- ID:
- ivo://CDS.VizieR/J/A+A/497/371
- Title:
- UBVI photometry of NGC 3201
- Short Name:
- J/A+A/497/371
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper aims at further studying one of the nearby Galactic globular clusters (GCs), NGC 3201. It is known to experience notable irregular variability of reddening across its face. By relying on our previous studies and findings and by developing them, we focus on the brighter sequences of the color-magnitude diagram (CMD) and on the cluster's characteristics. We carried out and analyzed new multi-color photometry of NGC 3201 in UBVI reaching below the turnoff point in all passbands in a fairly large cluster field, about 14'x14'. To achieve more reliable results and conclusions, we reduced the negative impact of the irregularly varying reddening and contamination by field stars. With this aim we first estimated mean reddening in different zones of the studied cluster field and then took its variations into account, by reducing them to the same level. We estimated metallicity of NGC 3201 using a new metallicity indicator related to U-based CMDs, recently proposed by us. We find [Fe/H]zw=-1.54+/-0.12dex, which falls between extreme estimates of the cluster's metallicity obtained using different methods or indicators. Also, the location of the RGB bump on the branch corresponds to [Fe/H]zw=-1.46+/-0.15dex. We isolate 73 probable blue straggler (BS) candidates, the largest population found in NGC 3201 so far. They are more centrally concentrated than the lower red giants at the 99.2% level. Their position in the two-color diagram assumes that presumably none of them belongs to BSa of collisional origin. The luminosity function (LF) of the RGB and its features in the low part of the branch are examined and discussed. We also resolve some of the contradictory results of previous publications.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/516/A23
- Title:
- UBVI Photometry of NGC 1261
- Short Name:
- J/A+A/516/A23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work studies in more detail the stellar population, including its photometric properties and characteristics, in the rarely studied southern Galactic globular cluster NGC 1261. We focus on the brighter sequences of the cluster's color-magnitude diagram (CMD). Like in our previous works, we rely upon photometry in several passbands to achieve more reliable results and conclusions. We carried out and analyzed new multi-color photometry of NGC 1261 in UBVI reaching below the turnoff point in all passbands in a fairly extended cluster field, about 14'x14'. We found several signs of the inhomogeneity ("multiplicity") in the stellar population. The most prominent of them are: (1) the dependence of the radial distribution of sub-giant branch (SGB) stars in the cluster on their U magnitude, with brighter stars less centrally concentrated at the 99.9% level than their fainter counterparts; (2) the dependence of the location of red giant branch (RGB) stars in the U-(U-B) CMD on their radial distance from the cluster center, with the portion of stars bluer in the (U-B) color increasing towards the cluster outskirts. Additionally, the radial variation of the RGB luminosity function in the bump region is suspected. We assume that both the SGB stars brighter in the U and the RGB stars bluer in the (U-B) color are probably associated with blue horizontal branch stars, because of a similarity in their radial distribution in the cluster. We estimated the metallicity of NGC 1261 from the slope of the RGB in U-based CMDs and the location of the RGB bump on the branch. These metallicity indicators give [Fe/H]_ZW_=-1.34+/-0.16dex and [Fe/H]_ZW_=-1.41+/-0.10dex, respectively. We isolated 18 probable blue straggler candidates. They are more centrally concentrated than the lower red giants of comparable brightness at the 97.9% level. Their photometric characteristics imply that their majority is not consistent with the collisional origin. We also reliably isolated the asymptotic giant branch (AGB) clump and estimated the parameter Delta V_{ZAHB}_^{clump}^=1.01+/-0.06, that is the difference between the V-levels of the zero age HB and the clump.
- ID:
- ivo://CDS.VizieR/J/A+A/385/471
- Title:
- UBVI photometry of NGC 7036 and NGC 7772
- Short Name:
- J/A+A/385/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD UBVI observations obtained in the field of the two previously unstudied dissolving open cluster candidates NGC 7036 and NGC 7772. Our analysis suggests that both the objects are Open Cluster Remnants (OCR). NGC 7036 is an open cluster remnant with a core radius of about 3-4 arcmin. We derive for the first time estimates of its fundamental parameters. We identify 17 likely members that define a group of stars at 1kpc from the Sun, with a low reddening E(B-V)~0.1, and with an age of about 3-4Gyr. As for NGC 7772, we identify 14 likely members, that define a group of stars with a very low reddening (E(B-V)~0.03), are 1.5Gyr old and are located about 1.5kpc from the Sun.
