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Random forest automated supervised classification of Hipparcos periodic variable stars
We present an evaluation of the performance of an automatedclassification of the Hipparcos periodic variable stars into 26 types.The sub-sample with the most reliable variability types available in theliterature is used to train supervised algorithms to characterize thetype dependencies on a number of attributes. The most useful attributesevaluated with the random forest methodology include, in decreasingorder of importance, the period, the amplitude, the V-I colour index,the absolute magnitude, the residual around the folded light-curvemodel, the magnitude distribution skewness and the amplitude of thesecond harmonic of the Fourier series model relative to that of thefundamental frequency. Random forests and a multi-stage scheme involvingBayesian network and Gaussian mixture methods lead to statisticallyequivalent results. In standard 10-fold cross-validation (CV)experiments, the rate of correct classification is between 90 and 100per cent, depending on the variability type. The main mis-classificationcases, up to a rate of about 10 per cent, arise due to confusion betweenSPB and ACV blue variables and between eclipsing binaries, ellipsoidalvariables and other variability types. Our training set and thepredicted types for the other Hipparcos periodic stars are availableonline.
| A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun
Traditionally, runaway stars are O- and B-type stars with large peculiarvelocities. We would like to extend this definition to young stars (upto ?50 Myr) of any spectral type and to identify those present in theHipparcos catalogue by applying different selection criteria, such aspeculiar space velocities or peculiar one-dimensional velocities.Runaway stars are important for studying the evolution of multiple starsystems or star clusters, as well as for identifying the origins ofneutron stars. We compile the distances, proper motions, spectral types,luminosity classes, V magnitudes and B-V colours, and we utilizeevolutionary models from different authors to obtain star ages. We studya sample of 7663 young Hipparcos stars within 3 kpc from the Sun. Theradial velocities are obtained from the literature. We investigate thedistributions of the peculiar spatial velocity and the peculiar radialvelocity as well as the peculiar tangential velocity and itsone-dimensional components and we obtain runaway star probabilities foreach star in the sample. In addition, we look for stars that aresituated outside any OB association or OB cluster and the Galactic planeas well as stars for which the velocity vector points away from themedian velocity vector of neighbouring stars or the surrounding local OBassociation/cluster (although the absolute velocity might be small). Wefind a total of 2547 runaway star candidates (with a contamination ofnormal Population I stars of 20 per cent at most). Thus, aftersubtracting these 20 per cent, the runaway frequency among young starsis about 27 per cent. We compile a catalogue of runaway stars, which isavailable via VizieR.
| Masses and luminosities of O- and B-type stars and red supergiants
Massive stars are of interest as progenitors of supernovae, i.e.neutron stars and black holes, which can be sources of gravitationalwaves. Recent population synthesis models can predict neutron star andgravitational wave observations but deal with a fixed supernova rate oran assumed initial mass function for the population of massive stars. Here we investigate those massive stars, which are supernovaprogenitors, i.e. with O- and early B-type stars, and also allsupergiants within 3 kpc. We restrict our sample to those massive starsdetected both in 2MASS and observed by Hipparcos, i.e. only those starswith parallax and precise photometry. To determine the luminositieswe calculated the extinctions from published multi-colour photometry,spectral types, luminosity class, all corrected for multiplicity andrecently revised Hipparcos distances. We use luminosities andtemperatures to estimate the masses and ages of these stars usingdifferent models from different authors. Having estimated theluminosities of all our stars within 3 kpc, in particular for all O- andearly B-type stars, we have determined the median and mean luminositiesfor all spectral types for luminosity classes I, III, and V. Ourluminosity values for supergiants deviate from earlier results: Previouswork generally overestimates distances and luminosities compared to ourdata, this is likely due to Hipparcos parallaxes (generally moreaccurate and larger than previous ground-based data) and the fact thatmany massive stars have recently been resolved into multiples of lowermasses and luminosities. From luminosities and effective temperatureswe derived masses and ages using mass tracks and isochrones fromdifferent authors. From masses and ages we estimated lifetimes andderived a lower limit for the supernova rate of ?20 events/Myraveraged over the next 10 Myr within 600 pc from the sun. These data arethen used to search for areas in the sky with higher likelihood for asupernova or gravitational wave event (like OB associations).
