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A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| Is the Emerging Massive Cluster NGC 2244 a Twin Cluster?
We present in this paper the first near-infrared study of the young opencluster NGC 2244, which is well known for its partially embedded naturein the Rosette Nebula. Based on the spatially complete Two Micron AllSky Survey, the young OB cluster indicates apparent substructures. It issurprisingly resolved into a compact core that matches well thecongregation of massive OB stars in the optical, a satellite cluster ata distance of 6.6 pc west of the center of NGC 2244 and probably a majorstellar aggregate resembling an arc in structure right below the core.This infrared study provides various new updates on the nature of theyoung open cluster, including its central position, physical scale, andstellar population. A disk fraction of ~20.5%+/-2.8% is achieved for itsmembers with masses above 0.8 Msolar. NGC 2244 is thus aunique example for the study of embedded clusters.
| Abundances from disentangled component spectra: the eclipsing binary V578 Mon
Chemical abundances of the early-B type components of the binary V578Mon are derived from disentangled component spectra. This is a pilotstudy showing that, even with moderately high line-broadening, metalabundances can be derived from disentangled spectra with a precision of0.1 dex, differential to sharp-lined single stars of the same spectraltype. This binary is well-suited to such an assessment because of itsyouth as a member of the Rosette Nebula cluster NGC 2244, strengtheningthe expectation of an unevolved ZAMS chemical composition. The method isuseful for studying rotationally driven mixing in main-sequence stars,since fundamental stellar parameters are known with higher accuracy in(eclipsing) binaries. This paper also evaluates of the bias that mightbe present in disentangled spectra.
| Close binary stars in ob-association regions i. preliminary investigation
We performed a sample of O- and B-eclipsing binary stars inOB-association regions and obtained the preliminary list of 147 binariesin 45 OB-association regions. We tried to elucidate the question whether(or not) the close binaries belong to corresponding OB-associations,from the commonness of their proper motions, radial velocities anddistances. Based on the completeness of the data,the binaries aredevided into three groups and the scheme for calculation of degree ofbelonging of stars to OB-associations is developed. Necessary data arenot available for nine systems and they are given in a specific table.For 12 cases, the binaries project onto the regions of two associations.We show that 33 (22.3%) close binary stars are members, 65 (43.9%) areprobable members and 39 (26.4%) are less probable members of theOB-associations. We find that 11 binaries belong to the Galaxybackground. The comparison of the distributions of orbital periods forthe binaries in OB-associations and for O-, B-binaries of the Galaxybackground shows their considerable differences in the vicinity of thetwo-day period.
| 10 MK Gas in M17 and the Rosette Nebula: X-Ray Flows in Galactic H II Regions
We present the first high spatial resolution X-ray images of twohigh-mass star forming regions, the Omega Nebula (M17) and the RosetteNebula (NGC 2237-2246), obtained with the Chandra X-Ray ObservatoryAdvanced CCD Imaging Spectrometer instrument. The massive clusterspowering these H II regions are resolved at the arcsecond level intomore than 900 (M17) and 300 (Rosette) stellar sources similar to thoseseen in closer young stellar clusters. However, we also detect softdiffuse X-ray emission on parsec scales that is spatially and spectrallydistinct from the point-source population. The diffuse emission hasluminosity LX~=3.4×1033 ergs s-1in M17 with plasma energy components at kT~=0.13 and ~=0.6 keV (1.5 and7 MK), while in Rosette it has LX~=6×1032ergs s-1 with plasma energy components at kT~=0.06 and ~=0.8keV (0.7 and 9 MK). This extended emission most likely arises from thefast O star winds thermalized either by wind-wind collisions or by atermination shock against the surrounding media. We establish that onlya small portion of the wind energy and mass appears in the observeddiffuse X-ray plasma; in these blister H II regions, we suspect thatmost of it flows without cooling into the low-density interstellarmedium. These data provide compelling observational evidence that strongwind shocks are present in H II regions.
