Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
The Second Byurakan Survey. General Catalogue
The Second Byurakan Survey (SBS) General Catalogue is presented. TheSBS, a continuation of the Markarian survey reaching fainter limitingmagnitudes, is the first survey which combines the search of galaxiesand QSOs. A total area of 991OS#square;degrees of the Northern sky wascovered with the use of three objective prisms in combination withSchott filters. The limited magnitude on the best plates reached B ~19.5.The General Catalogue consists of 3563 objects presented in two parts: aCatalogue of galaxies (1863 objects) and one of stellar objects (1700objects). The Catalogue of SBS AGN consists of 761 objects (155 SyG, 596QSOs, and 10 BLLac). Multi-wavelength data are presented for 1438 SBSobjects identified with X-ray, IRAS and FIRST sources.Spectrophotometric observations obtained over 26 years are available for3132 objects. Redshifts were measured for ~ 2100 extragalactic objects.Spectral classification is presented for ~ 2970 objects. The majority ofthe data is presented here for the first time. The Catalogue presentsnew large homogeneous deep representative complete samples of brightQSOs, AGNs, and faint UVX galaxies in the Northern sky. The SBS sampleis found to be complete at 70% for galaxies and ~ 85% for AGN/QSOs withB ≤ 17.5.
| Structure and evolution of low-mass W UMa-type systems
The structure and evolution of low-mass W UMa-type contact binaries arediscussed by employing Eggleton's stellar evolution code. Assuming thatthese systems completely satisfy Roche geometry for contact binarieswith every kind of mass ratio (0.02-1.0) we calculate the relative radii(R1,2/A, where R1,2 are the radii of both starsand A is the orbital separation) of both components of contact binarieswith different contact depths between inner and outer Roche lobes. Weobtain a radius grid of contact binaries and can ensure the surfaces oftwo components lying on an equipotential surface by interpolation usingthis radius grid when we follow the evolution of the contact binaries.There are serious uncertainties concerning mainly the transfer of energyin these systems, i.e. it is unclear how and where the energy istransferred. We assume that the energy transfer takes place in differentregions of the common envelope to investigate the effects of the regionof energy transfer on the structure and evolution of contact binaries.We find that the region of energy transfer has a significant influenceon the structure and evolution of contact binaries, and conclude thatthe energy transfer may occur in the outermost layers of the commonconvective envelope for W-type systems, and that this transfer takesplace in the deeper layers of the common envelope for A-type systems.Meanwhile, if we assume that the energy transfer takes place in theoutermost layers for our model with low total mass, and find that ourmodel steadily evolves towards a system with a smaller mass ratio and adeeper envelope, suggesting that some A-type W UMa systems with lowtotal mass could be considered as the later evolutionary stages ofW-subtype systems, and that the surface temperature of the secondaryexceeds that of the primary during the time when the primary expandsrapidly, or the secondary contracts rapidly, suggesting that W-subtypesystems may be caused by expansion of the primary, or by the contractionof the secondary.
| Early-Type Galaxies in the Sloan Digital Sky Survey. I. The Sample
A sample of nearly 9000 early-type galaxies, in the redshift range0.01<=z<=0.3, was selected from the Sloan Digital Sky Survey(SDSS) using morphological and spectral criteria. This paper describeshow the sample was selected, presents examples of images andseeing-corrected fits to the observed surface brightness profiles,describes our method for estimating K-corrections, and shows that theSDSS spectra are of sufficiently high quality to measure velocitydispersions accurately. It also provides catalogs of the measuredphotometric and spectroscopic parameters. In related papers, these dataare used to study how early-type galaxy observables, includingluminosity, effective radius, surface brightness, color, and velocitydispersion, are correlated with one another.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| Asymptotic giant branch stars near the sun
Available red and near-infrared photometry and apparent motions of M, S,and C asymptotic giant branch (AGB) stars in the Bright Star Catalogueare tabulated and discussed. It is shown that the red and near infraredindices normally used for late-type stars are interchangeable except forcarbon stars. The M-type giants are variable with visual amplitudegreater than 0.05 mag. The reddening-free parameter m2 from Genevaphotometry is essentially a temperature parameter for M giants, whilethe reddening-free parameter d is a sensitive detector of blue stellarcompanions. The space density of AGB stars near the sun decreases by afactor of 35 in a temperature range 3800 to 3400 K. Two of the S starsnear the sun were found to have nearly equal space motions and may becomembers of the Arcturus group.
| The Pleiades supercluster in FK 5
The age distribution of the early-type supercluster members whichdominate FK 5 is studied by means of the proper motions derived byFricke et al. (1988). The main values of the total space velocity of themembers and their dependence on radial distance from the sundemonstrates the characteristic dependence of isoperiodic galacticorbits. Models incorporating convective overshoot yield a wide range ofages, and dual epochs of star formation are identified for someindividual clusters. The results of the analysis include three widepairs of premain-sequence stars, three late-type supergiants, and oneevolved close visual binary. Recent speckle observations can be utilizedto determine the orbit of the latter binary and to determine thestructure of a potential equal-component binary comprising twomain-sequence stars. Orbital and stellar parameters are listed for theclusters which make up the Pleiades supercluster including periods,cluster parallaxes, and individual masses.
| Detached to contact scenario for the origin of W UMa stars
The scenario of solar-type contact binary formation as the result ofgradual angular momentum loss from a detached or semidetached binary isinvestigated quantitatively. Angular momentum loss rate is calculated asa function of orbital period for a binary star with a total mass of 2solar masses under the assumptions that the rotational velocitydecreases as the inverse square root of the stellar age, and the totalangular momentum is decreasing due to spin-orbit coupling. Examinationof low-mass binary statistics suggests the initial period distributionof new binaries to have a smooth cut-off around 2 days. Under the aboveassumptions and that of a contact lifetime of 500 million years, it isshown that angular momentum loss could produce correct order ofmagnitude space density, period-color and cluster membership statistics.
| Accurate Optical Positions of Arakelian Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981AJ.....86..820K&db_key=AST
| Galaxies of high surface brightness
Two lists are presented which contain 621 galaxies whose surfacebrightness, as derived from their apparent magnitudes, is at least 22.0magnitudes from an area of 1 sq arcsec. The lists were compiled in anattempt to verify observationally a possible correlation between surfacebrightness and nuclear activity. Four percent of all the galaxies in anarea of 4.5 sr at declinations higher than -3 deg and galactic latitudesgreater than 20 deg are listed, including 30 Markarian, 29 Zwicky, and 7blue Haro galaxies. A morphological study of 130 of the galaxiesindicates that about half are elliptical or lenticular, 50 are compactor peculiar, and that there is an excess of elliptical and lenticularobjects in comparison with a random sample. Notes on the morphologicaltypes and colors of the galaxies are provided along with identificationcharts.
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
Kataloglar ve belirtme:
|
