Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
CCD photometric investigation of a W UMa-Type binary GSC 0763-0572
A photometric solution of an A-type W UMa binary, GSC 0763-0572,is examined with a revised orbital period. The overcontact degree isfound to be f = 40.66%, with a low mass ratio of q = 0.2554. The resultdemonstrates an unambiguous increase in the orbital period with arelative period change of ?P/P = +5.69 ×10-7 d yr-1. This indicates that GSC0763-0572 is undergoing a process of mass transfer from thesecondary component to the primary one with a rate of relative masschange of ?m1/m = +5.18 × 10-8yr-1, for a conservative model of mass transfer. Wefind that GSC 0763-0572 might transform into a rapidly rotatingstar, if total spin angular momentum increases until it is greater thanone-third of the orbital angular momentum, without breaking the contactconfiguration.
| 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.
| Mass transfer and loss of the massive semi-detached binary AI Crucis
AI Crucis is a short-period semi-detached massive close binary (P =1.41771d, Sp. = B 1.5) in the open cluster NGC 4103. It is agood astrophysical laboratory for investigating the formation andevolution of massive close binary stars via case A mass transfer.Orbital period variations of the system were analyzed based on one newlydetermined eclipse time and the others compiled from the literature. Itis discovered that the orbital period of the binary is continuouslyincreasing at a rate of dP/dt = +1.00(±0.04) ×10-7 d yr-1. After the long-termincrease is subtracted from the O - C diagram, weak evidence indicatesthe presence of a cyclic oscillation with a period of 30.1 yr, which mayreveal a very cool stellar companion in the system. The long-term periodincrease can be explained by mass transfer from the less massivecomponent to the more massive one. This is in agreement with thesemidetached configuration of the binary, indicating that the system isundergoing a slow mass-transfer stage on the nuclear time scale of thesecondary. However, it is found that the slow mass transfer isinsufficient to cause the observed period increase, which suggests thatthe stellar wind from the hot component should contribute to the amountof period increase dP/dt = +0.54 × 10-7 dyr-1 that corresponds to a mass loss rate ofM1 = 2.72 × 10-7 Modotyr-1. It is estimated that the hot component lost atotal mass of 4.1 Modot during the slow mass-transfer stage and, thus,the evolution of the binary system should be changed greatly by the massloss.
| 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).
| A systematic study of variability among OB-stars based on HIPPARCOS photometry
Context: Variability is a key factor for understanding the nature of themost massive stars, the OB stars. Such stars lie closest to the unstableupper limit of star formation. Aims: In terms of statistics, thedata from the HIPPARCOS satellite are unique because of time coverageand uniformity. They are ideal to study variability in this large,uniform sample of OB stars. Methods: We used statisticaltechniques to determine an independant threshold of variabilitycorresponding to our sample of OB stars, and then applied an automaticalgorithm to search for periods in the data of stars that are locatedabove this threshold. We separated the sample stars into 4 maincategories of variability: 3 intrinsic and 1 extrinsic. The intrinsiccategories are: OB main sequence stars (~2/3 of the sample), OBe stars(~10%) and OB Supergiant stars (~1/4).The extrinsic category refers toeclipsing binaries. Results: We classified about 30% of the wholesample as variable, although the fraction depends on magnitude level dueto instrumental limitations. OBe stars tend to be much more variable(≈80%) than the average sample star, while OBMS stars are belowaverage and OBSG stars are average. Types of variables include αCyg, β Cep, slowly pulsating stars and other types from the generalcatalog of variable stars. As for eclipsing binaries, there arerelatively more contact than detached systems among the OBMS and OBestars, and about equal numbers among OBSG stars.
