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The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics
Context: Ages, chemical compositions, velocity vectors, and Galacticorbits for stars in the solar neighbourhood are fundamental test datafor models of Galactic evolution. The Geneva-Copenhagen Survey of theSolar Neighbourhood (Nordström et al. 2004; GCS), amagnitude-complete, kinematically unbiased sample of 16 682 nearby F andG dwarfs, is the largest available sample with complete data for starswith ages spanning that of the disk. Aims: We aim to improve theaccuracy of the GCS data by implementing the recent revision of theHipparcos parallaxes. Methods: The new parallaxes yield improvedastrometric distances for 12 506 stars in the GCS. We also use theparallaxes to verify the distance calibration for uvby? photometryby Holmberg et al. (2007, A&A, 475, 519; GCS II). We add newselection criteria to exclude evolved cool stars giving unreliableresults and derive distances for 3580 stars with large parallax errorsor not observed by Hipparcos. We also check the GCS II scales of T_effand [Fe/H] and find no need for change. Results: Introducing thenew distances, we recompute MV for 16 086 stars, and U, V, W,and Galactic orbital parameters for the 13 520 stars that also haveradial-velocity measurements. We also recompute stellar ages from thePadova stellar evolution models used in GCS I-II, using the new valuesof M_V, and compare them with ages from the Yale-Yonsei andVictoria-Regina models. Finally, we compare the observed age-velocityrelation in W with three simulated disk heating scenarios to show thepotential of the data. Conclusions: With these revisions, thebasic data for the GCS stars should now be as reliable as is possiblewith existing techniques. Further improvement must await consolidationof the T_eff scale from angular diameters and fluxes, and the Gaiatrigonometric parallaxes. We discuss the conditions for improvingcomputed stellar ages from new input data, and for distinguishingdifferent disk heating scenarios from data sets of the size andprecision of the GCS.Full Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/501/941
| A dynamical study of 12 wide visual binaries
We have carried out the first dynamical studies of the relative motionsof the components of 12 wide binaries: ADS 497, ADS 2427 (GL 130.1), ADS3593, ADS 5436, ADS 6646, ADS 6783, ADS 9559 ( ? Boo), ADS 10329,ADS 10759 ( ? Dra), ADS 14878, ADS 15229, and ADS 16558. Theanalysis is based on series of photographic observations made with the26-inch refractor of Pulkovo Observatory, supplemented by data from theWDS Catalog, radial velocities and HIPPARCOS parallaxes. We used theparameters of the apparent motions, which can yield the orbit and massof a binary from observations over a short arc of the orbit of the orderof 5°-10°. The orbits and masses for six stars withorbital periods from 500 to 20 000 years have been reliably determined.For five stars with periods from 2000 to 100 000 years, we obtainedprobable orbits and mass estimates. For ADS 497 and ADS 10329, the massexcesses in their systems are 1 and 3 M ?, respectively,relative to the masses expected from the mass-luminosity dependence. Inthree cases, for ADS 3593, ADS 14878, and ADS 16558, the obtainedestimates of the total mass of the components are 46, 25, and 7300 M?, respectively, if the parallaxes are correct. Aperturbation with amplitude 0.3? and period 40 yrs has beendetected in the orbital motion of the system ADS 10759, possiblyindicating the presence of an invisible satellite with a mass of theorder of 0.4 M ?. The orientations of the orbits in theGalactic reference frame have been determined for all 12 binaries. Theplanes of most of the obtained orbits are steeply inclined to the planeof the Galaxy, as was noted in previous studies.