| Rotational Velocities of the Components of 23 Binaries
By using high dispersion spectra obtained by the 1.8 m telescope ofBohyunsan Optical Astronomy Observatory (South Korea), multilineleast-square deconvolution of line profiles, and Fourier analysistechniques, we obtained the rotational velocities of the components of23 binary systems. The rotational velocities for nine primary, eightsecondary, and one tertiary components of these systems were determinedfor the first time. The rotational velocities for primary components ofseven systems appeared to be significantly different than thecorresponding synchronous values (more than twice as fast for fivesystems, and less than half as fast for two systems). Our velocities forAU Mon, RY Gem, and RZ Eri are significantly lower than the previouslypublished values obtained by using one or very few lines. We show thatthese discrepancies can be explained by strong blending of the lines inthe spectra of the primaries with strong lines of the secondaries, byinfluence of gaseous streams, and maybe by nonsolar chemicalcompositions.
| LBT Discovery of a Yellow Supergiant Eclipsing Binary in the Dwarf Galaxy Holmberg IX
In a variability survey of M81 using the Large Binocular Telescope wehave discovered a peculiar eclipsing binary (MV~-7.1) in thefield of the dwarf galaxy Holmberg IX. It has a period of 271 days, andthe light curve is well fit by an overcontact model in which both starsare overflowing their Roche lobes. It is composed of two yellowsupergiants (V-I~=1 mag, Teff~=4800 K), rather than the farmore common red or blue supergiants. Such systems must be rare. While wefailed to find any similar systems in the literature, we did, however,note a second example. The SMC F0 supergiant R47 is a bright(MV~-7.5) periodic variable whose All Sky Automated Survey(ASAS) light curve is well fit as a contact binary with a 181 dayperiod. We propose that these systems are the progenitors of supernovaelike SN 2004et and SN 2006ov, which appeared to have yellow progenitors.The binary interactions (mass transfer, mass loss) limit the size of thesupergiant to give it a higher surface temperature than an isolated starat the same core evolutionary stage. We also discuss the possibility ofthis variable being a long-period Cepheid.Based on data acquired using the Large Binocular Telescope (LBT). TheLBT is an international collaboration among institutions in the UnitedStates, Italy and Germany. LBT Corporation partners are The Universityof Arizona on behalf of the Arizona university system; IstitutoNazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany,representing the Max-Planck Society, the Astrophysical InstitutePotsdam, and Heidelberg University; The Ohio State University, and TheResearch Corporation, on behalf of The University of Notre Dame,University of Minnesota, and University of Virginia.
| Programmsterne: Beobachtungen erwuenscht.
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| Programmsterne: Beobachtungen erwuenscht.
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| TYC 1031 01262 1: the first known Galactic eclipsing binary with a Type II Cepheid component
We present the discovery and CCD observations of the first eclipsingbinary with a Type II Cepheid component in our Galaxy. The pulsation andorbital periods are found to be 4.1523 and 51.38 d, respectively, i.e.this variable is the system with the shortest orbital period among knownCepheid binaries. Pulsations dominate the brightness variations. Theeclipses are assumed to be partial. The EB-subtype eclipsing light curveleads us to believe that the binary components are non-spherical.
| Zwischenbericht der Beobachtungskampagnen BM Cas und V1918 Cyg.
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| Liebe BAVer.
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| Wer beobachtet mit? BM Cas.
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| Interessante Bedeckungsveraenderliche: WY Leo, KN Per, BM Cas.
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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.
