- 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.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/other/BASI/29.53
- Title:
- UBVI photometry in Berkeley 32
- Short Name:
- J/other/BASI/29.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new CCD photometry of the distant old open star cluster Berkeley 32 in Johnson V and Cousins I passbands. A total of about 3200 stars have been observed in a field of about 13'x13'. The colour-magnitude diagram (CMD) in V, (V-I) has been generated down to V=22mag. A broad but well defined main sequence is clearly visible. Some blue stragglers, a well developed subgiant branch and a Red Clump are also seen. By fitting isochrones to this CMD as well as to other CMDs available in the literature, and using the Red Clump location, the reddening, distance and age of the star cluster have been determined. The cluster has a distance of about 3.3kpc, its radius is about 2.4pc; the reddening E(B-V) is 0.08 mag and the age is about 6.3Gyr. By comparison with theoretical isochrones, a metallicity of [Fe/H]~-0.2dex has been estimated.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A70
- Title:
- UBVI photometry in 3 globular clusters
- Short Name:
- J/A+A/573/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric analysis of the external regions of three Galactic Globular Clusters: NGC 6121, NGC 6397 and NGC 6752. The main goal is the characterization of the multiple stellar populations along the main sequence (MS) and the study of the radial trend of the different populations hosted by the target clusters. The data have been collected using FORS2 mounted at the ESO/VLT@UT1 telescope in UBVI filters. From these data sets we extracted high-accuracy photometry and constructed color-magnitude diagrams. We exploit appropriate combination of colors and magnitudes which are powerful tools to identify multiple stellar populations, like B versus U-B and V versus c_U,B,I_=(U-B)-(B-I) CMDs. We confirm previous findings of a split MS in NGC 6752 and NGC 6121. Apart from the extreme case of omega Centauri, this is the first detection of multiple MS from ground-based photometry. For NGC 6752 and NGC 6121 we compare the number ratio of the blue MS to the red MS in the cluster outskirts with the fraction of first and second generation stars measured in the central regions. There is no evidence for significant radial trend. The MS of NGC 6397 is consistent with a simple stellar population. We propose that the lack of multiple sequences is due both to observational errors and to the limited sensitivity of U,B,V,I photometry to multiple stellar populations in metal-poor GCs. Finally, we compute the helium abundance for the stellar populations hosted by NGC 6121 and NGC 6752, finding a mild ({Delta}Y~0.02) difference between stars in the two sequences.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/194
- Title:
- UBVI photometry in NGC 1252
- Short Name:
- J/MNRAS/434/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- If stars form in clusters but most stars belong to the field, understanding the details of the transition from the former to the latter is imperative to explain the observational properties of the field. Aging open clusters are one of the sources of field stars. The disruption rate of open clusters slows down with age but, as an object gets older, the distinction between the remaining cluster or open cluster remnant (OCR) and the surrounding field becomes less and less obvious. As a result, finding good OCR candidates or confirming the OCR nature of some of the best candidates still remain elusive. One of these objects is NGC 1252, a scattered group of about 20 stars in Horologium. Here we use new wide-field photometry in the UBVI passbands, proper motions from the Yale/San Juan SPM 4.0 catalogue and high-resolution spectroscopy concurrently with results from N-body simulations to decipher NGC 1252's enigmatic character. Spectroscopy shows that most of the brightest stars in the studied area are chemically, kinematically and spatially unrelated to each other. However, after analysing proper motions, we find one relevant kinematic group. This sparse object is relatively close (~1kpc), metal poor and is probably not only one of the oldest clusters (3Gyr) within 1.5kpc from the Sun but also one of the clusters located farthest from the disc, at an altitude of nearly -900pc. That makes NGC 1252 the first open cluster that can be truly considered a high Galactic altitude OCR: an unusual object that may hint at a star formation event induced on a high Galactic altitude gas cloud. We also conclude that the variable TW Horologii and the blue straggler candidate HD 20286 are unlikely to be part of NGC 1252. NGC 1252 17 is identified as an unrelated, Population II cannonball star moving at about 400km/s.
- 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/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/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.
- 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_.
- 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/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.
