Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
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.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| INTEGRAL observations of the black hole candidate H 1743-322 in outburst
INTEGRAL made 3 observations in 2003 April of the black hole candidate H1743-322 during the rising part, and close to the maximum, of anoutburst. H 1743-322 was previously observed in outburst in 1977-1978.The source is located in a crowded region of the sky (l =357o, b = -2o) and at least 18 sources areclearly detected in the field of view of the ISGRI gamma-ray imagerduring a 277 ks exposure. These are well known persistent X-ray binarysources and 3 transient sources in outburst. The combined 5-200 keVJEM-X and SPI spectrum of H 1743-322 is well fit with an absorbed ((2.5+4.3 -2.5) x 1022 atom cm-2)soft (photon index 2.70 +/- 0.09) power-law model, consistent with H1743-322 being in a high/soft state.Based on observations with INTEGRAL, an ESA project with instruments andscience data centre funded by ESA member states (especially the PIcountries: Denmark, France, Germany, Italy, Switzerland, Spain), CzechRepublic and Poland and with the participation of Russia and the USA.
| ASCA X-Ray Source Catalog in the Galactic Center Region
The ASCA satellite made 107 pointing observations on a 5×5deg2 region around the center of our Galaxy from 1993 to1999. In the X-ray images of the 0.7-3 keV or 3-10 keV bands, we found52 point sources and a dozen diffuse sources. All the point sources areuniformly fitted with an absorbed power-law model. For selected brightsources, Sgr A*, AX J1745.6-2901, A1742-294, SLX 1744-300, GRO J1744-28,SLX 1737-282, GRS 1734-292, AX J1749.2-2725, KS 1741-293, GRS1741.9-2853, and an unusual flare source XTE J1739-302, we presentfurther detailed spectral and timing analyses and discuss their nature.The dozen extended X-ray sources comprise radio supernova remnants,giant molecular clouds, and some new discoveries. Most show emissionlines from either highly ionized atoms or low-ionized irons. The X-rayspectra were fitted with either a thin thermal or power-law model. Thispaper summarizes the results and provides the ASCA X-ray source catalogin the Galactic center region.
| A catalogue of soft X-ray sources in the galactic center region
We present a catalogue of 107 point-like X-ray sources derived from asystematic analysis of all the ROSAT PSPC observations of the galacticcenter region performed in 1992-1993. Besides SgrA*, the massive blackhole at the galactic center, 41 X-ray sources have been positionallyassociated with already classified objects. Twenty are identified withforeground stars and five with known Low Mass X-ray Binaries. Themajority of the sources in our catalogue still remains unidentified.They are hard and/or severely absorbed and probably represent a largepopulation of X-ray binaries located in the galactic center region,accreting at low accretion rates, and still largely unknown.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| A large, complete, volume-limited sample of G-type dwarfs. I. Completion of Stroemgren UVBY photometry
Four-colour photometry of potential dwarf stars of types G0 to K2,selected from the Michigan Spectral Catalogues (Vol. 1-3), has beencarried out. The results are presented in a catalogue containing 4247uvby observations of 3900 stars, all south of δ = -26deg. Theoverall internal rms errors of one observation (transformed to thestandard system) of a program star in the interval 8.5 < V < 10.5are 0.0044, 0.0021, 0.0039, and 0.0059, respectively, in V, b-y, m_1_ ,and c_1_. The purpose of the catalogue, combined with earliercatalogues, is to allow selection of a large, complete, volume-limitedsample of G- and K-type dwarfs, investigate their metallicitydistribution, and compare it to predictions of various models ofgalactic chemical evolution. Future papers in this series will discussthese subjects.
| 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.
| Lunar occultation of the Galactic center at 2.2 microns
Results of the lunar occultation of IRS 16 on 1986 September 11 arereported. Sixty percent of the observed flux in a 6arcsec.5 beam comesfrom four discrete sources. Three sources are unresolved pointlikeobjects (< 0arcsec.05) and are assumed to be individual stars. Thefourth object is well resolved with a diameter of 0arcsec.3 (0.01 pc).By timing the lunar occultation, the authors have identified this 9thmag object with IRS 16 NE. This blue object near the dynamical centermay be a very compact cluster of stars and thus the true center of theGalaxy.
| The Einstein galactic plane survey - Statistical analysis of the complete X-ray sample
A flux-limited survey of the galactic plane using the Einstein ImagingProportional Counter has been conducted, discovering 71 point-like X-raysources exceeding a five sigma threshold. These sources arestatistically analyzed, and it is concluded that the number-fluxrelation for low-flux galactic plane X-ray sources has a slope of -1.10,significantly steeper than the about -0.5 found for bright sources byUhuru and Ariel V. The sample contains about 46 percent coronal sources,about 31 percent extragalactic sources, and about 23 percent galacticaccretion sources. Thus, about 16 new galactic accretion sources havebeen discovered. The approximate number density of such sources isconsistent with their being cataclysmic variables and other accretingwhite dwarfs. Faint galactic plane sources are significantlyconcentrated toward the galactic bulge, and those near the bulge exhibita flatter number-flux relation than those at higher galactic latitudesand longitudes. This indicates a different source population with a lessisotropic distribution.
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Ofiuco |
| Ascensione retta: | 17h42m30.36s |
| Declinazione: | -28°44'55.6" |
| Magnitudine apparente: | 9.03 |
| Moto proprio RA: | -2.5 |
| Moto proprio Dec: | -41 |
| B-T magnitude: | 9.911 |
| V-T magnitude: | 9.103 |
Cataloghi e designazioni:
|
