- 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_.
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Search Results
- 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/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.
- 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.
- 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/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/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/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.