| Evidence of a Massive Black Hole Companion in the Massive Eclipsing Binary V Puppis
Up to now, most stellar-mass black holes have been discovered inX-ray-emitting binaries, in which the black holes are formed through acommon-envelope evolution. Here we give evidence for the presence of amassive black hole candidate as a tertiary companion in the massiveeclipsing binary V Puppis. We found that the orbital period of thisshort-period binary (P=1.45 days) shows a periodic variation while itundergoes a long-term increase. The cyclic period oscillation can beinterpreted by the light-travel time effect via the presence of a thirdbody with a mass of no less than 10.4 Msolar. However, nospectral lines of the third body were discovered, which indicates thatit is a massive black hole candidate. The black hole candidate maycorrespond to the weak X-ray source close to V Pup, discovered by theUhuru, Copernicus, and ROSAT satellites, produced by accreting materialsfrom the massive binary via a stellar wind. The circumstellar matterwith many heavy elements around this binary may have been formed by thesupernova explosion of the progenitor of the massive black hole. All ofthe observations suggest that a massive black hole is orbiting themassive close binary V Pup with a period of 5.47 yr. Meanwhile, we foundthat the central close binary is undergoing a slow mass transfer fromthe secondary to the primary star on a nuclear timescale of thesecondary component, revealing that the system has passed through arapid mass transfer stage.
| A list of minima and maxima timings
The list contains minima of eclipsing and maxima of pulsatings stars, itcontinues the list published in OEJV 0048.
| Mass-luminosity relation for massive stars
A catalog of massive (⩾10 M ȯ) stars in binary andmultiple systems with well-known masses and luminosities has beencompiled. The catalog is analyzed using a theoretical mass-luminosityrelation. This relation allows both normal main-sequence stars and starswith peculiarities: with clear manifestations of mass transfer, massaccretion, and axial rotation, to be identified. Least-squares fittingof the observational data in the range of stellar masses 10Mȯ ⩽ M ≲ 50 M ȯ yields therelation L ˜ M 2.76.
| 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.
| Automatic classification of eclipsing binaries light curves using neural networks
In this work we present a system for the automatic classification of thelight curves of eclipsing binaries. This system is based on aclassification scheme that aims to separate eclipsing binary systemsaccording to their geometrical configuration in a modified version ofthe traditional classification scheme. The classification is performedby a Bayesian ensemble of neural networks trained with Hipparcos data ofseven different categories including eccentric binary systems and twotypes of pulsating light curve morphologies.
| The early-type eclipsing binary V1331 Aql*
We present a spectroscopic and photometric analysis of V1331 Aql, anearly-type eclipsing binary with a quite short period, i.e. 1.364 d.Radial velocity curves of both components were constructed fromhigh-dispersion spectra of this close early B-type system, which are thefirst published spectroscopic measurements of this star. The light curveanalysis is based on new UBV curves. Absolute dimensions of the binarycomponents are derived. The primary mass M1 (=10.1Msolar) and radius are close to the expected ZAMS values fortype B1V. The mass of the secondary component M2 (=5.3Msolar) corresponds to B4IV, but the component is hotter thanexpected for this type. It is oversized and overluminous for such amass, and in this respect is similar to the secondary components ofsemi-detached Algol-like systems. However, it does not completely fillits Roche lobe. A revision of the few other known binaries of comparablespectral type and period and a recalculation of the parameters of AI Cruand V Pup suggests that the detached configuration of V1331 Aql isunique among this group.
| 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.
| Updated Elements for Southern Eclipsing Binaries
Analysis of ASAS-3 data for 442 southern eclipsing binaries yielded 131stars with incorrect periods listed in the GCVS catalog
| 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/.
| 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
| 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.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Multicolour deep CCD photometric study of the moderately young southern open star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087
CCD observations in the U, B, V, R and I passbands have been used togenerate colour-colour and deep colour-magnitude diagrams for the youngopen star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087. The sampleconsists of about 2000 stars reaching down to V = 20 mag. Theinterstellar extinction across the face of the imaged cluster regionsseems to be uniform with average values of E(B-V) = 0.31, 0.34 and 0.22mag for NGC 4103, NGC 5662 and NGC 6087 respectively. The distances tothe clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087 have beenestimated as 0.5 +/- 0.05, 2.0 +/- 0.3, 0.8 +/- 0.1 and 1.0 +/- 0.1 kpcrespectively, while the corresponding ages estimated from thetheoretical stellar evolutionary isochrones fitted to the bright propermotion cluster members are ~ 100, 30, 80 and 65 Myr respectively.Present data are consistent with the membership of the Cepheid variableV Cen to NGC 5662 and of S Norm to NGC 6087. Heavy contamination byforeground and background field stars has unfortunately made itimpossible to reach definite conclusions about the faint luminosityfunction, and the data do not reach faint enough limits to investigatepre-main sequence stars. Tables 6 to 9 only available in electronic format CDS.
| Another "normal" cluster : no age spread or low-mass star deficit in NGC 4103.