| A Method for Simultaneous Determination of AV and R and Applications
A method for the simultaneous determination of the interstellarextinction (AV) and of the ratio of total to selectiveextinction (R), derived from the 1989 Cardelli, Clayton, & Mathisfitting of the interstellar extinction law, is presented and applied toa set of 1900 color excesses derived from observations of stars inUBVRIJHKL. The method is used to study the stability of AVand R within selected regions in Perseus, Scorpius, Monoceros, Orion,Sagittarius, Ophiuchus, Carina, and Serpens. Analysis shows that R isapproximately constant and peculiar to each sector, with mean valuesthat vary from 3.2 in Perseus to 5.6 in Ophiuchus. These results aresimilar to published values by Aiello et al., He et al., Vrba &Rydgren, O'Donnell, and Cardelli, Clayton, & Mathis.
| The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
| UBVI and Hα Photometry of the Young Open Cluster NGC 2244
New UBVI and Hα photometry has been performed for the young opencluster NGC 2244. We classified 30 OB stars as being members of thecluster using proper-motion data and spectral types from previousinvestigators, along with photometric diagrams obtained in this study.We measured Hα emission strength of the stars by Hαphotometry and set up a selection criterion to select pre-main-sequence(PMS) stars with Hα emission. Fourteen PMS stars and seven PMScandidates were found using the criterion. In addition, six stars foundnear the positions of ROSAT HRI X-ray sources were assumed to be PMSstars and the optical counterparts of these X-ray sources. We determineda reddening of =0.47+/-0.04 for the cluster and atotal-to-selective extinction ratio of RV=3.1+/-0.2. Thedistance modulus derived was V0-MV=11.1. Bycomparing our photometric results with theoretical evolution models, wederived a main-sequence turnoff age of 1.9 Myr and a PMS age spread ofabout 6 Myr. The slope of the initial mass function, Γ, calculatedin the mass range 0.5<=logm<=2.0 could be flat(Γ=-0.7+/-0.1).
| Optical properties of X-ray selected stars in NGC 2244 in the Rosette Nebula
We present high spatial resolution optical photometry of NGC 2244 in theRosette Nebula using the NOAO MOSAIC Imager at Kitt Peak. We obtainedBVIR and Hα images of the central cluster and surrounding nebulae,and present results for 138 sources selected from X-ray observationswith the ROSAT PSPC and HRI. Color-magnitude diagrams of the clustershow a large number of the stars are still undergoing contraction ontothe main sequence. The faintest X-ray selected cluster members have thehighest X-ray-to-optical luminosities (Lx sog7*E30 erg s-1; Lx/Lbol ~10-2 to 10-3) and indicate they are a populationof young active late-type stars. Hα emission from the X-rayemitters is also remarkable. We have extended the detections of PMSstars in NGC 2244 well into the range of K spectral types. While most ofthe cluster stars are located in the color-magnitude diagrams in betweenthe ZAMS and the 3 Myrs isochrone, significantly younger low mass starsexist and confirm earlier reports that star formation is still going onin the Rosette Nebula/NGC 2244 region. Table 3 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/384/890
| Chemical Composition of V578 Mon - An Eclipsing Binary in the Rosette Nebula Cluster NGC 2244
The fortunate circumstance that the double-lined eclipsing binary V578Mon is member of the young open cluster NGC 2244, situated in thecentral hole of the Rosette Nebula, allows to derive the physicalproperties and evolutionary status of its components as well as the ageof and the distance to the cluster and the nebula. A new approach, usingFourier disentangling to separate the composite binary spectra intoindividual component spectra (c.f. Hensberge, Pavlovski &Verschueren 2000, A&A 358, 553) leads to high precision results. Thedisentangled spectra can thereafter be analyzed as if it were singlestar spectra. The present contribution is the continuation of our workon V578 Mon and concentrates on the derivation of preliminary abundancesfor both components. The rotational velocities are about 100 and 120 kms-1; hence, abundances are derived differentially to thetemplate spectrum of the sharp-lined cluster star NGC2244-#201.Abundances for #201 and another two B1 stars were previously derived(Vrancken et al. 1997, A&A 320, 878). Now, we have chemicalabundances for five early-B stars in the range of the effectivetemperatures from 26 000 - 30 000 K. These stars have projectedrotational velocties ranging from 22 to 260 km s-1. All thesestars have the same atmospheric chemical composition in He and CNOelements within an rms accuracy of about 0.05 dex.
