A rotational and variability study of a large sample of PMS stars in NGC 2264
We present the results of an extensive search for periodic and irregularvariable pre-main sequence (PMS) stars in the young (2-4 Myr) opencluster NGC 2264, based on photometric monitoringusing the Wide Field Imager (WFI) on the 2.2 m telescope on La Silla(Chile). In total, about 10 600 stars with IC magnitudesbetween 9.8 mag and 21 mag have been monitored in our 34 arcmin ×33 arcmin field. Time series data were obtained in the ICband in 44 nights between Dec. 2000 and March 2001; altogether weobtained 88 data points per star. Using two different time seriesanalysis techniques (Scargle periodogram and CLEAN) we found 543periodic variable stars with periods between 0.2 days and 15 days. Also,484 irregular variable stars were identified using aχ2-test. In addition we have carried out nearlysimultaneous observations in V, RC and a narrow-band Hαfilter. The photometric data enable us to reject background andforeground stars from our sample of variable stars according to theirlocation in the IC vs. (RC-IC)colour-magnitude and (RC-Hα) vs.(RC-IC) colour-colour diagrams. We identified 405periodic variable and 184 irregular variable PMS stars as clustermembers using these two different tests. In addition 35 PMS stars forwhich no significant variability were detected could be identified asmembers using an Hα emission index criterion. This yields a totalof 624 PMS stars in NGC 2264, of which only 182 were previously known.Most of the newly found PMS stars are fainter than IC ≃15 mag and of late spectral type (M 2). We find that the periodicvariables, as a group, have a smaller degree of variability and smallerHα index than the irregular variables. This suggests that thesample of periodic variables is biased towards weak-line T Tauri stars(WTTSs) while most of the irregular variables are probably classical TTauri stars (CTTSs). We have quantified this bias and estimated that theexpected fraction of WTTSs among PMS stars in the cluster is 77%. Thisis relatively close to the fraction of WTTSs among the periodicvariables which is 85%. We also estimated the total fraction ofvariables in the cluster using only two well selected concentrations ofPMS stars called NGC 2264 N & S in which we can easily estimate thetotal number of PMS stars. We find that at least 74% of the PMS stars inthe cluster with IC≤ 18.0 mag were found to be variable(either periodic or irregular) by our study. This number shows that oursearch for PMS stars in NGC 2264 through extensive and accuratephotometric monitoring is very efficient in detecting most PMS starsdown to at least IC=18.0 mag.Full Tables 4 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/417/557
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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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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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Measurements of double stars 1993.67 - 1998.13
624 Micrometer Measurements of 224 pairs with a 32.5 cm Cassegrain, 719Measurements of 310 double stars with a 360 mm Newtonian are given.Tables 1 to 4 are available in electronic form only at the CDS130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html
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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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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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Equatorial coordinates of double and multiple star components measured on GPO astrographic plates
Equatorial coordinates are given for some of the multiple starcomponents having incomplete or inconsistent information in the IndexCatalog of Visual Double Stars. Two photographic plates were taken foreach system with incomplete or inconsistent information using the GPOastrograph. The plate measurement and reduction techniques used aredescribed.
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Catalog of BV magnitudes and spectral classes of 6000 stars
The present catalog, compiled at the Abastumani Observatory, contains BVmagnitudes and spectral classes of about 6000 stars up to V(lim) = 13.0min five circular areas of 18 sq deg located near the salactic-equatorplane. The catalog is intended for star-statistics studies ofstar-formation regions.
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Ultraviolet and X-ray observations of NGC 2264
An IUE satellite search is reported for chromospheric emission in the UVspectra of the brightest pre-main sequence stars the open cluster NGC2264. Einstein X-ray observations to search for variability of thebright O7 V ((f)) star S Mon = W131, which may be the most massivemember of the cluster, are also reported. Fifteen cluster members ofspectral type B-K, ranging in age from a million to ten million yr, wereobserved in the ultraviolet. The only star exhibiting chromosphericemission is W79, a faint, heavily veiled T Tauri star that lies belowthe main sequence of NGC 2264. The observations are consistent with thegenerally accepted idea that chromospheric activity of late-type starssubsides with age.
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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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Study of the open cluster NGC 2264
Photoelectric UBV magnitudes and colors have been determined for 138stars in NGC 2264, having a membership probability greater than 50percent on the basis of proper motion studies. The reddening across thecluster is variable. The distance modulus to the cluster is estimated at9.5 + or - 0.2 mag.
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Circumstellar shells in NGC 2264 : a reevaluation.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJ...213..427W&db_key=AST
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Premain sequence masses and the age spread in the ORI cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81..845M&db_key=AST
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Pre-main sequence masses and evolution in NGC 2264.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87...97M&db_key=AST
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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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Infra-red observations of young stars. I. Stars in young clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.161...85C&db_key=AST
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The distribution of stars and obscuring matter in a Monoceros field
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....7...35K&db_key=AST
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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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Recherches sur les Proprietes des Etoiles Doubles ou Multiples Largement Separees EN Relation avec les Problemes d'Evolution
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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