Membership of the open cluster NGC 2264.

Vasilevskis, S.; Sanders, W. L.; Balz, A. G. A.

doi:10.1086/109820

Cited by 48 publications

(49 citation statements)

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“…If we assume a distance of 760 pc (Park et al 1997) for NGC 2264 a star with a projected tangential velocity of 1 km s −1 moves 4.5 within 1 Myr. The observed velocity dispersion of cluster members in the proper motion study by Vasilevskis et al (1965) is somewhat larger. For the stars with a cluster membership probability of more than 0.95 they observed a dispersion (one sigma) in the proper motions per century (µ x , µ y ) of 0.…”

Section: Spatial Distribution Of Young and Old Starsmentioning

confidence: 76%

Rotational evolution of low mass stars: The case of NGC 2264

Lamm¹,

Mundt²,

Bailer‐Jones³

et al. 2005

A&A

115

218

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Abstract. Our study is based on an extensive photometric monitoring program in the young (2-4 Myr) open cluster NGC 2264 by Lamm et al. (2004a). This program resulted in a sample of 405 periodic variables which are most likely pre-main sequence (PMS) members of the cluster. The periodic variability of these stars results from the rotational modulation of the light by stellar spots. In this paper we investigate the rotation period evolution of young stars. This is done by comparing the period distribution of the older NGC 2264 with that of the younger Orion Nebular Cluster (ONC, age: ∼1 Myr) which is known from the literature. The age ratio between the two clusters was estimated on the basis of PMS models to be about 2 +0.75 −0.5 . We find that the period distribution of NGC 2264 is similar in form to the ONC but shifted to shorter periods. In both clusters the period distribution depends strongly on the mass and it is bimodal for higher mass stars with M > ∼ 0.25 M while it is unimodal for lower mass stars with M < ∼ 0.25 M . In addition the lower mass stars rotate much faster on average than the higher mass stars. Quantitative comparison between the period distributions of both clusters suggests that a large fraction (about 80%) of stars have spun up from the age of the ONC to the age of NGC 2264. Based on this estimate and the estimated age ratio between the two clusters we find that the average spin up by a factor of 1.5−1.8 from the age of the ONC to the age of NGC 2264 is consistent with a decreasing stellar radius and conservation of angular momentum, for most stars. However, within NGC 2264 we did not find any significant spin up from the younger to older stars in the cluster. We also found indications for some ongoing disk-locking in NGC 2264, in particular for the higher mass stars. Our analysis of the period distribution suggests that about 30% of the higher mass stars in NGC 2264 could be magnetically locked into co-rotation with their inner disk. In the case of the lower mass stars, disk-locking seems to be less important for the rotational evolution of the stars. This interpretation is supported by the analysis of the stars' Hα emission. This analysis indicates that the locking period of the higher mass stars is about P = 8 days. For the lower mass stars this analysis indicates a locking period of about 2-3 days. We argue that the latter stars are probably not "completely" locked to their disk and propose an evolution scenario for these stars which we call "moderate angular momentum loss". In this scenario angular momentum is continuously removed from the stars but at a rate too low to lock the stars with a constant rotation period. We have done a detailed comparison with the recently published rotational period study of NGC 2264 of Makidon et al. (2004). Even though their obtained period distribution of their quality 1 data on NGC 2264 is indistinguishable within the statistical errors from ours, we come to quite different conclusions about the interpretation. One major reason for these discrepanci...

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Section: Spatial Distribution Of Young and Old Starsmentioning

confidence: 76%

Rotational evolution of low mass stars: The case of NGC 2264

Lamm¹,

Mundt²,

Bailer‐Jones³

et al. 2005

A&A

115

218

View full text Add to dashboard Cite

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“…Furthermore, candidates in the Orion OB1 association (log t = 7.00) were investigated. The star numbers given in Tables 3 and 4 are those from Maria (1992;NGC 2232), Walker (1956NGC 2264), Vasilevskis et al (1965;only NGC 2264 #20V), Grubissich & Purgathofer (1962;NGC 2301), Kilambi (1975;NGC 6025) and Koelbloed (1959;NGC 6475). Only one new member of the λ Bootis group in NGC 2264 and three new in the Orion OB1 association (already published in Paper I) were detected (Table 3).…”

