Near-IR speckle imaging of massive young stellar objects
We present near-IR speckle images of 21 massive Young Stellar Objects(YSOs) associated with outflows. The aim of this study is to search forsub-arcsecond reflection nebulae associated with the outflow cavity. Wefind that 6 of the massive YSOs show a conical nebula which can beinterpreted in terms of reflected light from the dusty walls of theoutflow cavity. In all cases, the small scale structures seen in ourimages are compared with outflow indicators found in the literature. Noclear correlation is found between the presence of the reflectionnebulosity and any property such as degree of embeddedness. We also notethat 3 of the sources show close companions, one of them belonging alsoto the sample with conical nebula.Figures \ref{S140SpeckleFig}, \ref{S255SpeckleFig},\ref{Ha101Fig}-\ref{HGL490Fig} and\ref{GL2591SpeckleFig}-\ref{GL5180peckleFig} are only available inelectronic form at http://www.edpsciences.org
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The Pre-Main-Sequence Stars and Initial Mass Function of NGC 2264
UBVRI and Hα CCD photometry has been performed in the southernregion of NGC 2264 around the Cone Nebula. A nearly complete list ofpre-main-sequence (PMS) members in the cluster has been made from thecompilation of Hα emission stars identified in this study plusthose selected in previous investigations, together with stars withX-ray emission. Using the H-R diagram, we tested a set of four PMSevolution models based on the PMS age and age spread estimate for thecluster and the mass-age relationship among individual stars. Theresultant initial mass function (IMF) is in good agreement with thefield star IMF of the solar neighborhood, with an IMF slope Γ=-1.7in the mass range 0.3<=logm<=0.8.
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ASCA Observations of the NGC 2264 Molecular Cloud
We have made ASCA observations of the molecular cloud associated withNGC 2264, and detected nine and five sources in the soft and hard X-rayband images, respectively. Most of them are identified with knownpre-main-sequence stars or protostellar objects. Two Class I sourceswith intermediate luminosities and one Class II source associated withmolecular outflow are promising candidates for X-ray emitters. Anoptically thin hot-plasma model with two components can reproduce theGIS X-ray spectra, including both of the Class I sources. The hardX-rays probably arise from these Class I sources, and are intrinsicallyvery luminous, >1032 erg s-1 in the 0.7-10.0keV energy band, and their luminosities lie between low-mass Class Isources and that of the W 3 massive core region. Since near-infraredsurvey data reveal that Class I sources are surrounded by embedded youngclusters, the soft X-ray components could be explained by aggregates oflow-mass pre-main-sequence stars.
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Spectral classification of O-M stars on the basis of UBV photometry
A new technique allowing the Q-method to be used surely for both thespectral classification of young O-A0 stars and older spectralsubclasses A1-M5 is described. Characteristics of interstellar lightabsorption dependence on distance in the given direction of the sky isused as a main criterion for excluding possible multiplicity of starspectral estimates at some constant values of QUBV.Information on open cluster membership probabilities is also useful asadditional criterion of the spectral classification. The method wastested on stars up to V=14 mag in directions of young open clusters NGC2244 and NGC 2264. The spectral study based on UBV photometry wasextended to faint stars of NGC 2264 in the V magnitude range 17-22 mag.
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BVRI photometry of the star-forming region NGC 2264: the initial mass function and star-forming rate
The pre-main sequence (PMS) population in the mass range between ~ 0.2and ~ 3 M_sun in southern part of the star-forming region NGC 2264 hasbeen studied, determining both the Initial Mass Function in the regionas well as the star-formation rates for different mass ranges. Thesample is a composite one, derived through the union of samples obtainedthrough different techniques and each suffering from different biases:previously known PMS stars in the region from the literature,photometrically-selected T Tauri candidates (from our own photometricdata, discussed in detail in the present paper) and X-ray selected PMScandidates (discussed in detail in a companion paper) have been joinedto form a sample which we show to be statistically complete (i.e. freefrom the biases which affect each of the parent samples) down to =~ 0.6M_sun (while being incomplete at lower masses). Individual masses andages have been derived by placing the individual stars on evolutionarytracks, allowing us to derive both the IMF and the star formation rate.The Initial Mass Function thus derived for NGC 2264 shows evidence for abimodal distribution of masses, with a break in the IMF at around 1M_sun. Based on observations with the VATT: the Alice P. LennonTelescope and the Thomas J. Bannan Astrophysics Facility. Table~3 isavailable in electronic form at CDS via ftp 130.79.128.5
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Uvby-Beta and JHKLM Photometry of Peculiar Stars in the Galactic Cluster NGC2264
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102..201N&db_key=AST
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VBLUW photometry of the very young open cluster NGC 2264
This study presents and discusses VBLUW photometry of 112 stars with Vless than 13 in the area of the very young cluster NGC 2264.Temperatures, gravities, and reddening for stars hotter than 8400 K aredetermined. The reddening and the distance are found to be in goodagreement with the results of other references; to the existing list ofpresumable nonmembers, six stars are tentatively added as possiblenonmembers.
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Radial velocities of stars in open clusters
A CORAVEL type spectrometer was used to measure precise radialvelocities of 116 late-type stars of spectral classes F5 - M5 in thefields of 18 open clusters. Probable cluster members were selected onthe basis of kinematic and photometric data. New or improved radialvelocities for 12 open clusters were thus obtained.
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Remarks to Lapicz positions of stars in NGC 2264.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990RMxAA..20..113L&db_key=AST
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Membership and photometric abundances of red evolved stars in open clusters
UBV and DDO photometric observations of 31 red evolved stars toward 11open clusters, obtained with the 41-cm and 91-cm telescopes at CerroTololo Interamerican Observatory on four nights in 1978, are reported.The data are compiled in tables and characterized for each cluster, andtwo criteria are used to determine the probability that a star is amember of a cluster. Six of the clusters are found to contain oneevolved red star, one has two, one has four, and three have none; theother 19 stars are seen as red field objects. The estimated cluster Fe/Habundance ratios range from -0.2 to +0.3, and the red giants in theclusters NGC 2335 and NGC 2567 are found to have CN strengths like thoseseen in Hyades giants. The unusual weakness of the 421.6-nm band of CNfor star 108 in NGC 2548 is attributed either to unusual composition andproper motion or to its nonmembership in the cluster despite meeting thephotometric criteria.
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Positions of stars in NGC 2264
Positions in the region of NGC 2264, obtained using the Lick CarnegieAstrograph are presented. The methods used to obtain the positions arebriefly discussed.
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New UBVRI photometry for 900 supergiants
A description is presented of the results obtained in connection with asystematic program of supergiant photometry on the Johnson UBVRI system.During the eight years after the start of the program, almost 1000 starshave been observed, about 400 three or more times each. The originalselection of stars used the spectral type catalog of Jaschek et al.(1964) to choose supergiants. Since observations were possible from bothChile and Canada, no declination limits were imposed, and no particularselection criteria were imposed other than to eliminate carbon stars.These are so red as to require enormous extrapolations of thetransformation equations.
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High-luminosity red stars in or near galactic clusters. Paper I
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..960E&db_key=AST
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Photographic photometry in the field of NGC 2264.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..379K&db_key=AST
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Catalogue des étoiles mesurées dans le système photométrique de l'Observatoire de Genève
Not Available
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Membership of the open cluster NGC 2264.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965AJ.....70..797V&db_key=AST
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Some Radial-Velocity Observations of K-Type Stars in NGC 2264
Not Available
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Studies of Extremely Young CLUSTERS.I.NGC 2264.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956ApJS....2..365W&db_key=AST
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