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.
| OB-type binaries: Models versus observations
Recently published models on close binary evolution for massive stars (Mgreater than 5 solar mass) are compared to a set of detached andsemidetached OB binaries. For the majority of the detached systems, wefind good correspondence between theoretical and observedcharacteristics for stars with masses between 4.5 sola mass and 17 solarmass. We explore the origin of semidetached systems, and discussanomalies between models and observed characteristics. An initial massratio of around 0.6 seems to be preffered for this group. Finally, webriefly examine a number of massive (marginal) contact systems. Thelatter systems all seem to evolve according to case A of mass transfer.
| Catalogue of astrophysical parameters of binary systems
Not Available
| Temperatures from the log G - log M diagram for Algol-type binaries
The behavior of the primary and secondary components in a sample ofdouble-lined Algol-type eclipsing binaries in the log g - log Te diagramis analyzed. Results indicate that the hotter components behave likenormal main-sequence stars while the effect of irradiation may partlyexplain the 'overluminosity' of the cool components.
| Reexamination of the mass-radius relation of main sequence in binary systems
The mass-radius relation of the main sequence was reexamined using 171components of 88 double-lined detached binary systems with welldetermined absolute dimensions and masses. Empirical relations for theZAMS were obtained and compared with the theoretical models. Thepositions of the other 27 semidetached binaries in the log M - log Rdiagram are also discussed.
| Stellar masses and radii based on modern binary data
Accurate data on absolute dimensions of eclipsing binaries published inthe astronomical literature since 1980 are collected and analyzed.Simple approximation formulas relating the effective temperature withother basic physical parameters (mass, radius, bolometric magnitude) arederived. Mean and extreme values of these parameters for each spectraltype are also tabulated. The implication of improved data for theproblem of critical rotational periods and equatorial velocities ofearly-type stars is discussed.
| Angular momenta in binary systems
The correlations of angular momenta L to masses M are studied fordifferent types of spectroscopic binaries. Postulates about equivalentstates of angular momenta for different orbital parameters areintroduced. From comparisons with galaxies and single stars, it isevidenced that there is not a unique universal function L = AM exp b,when the finite structure of the relation is analyzed: each object hasits own coefficients A, b. It seems that there are an upper and a lowerlimit for all the possible functions.
| On OB-type close binary stars
Masses, radii, effective temperatures, and luminosities for thecomponents of 31 binary systems with spectral types in the O-B5 rangeare given. Comparison of the data for the 16 detached systems in thesample with main-sequence models for individual stars supports theprevious suggestion that convective overshootng and stellar-wind massloss should be included in evolutionary models. An empiricalmass-luminosity relation is derived from these detached components forthe 3.5-20 solar mass range. Eight of the remaining systems are insemidetached configurations and seven are in marginal-contact states.The results suggest that all the systems in this sample have evolved orwill evolve through a case A mass-transfer process.
| A photometric and spectroscopic study of the early-type binary AI Crucis
New Stromgren photometry and medium-dispersion spectroscopy of theearly-type eclipsing binary AI Cru are presented. The masses and radiiof the two components are found to be 9.8 + or - 0.5 and 5.8 + or - 0.3solar masses, and 4.9 + or - 0.1 and 4.4 + or - 0.1 solar radii,respectively. The semidetached nature of the system is confirmed, and itis shown by comparison with stationary models by Horn et al. (1970),that AI Cru has probably passed through the rapid phase of Case A masstransfer. It is suggested that the original system may have had a periodof about 1.3 day, and that the roles of the current primary andsecondary components were at that time reversed.
| Eclipsing binaries in open clusters. I - Preliminary study
A preliminary list of suspected eclipsing binaries in open clusters ispresented. The period, the mass ratio, the correlation between the massratio and cluster age, and the periodicity diagram are investigated.
| Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters
Not Available
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
| Сазвежђа: | Јужни крст |
| Ректацензија: | 12h06m07.69s |
| Deклинација: | -61°15'24.8" |
| Apparent магнитуда: | 9.672 |
| Proper motion RA: | -4.6 |
| Proper motion Dec: | 5.2 |
| B-T magnitude: | 9.743 |
| V-T magnitude: | 9.678 |
Каталог и designations:
|