- ID:
- ivo://CDS.VizieR/J/A+A/387/479
- Title:
- UBVI photometry of NGC 133 and NGC 1348
- Short Name:
- J/A+A/387/479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD UBVI observations obtained in the field of the previously unstudied northern open clusters NGC 133 and NGC 1348. We argue that NGC 133 is a heavily contaminated cluster, for which we identify 13 candidate members down to V=14.50mag on the basis of the position in the two-color Diagram. Membership has been checked against proper motions from Tycho 2, whenever available. The cluster turns out to have a reddening E(B-V)=0.60+/-0.10mag, to be 630+/-150pc distant from the Sun, and to have an age less than 10Myrs. NGC 1348 is a more reddened clusters (E(B-V)=0.85+/-0.15mag) for which we isolate 20 members. The cluster lies at a distance of 1.9+/-0.5kpc away from the Sun, and has an age greater than 50Myrs. Observations were carried out with the AFOSC camera at the 1.82m Copernico telescope of Cima Ekar (Asiago, Italy), in the photometric night of December 18, 2001.
- ID:
- ivo://CDS.VizieR/J/A+A/374/504
- Title:
- UBVI photometry of NGC 7654 (M52)
- Short Name:
- J/A+A/374/504
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD UBVIc photometry in a wide field around the open cluster NGC 7654 has been carried out for ~17860 stars, down to V~20. The reddening across the cluster region is found to be variable with E(B-V) from 0.46mag to 0.80mag. The cluster is situated at a distance of 1380+/-70pc. The colour magnitude diagrams show a large age spread in the ages. Star formation was biased towards relatively higher masses during the early phase of star formation whereas most of the low mass stars of the cluster were formed during the later phase. The star formation seems to have been a gradual process that proceeded sequentially in mass and terminated with the formation of most massive stars. The present data do not support a uniform mass function (MF) for different regions in the cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/408/1147
- Title:
- UBVI photometry of 4 open clusters
- Short Name:
- J/MNRAS/408/1147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the Johnson UBV and Kron-Cousins I systems down to V~22.0 for the open clusters NGC 2311, Trumpler 6, NGC 2432 and BH 54 and their surrounding fields. Trumpler 6 and BH 54 have never been studied before and so we provide, for the first time, estimates of their fundamental parameters. We obtained colour-magnitude diagrams (CMDs) and colour-colour diagrams cleaned from field star contamination by statistically subtracting stars in terms of spatial density, magnitude and colour distributions. Cluster angular radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. Using the cleaned CMDs and colour-colour diagrams, we applied sound photometric membership criteria to discriminate cluster members from interloper field stars. The interstellar extinction across the cluster fields derived from the 100-{mu}m dust emission full-sky maps can be considered uniform within the quoted uncertainties. The E(B-V) and E(V-I) colour excesses and the apparent distance moduli of the clusters were estimated from the fit of the zero-age main-sequence to the colour-colour diagrams and CMDs, respectively. Cluster ages were determined from the comparison of the four clusters' CMDs with solar metallicity theoretical isochrones of the Geneva group. All the clusters were found to be moderately young objects, their ages ranging between 60 and 250Myr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/2720
- Title:
- UBVI photometry of 5 open clusters
- Short Name:
- J/MNRAS/402/2720
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained CCD UBVI_KC_ photometry down to V~21.0 for the open clusters Berkeley 26, Czernik 27, Melotte 72, NGC 2479 and BH 37. The latter has never been studied before. Cluster stellar density profiles were obtained from star counts in appropriate-sized boxes distributed throughout the entire observed fields. Based on different measured indices, we estimate the ages of Berkeley 26, Melotte 72 and NGC 2479. On the other hand, we indicate possible solutions for the cluster fundamental parameters by matching theoretical isochrones which reasonably reproduce the main cluster features in their colour-magnitude diagrams. In the case of NGC 2479, the cluster E(BV) and E(VI) colour excesses and apparent distance modulus were estimated from the fit of the zero-age main sequence to the colour-colour and colour-magnitude diagrams, respectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/502
- Title:
- UBVI photometry of 7 open clusters
- Short Name:
