共查询到20条相似文献,搜索用时 628 毫秒
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Annapurni Subramaniam Bhuwan Chandra Bhatt 《Monthly notices of the Royal Astronomical Society》2007,377(2):829-834
We present a UBV CCD photometric study of four open clusters, NGC 7245, King 9, IC 166 and King 13, located between l = 90° and 135°. All are embedded in a rich Galactic field. NGC 7245 and King 9 are close together in the sky and have similar reddenings. The distances and ages are: NGC 7245, 3.8 ± 0.35 kpc and 400 Myr; King 9 (the most distant cluster in this quadrant), 7.9 ± 1.1 kpc and 3.0 Gyr. King 13 is 3.1 ± 0.3 kpc distant and 300 Myr old. King 9 and IC 166 (4.8 ± 0.5 kpc distant and 1 Gyr old) may be metal-poor clusters ( Z = 0.008) , as estimated from isochrone fitting. The average value of the distance of young clusters from the Galactic plane in the above longitude range and beyond 2 kpc (−47 ± 16 pc, for 64 clusters) indicates that the young disc bends towards the southern latitudes. 相似文献
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G. Carraro † G. Baume R. A. Vázquez A. Moitinho D. Geisler 《Monthly notices of the Royal Astronomical Society》2005,362(2):649-656
We present the first BVI CCD photometry to V = 22.0 of four fields centred on the region of the southern Galactic star clusters Ruprecht 61, Czernik 32, NGC 2225 and 2262 and of four displaced control fields. These clusters have never been studied before, and we provide for the first time estimates of their fundamental parameters, specifically radial extent, age, distance and reddening. We find that the four clusters are all of intermediate age (around 1 Gyr), close to the Sun and possess lower than solar metal abundance. 相似文献
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Ferdinando Patat Giovanni Carraro 《Monthly notices of the Royal Astronomical Society》2001,325(4):1591-1602
We report on the first UBVRI CCD photometry of three poorly known star clusterings in the region of η Carinae: Bochum 9, 10 and 11. We find that they are young, rather poor, loose open clusters.
We argue that Bochum 9 is probably a small and loose open cluster with about 30 probable members having E ( B − V )=0.63±0.08 , located 4.6 kpc far from the Sun, beyond the Carina spiral arm.
Similarly, Bochum 10 is a sparse aggregate with 14 probable members having E ( B − V )=0.47±0.05 and at a distance of 2.7 kpc from the Sun.
Finally, Bochum 11 is a less than 4×106 yr old cluster for which we identify 24 members. It has a reddening E ( B − V )=0.58±0.05 , and lies between Bochum 10 and 9, at 3.5 kpc from the Sun. We propose that in the field of the cluster some stars might be pre-main-sequence candidates. 相似文献
We argue that Bochum 9 is probably a small and loose open cluster with about 30 probable members having E ( B − V )=0.63±0.08 , located 4.6 kpc far from the Sun, beyond the Carina spiral arm.
Similarly, Bochum 10 is a sparse aggregate with 14 probable members having E ( B − V )=0.47±0.05 and at a distance of 2.7 kpc from the Sun.
Finally, Bochum 11 is a less than 4×10
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Annabel Cartwright Anthony P. Whitworth 《Monthly notices of the Royal Astronomical Society》2009,392(1):341-345
We have previously reported a measure which both quantifies and distinguishes between a (relatively smooth) large-scale radial density gradient and multiscale (fractal) subclustering. Here, we extend the applicability of to clusters which deviate significantly from an overall circular shape.
varies systematically as clusters assume a more elongated shape, and it is therefore possible to correct for the effect, if the elongation of the cluster is also quantified. therefore remains a useful and robust analytical technique for classifying and quantifying the internal structure of star clusters, even when their overall shape is far from circular.
The corrections required are small for individual clusters which are not extremely elongated (not more than three times longer than they are wide) of the same order as the uncertainty in the value of for a particular cluster type. We therefore recommend that no correction be applied to the calculation of for individual clusters, unless they are more than three times longer than their width, but that correction for elongation be applied when is used for statistical analyses of large numbers of observed or simulated clusters. 相似文献
varies systematically as clusters assume a more elongated shape, and it is therefore possible to correct for the effect, if the elongation of the cluster is also quantified. therefore remains a useful and robust analytical technique for classifying and quantifying the internal structure of star clusters, even when their overall shape is far from circular.
