J/AJ/106/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry on the Johnson UBV and on the Kron-Cousins VI systems are presented for 732 stars in and near Be 31, an open cluster located towards the galactic anticenter. The resultant color-magnitude diagrams indicate that the cluster is an old object. From the color-color diagram, the reddening and metallicity parameters are determined to be E(B-V) = 0.13 mag and [Fe/H] = -0.4. By comparing the cluster C-M diagrams with the VandenBerg isochrones, and by assuming a normal reddening law, a distance of 5.2 +/- 0.5 kpc and an age of 8 Gyr are derived.
- ID:
- ivo://CDS.VizieR/J/MNRAS/397/1073
- Title:
- UBVI photometry in NGC 2587
- Short Name:
- J/MNRAS/397/1073
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the Johnson U, B and V and Kron-Cousins I passbands for the open cluster NGC 2587. The sample consists of 4406 stars reaching down to V~21.0. We developed a new method to clean statistically the colour-magnitude diagrams. NGC 2587 appears to be a sparse, relatively bright open cluster, with a few tens of members projected on to a populous star field.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/56
- Title:
- UBVI photometry in NGC 6752
- Short Name:
- J/ApJ/783/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is devoted to photometric study of the Galactic globular cluster (GGC) NGC 6752 in UBVI, focusing on the multiplicity of its stellar population. We emphasize that our U passband is (1) narrower than the standard one due to its smaller extension blueward and (2) redshifted by ~300{AA} relative to its counterparts, such as the HST F336W filter. Accordingly, both the spectral features encompassed by it and photometric effects of the multiplicity revealed in our study are somewhat different than in recent studies of NGC 6752. Main sequence stars bluer in U-B are less centrally concentrated, as red giants are. We find a statistically significant increasing luminosity of the red giant branch (RGB) bump of {Delta}U{approx}0.2mag toward the cluster outskirts with no so obvious effect in V. The photometric results are correlated with spectroscopic data: the bluer RGB stars in U-B have lower nitrogen abundances. We draw attention to a larger width of the RGB than the blue horizontal branch (BHB) in U-B. This seems to agree with the effects predicted to be caused by molecular bands produced by nitrogen-containing molecules. We find that brighter BHB stars, especially the brightest ones, are more centrally concentrated. This implies that red giants that are redder in U - B, i.e., more nitrogen enriched and centrally concentrated, are the main progenitors of the brighter BHB stars. However, such a progenitor-progeny relationship disagrees with theoretical predictions and with the results on the elemental abundances in horizontal branch stars. We isolated the asymptotic giant branch clump and estimated the parameter {Delta}V_ZAHB_^clump^=0.98+/-0.12.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1565
- Title:
- UBVI photometry of Berkeley 17 and NGC 188
- Short Name:
- J/AJ/131/1565
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric UBVI CCD photometry is presented for NGC 188 and Berkeley 17. Color-magnitude diagrams (CMDs) are constructed and reach well past the main-sequence turnoff for both clusters. Cluster ages are determined by means of isochrone fitting to the cluster CMDs. These fits are constrained to agree with spectroscopic metallicity and reddening estimates. Cluster ages are determined to be 7.0+/-0.5Gyr for NGC 188 and 10.0+/-1.0Gyr for Berkeley 17, where the errors refer to uncertainties in the relative age determinations.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A39
- Title:
- UBVI photometry of Melotte 66
- Short Name:
- J/A+A/566/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiple generations of stars are routinely encountered in globular clusters, but no convincing evidence has been found in Galactic open clusters up to date. In this paper we use new photometric and spectroscopic data to search for multiple stellar population signatures in the old, massive open cluster, Melotte 66. The cluster is know to have a red giant branch wide in color, which could be an indication of metallicity spread. Also the main sequence is wider than what expected from photometric errors only. This evidence might be associated either with differential reddening or with binaries. Both hypothesis have, however, to be evaluated in detail before recurring to the presence of multiple stellar populations. New, high-quality, CCD UBVI photometry have been acquired to this aim, together with high-resolution spectroscopy of seven clump stars, complemented with literature data, thus doubling the number of clump stars member of the cluster for which high-resolution spectroscopy is available. All this new material is carefully analyzed in search for any manifestation, either spectroscopic or photometric, of multiple populations among the cluster stars. Our photometric study confirms that the width of the main sequence close to the turn off point is entirely accounted for by binary stars and differential reddening, with no need to advocate more sofisticated scenarios, like metallicity spread or multiple main sequences. By constructing synthetic color-magnitude diagrams, we infer that the binary fraction has to be as large as 30%, and their mass ratio in the range 0.6-1.0. As a by-product of our simulations, we provide new estimates of the cluster fundamental parameters. We measure a reddening E(B-V)=0.15+/-0.02, and confirm the presence of a marginal differential reddening. The distance to the cluster is 4.7^+0.2^_-0.1_kpc, and the age is 3.4+/-0.3Gyr, somewhat younger and better constrained than previous estimates. Our detailed abundance analysis reveals that, overall, Melotte 66 looks like a typical object of the old thin disk population, with no significant spread in any of the chemical species we could measure. Finally, we perform a photometric study of the blue straggler star population, and argue that their number in Melotte 66 has been significantly over-estimated in the past. The analysis of their spatial distribution supports the scenario they are most probably primordial binaries.