| New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
| SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
| Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
| The association of IRAS sources and 12CO emission in the outer Galaxy
We have revisited the question of the association of CO emission withIRAS sources in the outer Galaxy using data from the FCRAO Outer GalaxySurvey (OGS). The availability of a large-scale high-resolution COsurvey allows us to approach the question of IRAS-CO associations from anew direction - namely we examined all of the IRAS sources within theOGS region for associated molecular material. By investigating theassociation of molecular material with random lines of sight in the OGSregion we were able to construct a quantitative means to judge thelikelihood that any given IRAS-CO association is valid and todisentangle multiple emission components along the line of sight. Thepaper presents a list of all of the IRAS-CO associations in the OGSregion. We show that, within the OGS region, there is a significantincrease ( ~ 22%) in the number of probable star forming regions overprevious targeted CO surveys towards IRAS sources. As a demonstration ofthe utility of the IRAS-CO association table we present the results ofthree brief studies on candidate zone-of-avoidance galaxies with IRAScounterparts, far outer Galaxy CO clouds, and very bright CO clouds withno associated IRAS sources. We find that ~ 25% of such candidate ZOAGsare Galactic objects. We have discovered two new far outer Galaxystar-forming regions, and have discovered six bright molecular cloudsthat we believe are ideal targets for the investigation of the earlieststages of sequential star formation around HII regions. Finally, thispaper provides readers with the necessary data to compare othercatalogued data sets with the OGS data.Tables 1, 2 and A1 are only available in electronic form at the CDS viaanonymous ftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/1083
| The MACHO Project Large Magellanic Cloud Variable Star Inventory. XII. Three Cepheid Variables in Eclipsing Binaries
We present a method for solving the light curve of an eclipsing binarysystem that contains a Cepheid variable as one of its components as wellas the solutions for three eclipsing Cepheids in the Large MagellanicCloud (LMC). A geometric model is constructed in which the componentstars are assumed to be spherical and on circular orbits. The emergentsystem flux is computed as a function of time, with the intrinsicvariations in temperature and radius of the Cepheid treatedself-consistently. Fitting the adopted model to photometricobservations, incorporating data from multiple bandpasses, yields asingle parameter set best describing the system. This method is appliedto three eclipsing Cepheid systems from the MACHO project LMC database:MACHO 6.6454.5, 78.6338.24, and 81.8997.87. A best-fit value is obtainedfor each system's orbital period and inclination and for the relativeradius, color, and limb-darkening coefficients of each star. Pulsationperiods and parameterizations of the intrinsic color variations of theCepheids are also obtained, and the amplitude of the radial pulsation ofeach Cepheid is measured directly. The system 6.6454.5 is found tocontain a 4.97 day Cepheid, which cannot be definitely classified astype I or type II, with an unexpectedly brighter companion. The system78.6338.24 consists of a 17.7 day, W Virginis class type II Cepheid witha smaller, dimmer companion. The system 81.8997.87 contains anintermediate-mass, 2.03 day overtone Cepheid with a dimmer, red giantsecondary.
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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| Einige interessante Bedeckungsveraenderliche.
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| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| 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.
| The Supergiant Binary BM CAS
Attracted by an earlier claim (Thiessen 1956) that BM Cas is aneclipsing binary with one component a classical Cepheid, we haveobtained new photometry and IUE ultraviolet spectra of the system. Whilewe verify that there is variability in addition to the eclipses, weconclude that there is no classical Cepheid present. The variability isirregular, and, since it is present in the uv spectra as well as in theV photometry, we believe it is associated with the hotter component. Wefind the latter to be a high-luminosity star of spectral type of A6, inclose agreement with the MK assignment of A7 Iab (Bidelman 1982), andthe secondary component most likely to be a late-K or early-M giant. Thelatter appears to fill or nearly fill it Roch lobe, while the primarystar is not far from doing so as well, implying a complex evolutionaryhistory for the syste. (SECTION: Stars)
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| 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.
| On light curve modeling of high-inclination binary systems with accretion disks
V light curves were calculated using a model of a binary system, seen atinclination close to 90 degrees and containing an optically thickaccretion disk. Three such generated light curves, differing in the diskcontribution, were used to obtain the best solution with theWilson-Devinney code. Application of a model, which does not account forthe disk presence, produces a good fit to input data but leads tospurious values for the star parameters, particularly for the systemmass ratio. In case when the disk light is relatively low, modeling ofthe light curves of high inclination systems in which an optically thickaccretion disk completely obscures the accreting star, using a modelwhich does not account for the disk effects, results in contactconfiguration. We suggest that this may be the case for somelong-period, beta Lyr-type, binary systems.
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| Sað Açýklýk: | 00h54m45.95s |
| Yükselim: | +64°05'05.2" |
| Görünürdeki Parlaklýk: | 8.919 |
| Uzaklýk: | 1724.138 parsek |
| özdevim Sað Açýklýk: | -2 |
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