| On the eclipsing nature of CPD-59degr2628
The spectroscopic binary CPD -59°2628 (Sp = O9.5V) has been discovered to be a detached eclipsing binary, and we presentan analysis based on new light curves, published spectroscopy and twonew high-resolution spectra. uvby light curves from more than 2000observations are analysed with the WINK and the Wilson-Devinney (WD)programs. Geometric distortions and photometric effects from theproximity of the components are included in the computations. Thedetached system has a close circular orbit of high inclination and highmaximum projected velocities. We find a photometric period P=1fd47 whichis consistent with the spectroscopy-binary period by Solivella &Niemela (\cite{solivella&niemela99}). We use this period to rematchthe misidentified radial velocities from Levato et al.(\cite{levato&al91}) and apply them in an analysis using the methodof Lehmann-Filhes. We find that CPD -59°2628 is ayoung system close to the ZAMS. Its distance is 2.6+/-0.1 kpc and it hasa systemic velocity of -19 km s-1, confirming its membershipin the cluster Trumpler 16 (radial velocity -23.5 kms-1). The temperatures are 32 000 K for the hotter star (A)and 30 000 K for the cooler (B). We determine the absolute dimensions(solar units): M_A=14.0+/-2.0, R_A=5.29+/-0.26, M_B=11.7+/-1.8 andR_B=4.38+/-0.22. By adopting E(b-y)=0.306, we get M_{bol,A}=-6.3+/-0.1,MV,A=-3.2+/-0.1, M_{bol,B}=-5.6+/-0.1 andMV,B=-2.7+/-0.1. Theoretical stellar models from Claret(\cite{claret95}), including convective-core overshooting and mass lossfor a composition (X=0.70, Z=0.02), appear to fit the components at anage of ~ 2 Myr. Based on observations obtained at the European SouthernObservatory at La Silla, Chile (Applications 62H-0110, 62H-0110 and64.L-0031) and the South African Astronomical Observatory, Sutherland,South Africa.
| 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.
| The eclipsing binary V578 Mon in the Rosette nebula: age and distance to NGC 2244 using Fourier disentangled component spectra
V578 Mon is a member of the young stellar cluster NGC 2244 which isembedded in the Rosette nebula. It is a double-lined binary, consistingof two early-B type components which eclipse each other partially duringtheir 2.40848-day orbit. A novel technique of Fourier disentangling isapplied to disentangle the spectrum of the binary into the spectra ofits components, allowing a direct spectroscopic temperaturedetermination for each component. Together with an analysis of the lightcurve, the spectral disentangling process allows us to derive theorbital and fundamental stellar parameters. The hotter star (T_eff = 30000 K) has a mass of 14.5 Msun and a radius of 5.2 Rsun. The cooler one (T_eff = 26 400 K) has a mass of 10.3 Msun and a radius of 4.3 Rsun . Both stars are well insidetheir critical Roche lobe and move in an eccentric orbit (e=0.087) whichhas a semi-major axis of 22 Rsun and is seen at aninclination of 72.6degr . The rotation of both stars is synchronizedwith the orbital motion. The systemic velocity of 34.9 km s-1,confirms that the binary belongs to NGC 2244. The age of the binary,and hence of NGC 2244, is (2.3±0.2) 106 years. Fromthe fundamental stellar parameters and the interstellar absorption, thedistance to the cluster is derived to be 1.39 ±0.1 kpc, i.e.slightly lower than that found from photometric studies. Its age andspace velocity indicate that NGC 2244 is formed in the galactic plane.The high accuracy obtained (e.g. probable errors of 0.5% for the masses,1m -1.5% for the radii, despite the lack of total eclipses,and 1.5% for the temperatures) is a direct consequence of the spectraldisentangling technique, which as a by-product delivers very accurateradial velocities for all orbital phases. Based on observations obtainedat the European Southern Observatory (ESO), La Silla, Chile Table 5 isonly available in electronic form at the CDS via anonymous ftp to130.79.128.5 or at http://cdsweb.u-strasbg.fr
| Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
| 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.