- ID:
- ivo://CDS.VizieR/J/A+A/469/529
- Title:
- UBVI photometry of NGC 6864
- Short Name:
- J/A+A/469/529
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carry out and analyze new multi-color photometry of the Galactic globular cluster (GC) M75 in UBVI and focus on the brighter sequences of the color-magnitude diagram (CMD), with particular emphasis on their location in U-based CMD. Specifically, we study the level both of the horizontal (HB) and red giant branches (RGB) relative to the main-sequence turnoff (TO) in the U magnitude. Along with the presented photometry of M75, we use our collection of photometric data on GCs belonging to the metal-poor range, [Fe/H]zw<-1.1dex, obtained from observations with different equipment, but calibrated by standard stars situated in the observed cluster fields. We confirm our earlier finding, and extend it to a larger magnitude range. We demonstrate that Delta(U_TO_^BHB^) expressing the difference in U magnitude between the TO point and the level of the blue HB, near its red boundary, of the metal-poor GCs observed with the EMMI camera of the NTT/ESO telescope is about 0.4-0.5mag smaller as compared to GCs observed with the 100" telescope and 1.3m Warsaw telescope of the Las Campanas Observatory. At the same time, Delta(U_TO_^RGB^), the difference in U magnitude between the TO and RGB inflection (brightest) points, does not show such an apparent dependence on the characteristics of U filters used, but it depends on cluster metallicity. We have shown, for the first time, the dependence of the parameter Delta(U_TO_^RGB^) on [Fe/H] and have estimated its analytical expression, by assuming a linear relation between the parameter and metallicity. Its slope, Delta(U_TO_^RGB^)/Delta[Fe/H]~1.2mag/dex, is approximately a factor of two steeper than that of the dependence of the RGB bump position in the V magnitude on metallicity. The asymptotic giant branch (AGB) clump and features of the RGB luminosity function (LF) of M75 are also discussed. The observations were made on 3 nights, 9-12 October 1998, with the 1.3m Warsaw telescope.
- ID:
- ivo://CDS.VizieR/J/A+A/466/931
- Title:
- UBVI photometry of NGC 1901
- Short Name:
- J/A+A/466/931
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations indicate that present-day star formation in the Milky Way disk takes place in stellar ensembles or clusters rather than in isolation. Bound, long-lived stellar groups are known as open clusters. They gradually lose stars and are severely disrupted in their final evolutionary stages, leaving an open cluster remnant made up of a few stars. In this paper, we study in detail the stellar content and kinematics of the poorly populated star cluster NGC 1901. This object appears projected against the Large Magellanic Cloud. The aim of the present work is to derive the current evolutionary status, binary fraction, age, and mass of this stellar group. These are fundamental quantities to compare with those from N-body models in order to study the most general topic of star cluster evolution and dissolution. The analysis is performed using wide-field photometry in the UBVI pass-band, proper motions from the UCAC.2 catalog, and 3 epochs of high-resolution spectroscopy, as well as results from extensive N-body calculations. The star group NGC 1901 is found to be an ensemble of solar metallicity stars, 400+/-100Myr old, with a core radius of 0.23pc, a tidal radius of 1.0pc, and a location at 400+/-50pc from the Sun. Out of 13 confirmed members, only 5 single stars have been found. Its estimated present-day binary fraction is at least 62%. The calculated heliocentric space motion of the cluster is not compatible with possible membership in the Hyades stream. Our results show that NGC 1901 is a clear prototype of an open cluster remnant characterized by a high value of the binary fraction and a significant depletion of low-mass stars. In light of numerical simulations, this is compatible with NGC 1901 being what remains of a larger system initially made of 500-750 stars.
- ID:
- ivo://CDS.VizieR/J/AJ/108/585
- Title:
- UBVI photometry of NGC 6791
- Short Name:
- J/AJ/108/585
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated the reddening and metallicity of NGC 6791 using photoelectric and Charge Coupled Devices (CCD) photometry at the KPNO 0.9m telescope. The reddenings to 31 photoelectrically measured stars in the direction of the cluster were determined individually yielding a mean E(B-V)=0.10+/-0.02. Broadband UBVI CCD images were taken with a 512x512 CCD and included deep frames on the center, plus a 3x3 mosaic of the cluster.