| New Distant Companions to Known Nearby Stars. II. Faint Companions of Hipparcos Stars and the Frequency of Wide Binary Systems
We perform a search for faint, common proper motion companions ofHipparcos stars using the recently published Lépine-Shara ProperMotion-North catalog of stars with proper motionμ>0.15'' yr-1. Our survey uncovers a totalof 521 systems with angular separations3''<Δθ<1500'', with 15 triplesand 1 quadruple. Our new list of wide systems with Hipparcos primariesincludes 130 systems identified here for the first time, including 44 inwhich the secondary star has V>15.0. Our census is statisticallycomplete for secondaries with angular separations20''<Δθ<300'' and apparentmagnitudes V<19.0. Overall, we find that at least 9.5% of nearby(d<100 pc) Hipparcos stars have distant stellar companions withprojected orbital separations s>1000 AU. We observe that thedistribution in orbital separations is consistent with Öpik's law,f(s)ds~s-1ds, only up to a separation s~4000 AU, beyond whichit follows a more steeply decreasing power law f(s)ds~s-ldswith l=1.6+/-0.1. We also find that the luminosity function of thesecondaries is significantly different from that of the single stars'field population, showing a relative deficiency in low-luminosity(8
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Doppler tomography of the transient X-ray binary Centaurus X-4 in quiescence
We present ESO-NTT low resolution spectroscopy of the neutron star X-raytransient Cen X-4 in quiescence over a complete orbital cycle. Our datareveal the presence of a K3-7 V companion which contributes 63% to the5600-6900 Å flux and orbits the neutron star with a velocitysemi-amplitude of K_2=145.8± 1.0 km s-1. This,combined with a previous determination of the inclination angle and massratio, yields a neutron star and companion mass ofM_1=1.5±1.0~Mȯ andM_2=0.31±0.27~Mȯ, respectively. The mass donor isthus undermassive for the inferred spectral type indicating it isprobably evolved, in agreement with previous studies. Doppler tomographyof the Hα line shows prominent emission located on the companionand a slightly asymmetric accretion disc distribution similar to thatseen in systems with precessing eccentric discs. Strong Hαemission from the companion can be explained by X-ray irradiation fromthe primary. No evidence is found for a hot spot in Hα, whereasone is revealed via Doppler tomography of the HeI lines. This can beinterpreted as the hot spot and outer regions of the disc being at ahigher temperature than in other systems.
| A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)
The LSPM catalog is a comprehensive list of 61,977 stars north of theJ2000 celestial equator that have proper motions larger than 0.15"yr-1 (local-background-stars frame). The catalog has beengenerated primarily as a result of our systematic search for high propermotion stars in the Digitized Sky Surveys using our SUPERBLINK software.At brighter magnitudes, the catalog incorporates stars and data from theTycho-2 Catalogue and also, to a lesser extent, from the All-SkyCompiled Catalogue of 2.5 million stars. The LSPM catalog considerablyexpands over the old Luyten (Luyten Half-Second [LHS] and New LuytenTwo-Tenths [NLTT]) catalogs, superseding them for northern declinations.Positions are given with an accuracy of <~100 mas at the 2000.0epoch, and absolute proper motions are given with an accuracy of ~8 masyr-1. Corrections to the local-background-stars propermotions have been calculated, and absolute proper motions in theextragalactic frame are given. Whenever available, we also give opticalBT and VT magnitudes (from Tycho-2, ASCC-2.5),photographic BJ, RF, and IN magnitudes(from USNO-B1 catalog), and infrared J, H, and Ks magnitudes(from 2MASS). We also provide an estimated V magnitude and V-J color fornearly all catalog entries, useful for initial classification of thestars. The catalog is estimated to be over 99% complete at high Galacticlatitudes (|b|>15deg) and over 90% complete at lowGalactic latitudes (|b|>15deg), down to a magnitudeV=19.0, and has a limiting magnitude V=21.0. All the northern starslisted in the LHS and NLTT catalogs have been reidentified, and theirpositions, proper motions, and magnitudes reevaluated. The catalog alsolists a large number of completely new objects, which promise to expandvery significantly the census of red dwarfs, subdwarfs, and white dwarfsin the vicinity of the Sun.Based on data mining of the Digitized Sky Surveys (DSSs), developed andoperated by the Catalogs and Surveys Branch of the Space TelescopeScience Institute (STScI), Baltimore.Developed with support from the National Science Foundation (NSF), aspart of the NASA/NSF NStars program.
