The T Tauri Star Population of the Young Cluster NGC 2264
An Hα emission survey of the young cluster NGC 2264 in the Mon OB1association resulted in the detection of 490 Hα emission stars ina 25'×40' field approximately centeredbetween the O7 V multiple star S Mon and the Cone Nebula. The survey wascarried out with the wide-field grism spectrograph (WFGS) on theUniversity of Hawaii 2.2 m telescope on Mauna Kea. X-ray observationsmade with the European Photon Imaging Camera on board the European SpaceAgency's XMM-Newton satellite observatory will be discussed in asubsequent paper. Optical (BVRCIC) photometry wasobtained for selected fields to supplement similar data from theliterature. Spectra covering the 6000-8000 Å region at aresolution of R~3000 (adequate for the determination of Li Iλ6708 line strengths) were obtained for 150 Hα and X-rayemission sources with the Gemini Multi-Object Spectrograph.Near-infrared spectra (1-2.5 μm) of a number of T Tauri stars (TTSs),X-ray sources, and LHα25 (W90) were also obtained using SpeX onthe Infrared Telescope Facility. Ages and masses for the Hαemitters were inferred from the isochrones and evolutionary tracks ofD'Antona & Mazzitelli. The median age for the TTS population isabout 1.1 Myr, but a considerable dispersion, from 0.1 to 5 Myr, existsfor individual objects. Several fields in the cluster were observed withthe WFGS on more than one occasion, permitting an examination ofHα variability over long baselines in time. About 90% of theclassical T Tauri stars (CTTSs) showed changes in W(Hα) of atleast 10%, while 57% varied at levels of 50% or more. No evidence wasfound for a significant pool of dormant Hα emitters. Summing themasses of the TTSs and the OB stellar population of NGC 2264, a lowerlimit for the total stellar mass content of the cluster is about 430Msolar. This is less than 1% of the total mass of the atomicand molecular gas believed to be associated with NGC 2264. Evidence forhierarchical structure within the cluster is suggested by the spatialdistribution of TTSs. Four concentrations of Hα emitters areevident: two near S Mon and two near the Cone Nebula. The median age ofthe TTSs in the immediate vicinity of S Mon was found to be greater thanthat of the TTSs near Allen's infrared source (IRS-1), but a significantdispersion is present. From the rotational data of Lamm et al. andMakidon et al., 241 of the TTSs are periodic variables, 150 weak-line TTauri stars (WTTSs) and 91 CTTSs, while 123 stars are irregularvariables (30 WTTSs and 93 CTTSs). A weak-to-moderate positivecorrelation is found between H-K color and Prot for theCTTSs, in the sense that stars having longer periods tend to have largerH-K colors. A similar positive correlation is found betweenLHα and Prot among the CTTSs. Nostatistically significant correlation is found between Protand theoretical age or between Prot and LX. Othertopics discussed include the fraction of Hα emitters that areWTTSs, f(WTTS)=N(WTTS)/N(TTS), for clusters of different ages; therelative detectability of Hα emission using WFGS and narrowbandfilter imaging techniques; and the correlation of W(Li I) withTe, age, H-K color, and W(Hα).
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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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UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
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Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
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An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
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Uvby-beta observations of 528 type B stars with V between the 8th and 9th magnitude
The paper presents uvby-beta measurements of 528 type B stars selectedfrom the SAO Catalog on the basis of two criteria: the spectral types inthe range B3-B5 and mV between the 8th and the 9th magnitude. Reddeningindependent (c1) values are estimated from the spectral classificationand compared to the observed values. No systematic trend with observed(b-y), H-beta, or spectral type appears to be present, but the range of(c1) residuals is surprisingly large. A rather large part of the starshas small beta values, smaller than for the BIa supergiants. Only twoare classified as O stars and most of them have the suffix e, ne, ornne. Most beta values for the O type stars are slightly above the upperlimit of 2.585 m.
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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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Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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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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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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Walker No. 67 in NGC 2264 - A candidate for strong interstellar circular polarization
Not Available
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The value of R in Monoceros
Recent photometric and spectroscopic observations are used inconjunction with other data for early-type stars in northern Monocerosin order to investigate the local value of R (the ratio of total toselective extinction). From a variable-extinction analysis, it isconcluded that a ratio of approximately 3.2 is appropriate for thegeneral interstellar extinction in this region and that there is noevidence here for the existence of local anomalies. The two majorassociations Mon OB 1 and Mon OB 2 are clearly delineated and are foundto exhibit properties typical of such young stellar groups. Derivedproperties for a few interesting stars are presented.
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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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Photoelectric measures of Hydrogen-line absorption in early-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962MNRAS.123..521B&db_key=AST
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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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