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7071. UBVI photometry in NGC 2587
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.
7072. UBVI photometry in NGC 6752
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.
7073. UBVI photometry in NGC 458
ID:
ivo://CDS.VizieR/J/A+A/400/917
Title:
UBVI photometry in NGC 458
Short Name:
J/A+A/400/917
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new photometry of the Small Magellanic Cloud star cluster NGC 458 in UBVI filters. We determine the reddening E(B-V)=0.04+/-0.02. By comparison with the isochrones by Bertelli et al. (1994, Cat. <J/A+AS/106/275>) we derive an age of ~140Myr. Three candidate blue straggler stars are proposed. The evolved "blue loop'' stars of NGC 458 have masses between 4 and 5M_{sun}_ and are hotter than model predictions.
7074. UBVI Photometry in 7 open clusters
ID:
ivo://CDS.VizieR/J/A+AS/94/73
Title:
UBVI Photometry in 7 open clusters
Short Name:
J/A+AS/94/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
7075. UBVI photometry in 4 open clusters
ID:
ivo://CDS.VizieR/J/AJ/113/1723
Title:
UBVI photometry in 4 open clusters
Short Name:
J/AJ/113/1723
Date:
21 Oct 2021
Publisher:
CDS
Description:
Ages and distance moduli for the open clusters NGC 2204, Berkeley 39, NGC 2477, and Melotte 66 are constrained by comparing the theoretical models developed by Bertelli et al. (1994, Cat. J/A+AS/106/275) to the observed cluster color-magnitude diagrams which are based on deep CCD photometry. Out of a set of comparison models, no single isochrone was superior to the others in describing an observed color-magnitude diagram. Thus, a best fitting model was selected based not only on the match to an observed color-magnitude diagram, but also on the isochrone's agreement with adopted values for the cluster's metallicity and reddening. The range of otherwise acceptable models help quantify the age and distance modulus uncertainty of each cluster. Based on the best fitting models: * NGC 2204 is 1.6^+0.9^_-0.3_Gyr old with (m-M)_o_=13.0^+0.5^_-0.4_ , * Berkeley 39 has an age of 6^+2^_-1_Gyr with (m-M)_o_=12.9+/-0.2, * NGC 2477 is 1^+0.3^_-0.2_Gyr old with (m-M)_o=10.5^+0.4^_-0.3_ , and * Melotte 66 has an age of 4+/-1Gyr with (m-M)_o_=13.2^+0.3^_-0.1_.
7076. UBVI photometry of Berkeley 17 and NGC 188
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.
7077. UBVI photometry of GCs in the Fornax galaxy cluster
ID:
ivo://CDS.VizieR/J/ApJ/763/40
Title:
UBVI photometry of GCs in the Fornax galaxy cluster
Short Name:
J/ApJ/763/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present wide-field multiband photometry of globular cluster (GC) systems in NGC 1399, NGC 1404, and NGC 1387 located in the central region of the Fornax galaxy cluster. Observation was carried out through U, B, V, and I bands, which marks one of the widest and deepest U-band studies on extragalactic GC systems. The present U-band photometry enables us to significantly reduce the contamination by a factor of two for faint sources (V_0_~23.5). The main results based on some 2000 GC candidates around NGC 1399, NGC 1404, and NGC 1387 are as follows: (1) the GC system in each galaxy exhibits bimodal color distributions in all colors examined, but the shape of color histograms varies systematically depending on colors; (2) NGC 1399 shows that the mean colors of both blue and red GCs become bluer with increasing galactocentric radius; (3) NGC 1399 shows overabundance of GCs in the directions of NGC 1404 and NGC 1387, indicating their ongoing interactions; and (4) NGC 1399 also exhibits a ~0.'5 offset between the center of the inner GC distribution and the galaxy's optical center, suggesting that NGC 1399 is not yet dynamically relaxed and may be undergoing merger events.
7078. UBVI photometry of Melotte 66
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.
7079. UBVI photometry of NGC4337
ID:
ivo://CDS.VizieR/J/MNRAS/441/L36
Title:
UBVI photometry of NGC4337
Short Name:
J/MNRAS/441/L36
Date:
21 Oct 2021
Publisher:
CDS
Description:
Galactic open clusters do not survive long in the high-density regions of the inner Galactic disc. Inside the solar ring only 11 open clusters are known with ages older than 1Gyr. We show here, basing on deep, high-quality photometry, that NGC 4337, contrary to earlier findings, is indeed an old open cluster. The cluster is located very close to the conspicuous star cluster Trumpler 20, as well misclassified in the past, and that has received so much attention in recent years. NGC 4337 shows a significant clump of He-burning stars which was not detected previously. Its beautiful colour-magnitude diagram is strikingly similar to the one of the classical old open clusters IC 4651, NGC 752, and NGC 3680, and this suggests similar age and composition. A spectroscopic study is much needed to confirm our findings. This, in turn, would also allow us to better define the inner disc radial abundance gradient and its temporal evolution. To this aim, a list of clump star candidates is provided.
7080. UBVI photometry of NGC 6864
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.