| Optical spectroscopy of flares from the black hole X-ray transient A0620-00 in quiescence
We present a time-resolved spectrophotometric study of the opticalvariability in the quiescent soft X-ray transient A0620-00. Superimposedon the double-humped continuum light curve are the well-known flareevents, which last tens of minutes. Some of the flare events that appearin the continuum light curve are also present in the emission-line lightcurves. From the Balmer line flux and variations, we find that thepersistent emission is optically thin. During the flare event at phase1.15 the Balmer decrement dropped, suggesting either a significantincrease in temperature or that the flares are optically thicker thanthe continuum. The data suggests that there are two HI emitting regions,the accretion disc and the accretion stream-disc region, with differentBalmer decrements. The orbital modulation of H? with the continuumsuggests that the steeper decrement is most likely associated with thestream-disc impact region.By isolating the spectrum of the flare we find that it has a frequencypower-law index of -1.40 +/- 0.20 (90 per cent confidence). The flarespectrum can also be described by an optically thin gas with atemperature in the range 10000-14000 K that covers 0.05-0.08 per cent(90 per cent confidence) of the surface of the accretion disc. Giventhese parameters, the possibility that the flares arise from thebright-spot cannot be ruled out.We construct Doppler images of the H? and H? emission lines.Apart from showing enhanced blurred emission at the region where thestream impacts the accretion disc, the maps also show significantextended structure from the opposite side of the disc. The trailedspectra show characteristic S-wave features that can be interpreted inthe context of an eccentric accretion disc.
| Hubble Space Telescope WFPC2 Study of the Trapezium Cluster: The Influence of Circumstellar Disks on the Initial Mass Function
We have performed the first measures of mass accretion rates in the coreof the Orion Nebula Cluster. Four adjacent fields centered on theTrapezium stars have been imaged in the U and B bands using the WideField Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope. Weobtained photometry for 91 stars in the U band (F336W) and 71 stars inthe B band (F439W). The WFPC2 archive was also searched to obtaincomplementary V-band (F547M) and I-band (F791W) photometry. In thispaper we focus our attention on a group of 40 stars with known spectraltypes and complete UBVI WFPC2 photometry. We locate each star on the H-Rdiagram, considering both the standard ISM reddening law withRV=3.1 and the ``anomalous'' reddening law withRV=5.5 more appropriate for the Orion Nebula. Then we derivethe stellar masses and ages by comparing with the evolutionary tracksand isochrones calculated by D'Antona & Mazzitelli and Palla &Stahler. Approximately three-quarters of the sources show excessluminosity in the U band, which we attribute to mass accretion. Theknown correlation between the U-band excess and the total accretionluminosity, recalibrated for our photometric system, allows us toestimate the accretion rates, which are all found to be in the range10-8 to 10-12 Msolar yr-1.For stars older than 1 Myr, there is some evidence of a relation betweenmass accretion rates and stellar age. Overall, mass accretion ratesappear lower than those measured by other authors in the Orion flankingfields or in Taurus-Auriga. Mass accretion rates remain low even in thevicinity of the 10-5 Msolar yr-1 birthline of Palla & Stahler, suggesting that in the core of theTrapezium cluster, disk accretion has been recently depressed by anexternal mechanism. We suggest that the UV radiation generated by theTrapezium OB stars, responsible for the disk evaporation, may also causethe drop of the mass accretion rate. In this scenario, low-mass starsmay terminate their pre-main-sequence evolution with masses lower thanthose they would have reached if disk accretion could have proceededundisturbed until the final disk consumption. In OB associations thelow-mass end of the initial mass function (IMF) may therefore beaffected by the rapid evolution of the most massive cluster's stars,causing a surplus of ``accretion-aborted,'' very low mass stars andbrown dwarfs and a deficit of intermediate-mass stars. This trend is inagreement with recent observations of the IMF in the Trapezium cluster.Based on observations taken with the NASA/ESA Hubble Space Telescope,which is operated by the Association of Universities for Research inAstronomy (AURA), Inc., under NASA contract NAS5-26555.