The corrections required are small for individual clusters which are not extremely elongated (not more than three times longer than they are wide) of the same order as the uncertainty in the value of for a particular cluster type. We therefore recommend that no correction be applied to the calculation of for individual clusters, unless they are more than three times longer than their width, but that correction for elongation be applied when is used for statistical analyses of large numbers of observed or simulated clusters. 相似文献
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S. L. Casewell R. F. Jameson P. D. Dobbie 《Monthly notices of the Royal Astronomical Society》2006,365(2):447-453
We present the results of a survey of the Coma Berenices open star cluster (Melotte 111), undertaken using proper motions from the USNO-B1.0 (United States Naval Observatory) and photometry from the Two-Micron All-Sky Survey (2MASS) Point Source catalogues. We have identified 60 new candidate members with masses in the range 1.007 < M < 0.269 M⊙ . For each we have estimated a membership probability by extracting control clusters from the proper motion vector diagram. All 60 are found to have greater than 60 per cent probability of being members, more than doubling the number of known cluster members. The new luminosity function for the cluster peaks at bright magnitudes, but is rising at K ≈ 12 , indicating that it is likely that lower mass members may exist. The mass function also supports this hypothesis. 相似文献
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M. Patel R. D. Oudmaijer J. S. Vink J. C. Mottram B. Davies 《Monthly notices of the Royal Astronomical Society》2006,373(4):1641-1647
We aim to characterize the current status of knowledge on the accuracy of open-cluster parameters such as the age, reddening and distance. These astrophysical quantities are often used to study the global characteristics of the Milky Way down to the very local stellar phenomena. In general, the errors of these quantities are neglected or set to some kind of heuristic standard value. We attempt to give some realistic estimates for the accuracy of available cluster parameters by using the independently derived values published in the literature. In total, 6437 individual estimates for 395 open clusters were used in our statistical analysis. We discuss the error sources depending on theoretical as well as observational methods and compare our results with those parameters listed in the widely used catalogue by Dias et al. In addition, we establish a list of 72 open clusters with the most accurate known parameters which should serve as a standard table in the future for testing isochrones and stellar models. 相似文献
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Ronnie Hoogerwerf 《Monthly notices of the Royal Astronomical Society》2000,313(1):43-65
The Hipparcos Catalogue contains members of nearby OB associations brighter than 12th magnitude in V . However, membership lists are complete only to magnitude V =7.3. In this paper we discuss whether proper motions listed in the 'Astrographic Catalogue+Tycho' reference catalogue (ACT) and the Tycho Reference Catalogue (TRC), which are complete to V ∼10.5 mag, can be used to find additional association members. Proper motions in the ACT/TRC have an average accuracy of ∼3 mas yr−1 . We search for ACT/TRC stars which have proper motions consistent with the spatial velocity of the Hipparcos members of the nearby OB associations already identified by de Zeeuw et al. These stars are first selected using a convergent-point method, and then subjected to further constraints on the proper-motion distribution, magnitude and colour to narrow down the final number of candidate members. Monte Carlo simulations show that the proper-motion distribution, magnitude, and colour constraints remove ∼97 per cent of the field stars, while at the same time retain more than 90 per cent of the cluster stars.
The procedure has been applied to five nearby associations: the three subgroups of Sco OB2, plus Per OB3 and Cep OB6. In all cases except Cep OB6, we find evidence for new association members fainter than the completeness limit of the Hipparcos Catalogue. However, narrow-band photometry and/or radial velocities are needed to pinpoint the cluster members, and to study their physical characteristics. 相似文献
The procedure has been applied to five nearby associations: the three subgroups of Sco OB2, plus Per OB3 and Cep OB6. In all cases except Cep OB6, we find evidence for new association members fainter than the completeness limit of the Hipparcos Catalogue. However, narrow-band photometry and/or radial velocities are needed to pinpoint the cluster members, and to study their physical characteristics. 相似文献
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