- 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.
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Search Results
- 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/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)
- 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/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/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.