Section: Resultsmentioning

confidence: 99%

A spectroscopic survey for λ Bootis stars

Paunzen

Duffee

Heiter

et al. 2001

A&A

109

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Abstract. λ Bootis stars comprise only a small number of all A-type stars and are characterized as nonmagnetic, Population i, late B to early F-type dwarfs which show significant underabundances of metals whereas the light elements (C, N, O and S) are almost normal abundant compared to the Sun. In the second paper on a spectroscopic survey for λ Bootis stars, we present the spectral classifications of all program stars observed. These stars were selected on the basis of their Strömgren uvbyβ colors as λ Bootis candidates. In total, 708 objects in six open clusters, the Orion OB1 association and the Galactic field were classified. In addition, 9 serendipity non-candidates in the vicinity of our program stars as well as 15 Guide Star Catalogue stars were observed resulting in a total of 732 classified stars. The 15 objects from the Guide Star Catalogue are part of a program for the classification of apparent variable stars from the Fine Guidance Sensors of the Hubble Space Telescope. A grid of 105 MK standard as well as "pathological" stars guarantees a precise classification. A comparison of our spectral classification with the extensive work of Abt & Morrell (1995) shows no significant differences. The derived types are 0.23 ± 0.09 (rms error per measurement) subclasses later and 0.30 ± 0.08 luminosity classes more luminous than those of Abt & Morrell (1995) based on a sample of 160 objects in common. The estimated errors of the means are ± 0.1 subclasses. The characteristics of our sample are discussed in respect to the distribution on the sky, apparent visual magnitudes and Strömgren uvbyβ colors.

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“…The Hipparcos catalogue contains at least 4 stars classified by Vasilevskis et al (1965) as highly probable members (see Table 6). In addition, the catalogue contains the brightest star in the field, S Mon, which has a proper motion very similar to the four stars mentioned above.…”

Section: Ngc 2264mentioning

confidence: 99%

Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue

Leeuwen¹

2009

A&A

276

114

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Context. A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming that the accuracies for nearly all stars brighter than magnitude Hp = 8 are improved, by up to a factor 4, compared to the original catalogue. As correlations between the underlying abscissa residuals have also been reduced by more than an order of magnitude to an insignificant level, our ability to determine reliable parallaxes and proper motions for open clusters should be improved. Aims. The new Hipparcos astrometric catalogue is used to derive mean parallax and proper motion estimates for 20 open clusters. The HR-diagrams of the nearest clusters are compared and combined to provide future input to sets of observational isochrones. Methods. Three different methods are applied, according to the proximity of the cluster, to compensate, where needed, for projection effects, spread in position along the line of sight, and the internal velocity dispersion of the cluster stars. Results. The new parallaxes have accuracies between 2 and 2.5 times higher than what had been derived from the original Hipparcos catalogue. At least two to three groups of clusters, mostly of similar ages, are observed to each occupy their own specific space in the HR diagram. A significant discrepancy in distance moduli from those obtained with isochrone-based main-sequence fitting remains, in particular for one of these groups, containing the Pleiades, NGC 2516, and Blanco 1. The difference in absolute magnitudes between this group and one containing the Hyades and Praesepe clusters appears to be correlated with systematic differences in the Strömgren Δc 0 index between those groups. The same dependency has been known to exist for a long time, and is again confirmed by the Hipparcos data, in variations in absolute magnitudes for field stars of the same effective temperature. Conclusions. The positions of the cluster HR diagrams are consistent within different groups of clusters shown for example by the near-perfect alignment of the sequences for the Hyades and Praesepe, for Coma Ber and UMa, and for the Pleiades, NGC 2516, and Blanco 1. The groups are mutually consistent when systematic differences in Δc 0 are taken into account, where the effect of these differences on the absolute magnitudes has been calibrated using field-star observations.

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Membership of the open cluster NGC 2264.

Cited by 48 publications

References 0 publications

Rotational evolution of low mass stars: The case of NGC 2264

Rotational evolution of low mass stars: The case of NGC 2264

A spectroscopic survey for λ Bootis stars

Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue

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