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| New Perspectives on AX Monocerotis
AX Moncerotis is a 232d, noneclipsing, interacting binary star thatconsists of a K giant, a Be-like giant, and large amounts ofcircumstellar material. The K star is almost certainly a synchronousrotator and is probably in contact with its critical lobe. The Be starwas believed to be a rapid rotator based on extremely wide absorptionlines, but new spectra show that these lines arise from thecircumstellar environment. Hydrogen emission, also circumstellar, ismany times stronger than the continuum. Near-ultraviolet light curvesexhibit a 0.5 mag dip near phase 0.75, but there is no such variabilityat longer wavelengths. Gas flow trajectories from the cusp of the K startoward the Be star provide a simple explanation for the photometric andspectroscopic behavior. We may have found a decreasing orbital period,but more data are necessary to confirm this result. We present severalmodels for AX Mon based on (1) new and archival visible photometry, (2)archival ultraviolet spectroscopy, (3) new and archival visiblespectroscopy, (4) new visible polarimetry, and (5) new radio photometry.Future observations, including optical interferometry, are proposed.
| The Initial Mass Function and Massive Star Evolution in the OB Associations of the Northern Milky Way
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...454..151M&db_key=AST
| 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.
| Predicting the Secondary Minima Depths and Spectra of the Main Components for the Dm-Type Eclipsing Variable Stars
Not Available
| More radial-velocity measurements in young open clusters
Further high resolution radial-velocity measurements are reported in 23young open clusters using the Kitt Peak CCD coude spectrograph on the0.9-m feed telescope. The radial velocities for the cluster stars arederived with the technique of cross correlation. The internal precisionof the velocity measurements is typically 2 km/s for early type stars.From these new data and previously published velocities, the observedstars in two clusters, NGC 663 and NGC 2287, were found to show arelatively small dispersion in the measured mean velocities. Furtherobservations of stars in young clusters will be useful in helping toestablish an early-type-star-velocity standard system.
| IRAS observations of the Rosette nebula complex
A detailed study of the infrared radiation associated with the Rosettenebula complex has been conducted using the IRAS data. The results ofthe study suggest that most of the infrared sources detected by IRASwhich are embedded in the Rosette molecular cloud are associated withdense molecular clumps. The luminosities of these sources cover therange 100-12,000 solar luminosities, corresponding to B1-B4 stellartypes.
| UVBY beta photometry of stars in the field of NGC 2244 and NGC 2264
Results are presented from uvby beta photometric observations of 34stars in the fields of NGC 2244 and NGC 2264. Photometric andastrometric indicators suggest that about a third of the sample arenonmembers of the clusters. Cluster color excesses are determined forthe two clusters. For the stars examined, log g and effectivetemperature are estimated. Also, stellar radii, masses, and positions inthe H-R diagram are calculated. The cluster ages and the main-sequencelifetime for massive stars show that star formation in the region hasnot been restricted to a single epoch.
| On the distances to the young open clusters NGC 2244 and NGC 2264
A new determination of the distances of the young open clusters NGC 2244and NGC 2264 is presented. It is based on distance moduli for individualOB-type stars in which the influence of the anomalous ratio of total toselective extinction, if any, is taken into account. A discussion isincluded, first, of the accuracy of the color-difference method comparedto that of other current methods for determining R and, second, of theerrors in the determination of the distances for clusters embedded innonuniform H II regions. New photoelectric measurements (UBVRI andJHKLM), and new spectrophotometric data (IDS spectra) are presented forOB-type stars in these clusters as well as summaries of publishedphotometric data. The locations in the H-R diagram of the program starsseem to suggest that these massive stars are on the main sequence,supporting the idea of continuous star formation.
| Small Magellanic Cloud: H-gamma-line equivalent widths and luminosity classes of the brightest blue star members
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&AS...69..421A&db_key=AST
| 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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Observation and Astrometry data
| Constellation: | Monoceros |
| Right ascension: | 06h32m00.61s |
| Declination: | +04°52'40.9" |
| Apparent magnitude: | 8.579 |
| Proper motion RA: | -0.6 |
| Proper motion Dec: | 0.4 |
| B-T magnitude: | 8.715 |
| V-T magnitude: | 8.591 |
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