- J/MNRAS/428/502
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New photometric material is presented for six outer disc supposedly old, Galactic star clusters: Berkeley 76, Haffner 4, Ruprecht 10, Haffner 7, Haffner 11 and Haffner 15, which are projected against the rich and complex Canis Major overdensity at 225{deg}<=l<=248{deg}, -7{deg}b<=-2{deg}. This CCD data set, in the UBVI passbands, is used to derive their fundamental parameters, in particular age and distance. Four of the program clusters turn out to be older than 1Gyr. This fact makes them ideal targets for future spectroscopic campaigns aiming at deriving their metal abundances. This, in turn, contributes to increase the number of well-studied outer disc old open clusters. Only Haffner 15, previously considered an old cluster, is found to be a young, significantly reddened cluster, member of the Perseus arm in the third Galactic quadrant. As for Haffner 4, we suggest an age of about half a Gyr. The most interesting result we found is that Berkeley 76 is probably located at more than 17kpc from the Galactic centre, and therefore is among the most peripherical old open clusters so far detected. Besides, for Ruprecht 10 and Haffner 7, which were never studied before, we propose ages larger than 1Gyr. All the old clusters of this sample are scarcely populated and show evidence of tidal interaction with the Milky Way, and are therefore most probably in advanced stages of dynamical dissolution.
- ID:
- ivo://CDS.VizieR/J/A+A/536/A101
- Title:
- UBVI photometry towards (l=314,b=0)
- Short Name:
- J/A+A/536/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spiral structure of the Milky Way is nowadays receiving renewed attention thanks to the combined efforts of observational campaigns in different wavelength regimes, from the optical to the radio. We start in the paper the exploration of a number of key sectors (line of sights) in the inner Milky Way, where the spiral structure is still poorly known. We search for density enhancements of young stars that might plausibly be associated with spiral structure. To this aim we collect sufficiently wide-field UBVI photometry to allow us to probe in statistical sense the distribution in reddening and distance of young stars in the field. The intensive usage of U-band photometry - although heavily demanding in terms of observational efforts - ensures robust determination of reddening and hence distance for stars of spectral type earlier than A0, which are well-known spiral arm tracers, even though no spectroscopic information are available. The fields we use are large enough to include in most cases well-studied Galactic clusters, which we use as bench-marks to assess the quality and standardisation of the data, and to validate our method. We focus in this paper on the line of sight to the Galactic longitude l=314{deg}, where previous surveys already detected H{alpha} emitters at different standard of rest velocities, and hence distances. The difficulty, however, to translate velocity into distance make predictions on the spiral structure quite vague. First of all, we made exhaustive tests to show that our data-set is in the standard system, and calibrated our method using the two open clusters NGC 5617 and Pismis 19 which happen to be in the field, and for which we found estimates of the basic parameters in full agreement with the literature. We then applied the method to the general field stars and detected signatures of three different groups of stars, evenly distributed across the field of view, at 1.5^+0.5^_-0.2_, 2.5^+0.3^_-0.5_, and 5.1^+1.5^_-1.1_kpc, respectively. These distances are compatible with the location of the nowadays commonly accepted description of the Carina-Sagittarius and Scutum-Crux arms, at heliocentric distance of ~2 an 5kpc, respectively. As a consequence, we consider these groups to be good candidates to trace the location of these two inner arms. In line with previous studies, this investigation demonstrates once again how powerful the use of U-band photometry is to characterize ensembles of young stars, and make predictions on the spiral structure of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1275
- Title:
- UBV photometry in 5 fields of the LMC
- Short Name:
- J/AJ/116/1275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBV photometry of four fields within Shapley Constellation III and one field on the edge of the shell. Our fields cover roughly 20% of the region, mostly in the southern half. Determinations are made of ages of the fields, the star formation densities, and the initial mass function (IMF) slopes.