| 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
| New Hipparcos-based Parallaxes for 424 Faint Stars
We present a catalog of 424 common proper-motion companions to Hipparcosstars with good (>3 σ) parallaxes, thereby effectively providingnew parallaxes for these companions. Compared with typical stars in theHipparcos catalog, these stars are substantially dimmer. The catalogincludes 20 white dwarfs and an additional 29 stars withMV>14, the great majority of the latter being M dwarfs.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| Rotational broadening and Doppler tomography of the quiescent X-ray nova Centaurus X-4
We present high- and intermediate-resolution spectroscopy of the X-raynova Centaurus X-4 during its quiescent phase. Our analysis of theabsorption features supports a K3-K5 V spectral classification for thecompanion star, which contributes ~=75 per cent of the total flux atHα. Using the high-resolution spectra we have measured therotational broadening of the secondary star to bevsini=43+/-6kms-1 and determined a binary mass ratio ofq=0.17+/-0.06. Combining our results for K2 and q with thepublished limits for the binary inclination, we constrain the mass ofthe compact object and the secondary star to the ranges0.49
| VLT spectroscopy of XTE J2123-058 during quiescence: the masses of the two components
We present Very Large Telescope (VLT) low-resolution spectroscopy of theneutron star X-ray transient XTE J2123-058 during its quiescent state.Our data reveal the presence of a K7V companion which contributes 77 percent to the total flux at λ6300 and orbits the neutron star atK2=287+/-12kms-1. Contrary to other soft X-raytransients (SXTs), the Hα emission is almost exactly inantiphase with the velocity curve of the optical companion. Using thelight-centre technique we obtain K1=140+/-27kms-1and henceq=K1/K2=M2/M1=0.49+/-0.10.This, combined with a previous determination of the inclination angle(i=73°+/-4°) yields M1=1.55+/-0.31Msolarand M2=0.76+/-0.22Msolar. M2 agreeswell with the observed spectral type. Doppler tomography of the Hαemission shows a non-symmetric accretion disc distribution mimickingthat seen in SW Sex stars. Although we find a large systemic velocity of- 110+/-8kms-1 this value is consistent with the galacticrotation velocity at the position of J2123-058, and hence a halo origin.The formation scenario of J2123-058 is still unresolved.
| Statistics of spectroscopic sub-systems in visual multiple stars
A large sample of visual multiples of spectral types F5-M has beensurveyed for the presence of spectroscopic sub-systems. Some 4200 radialvelocities of 574 components were measured in 1994-2000 with thecorrelation radial velocity meter. A total of 46 new spectroscopicorbits were computed for this sample. Physical relations are establishedfor most of the visual systems and several optical components areidentified as well. The period distribution of sub-systems has a maximumat periods from 2 to 7 days, likely explained by a combination of tidaldissipation with triple-star dynamics. The fraction of spectroscopicsub-systems among the dwarf components of close visual binaries withknown orbits is similar to that of field dwarfs, from 11% to 18% percomponent. Sub-systems are more frequent among the components of widevisual binaries and among wide tertiary components to the known visualor spectroscopic binaries - 20% and 30%, respectively. In triple systemswith both outer (visual) and inner (spectroscopic) orbits known, we findan anti-correlation between the periods of inner sub-systems and theeccentricities of outer orbits which must be related to dynamicalstability constraints. Tables 1, 2, and 6 are 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/382/118
| 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
| Photometric Measurements of the Fields of More than 700 Nearby Stars
In preparation for optical/IR interferometric searches for substellarcompanions of nearby stars, we undertook to characterize the fields ofall nearby stars visible from the Northern Hemisphere to determinesuitable companions for interferometric phase referencing. Because theKeck Interferometer in particular will be able to phase-reference oncompanions within the isoplanatic patch (30") to about 17th magnitude atK, we took images at V, r, and i that were deep enough to determine iffield stars were present to this magnitude around nearby stars using aspot-coated CCD. We report on 733 fields containing 10,629 measurementsin up to three filters (Gunn i, r and Johnson V) of nearby stars down toabout 13th magnitude at V.
| The ROSAT all-sky survey catalogue of the nearby stars
We present X-ray data for all entries of the Third Catalogue of NearbyStars \cite[(Gliese & Jahreiss 1991)]{gli91} that have been detectedas X-ray sources in the ROSAT all-sky survey. The catalogue contains1252 entries yielding an average detection rate of 32.9 percent. Inaddition to count rates, source detection parameters, hardness ratios,and X-ray fluxes we also list X-ray luminosities derived from Hipparcosparallaxes. Catalogue also available at CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Parallaxes and Proper Motions. XX.
Parallaxes and proper motions are listed for 48 stars in 14 fields inthe course of the ongoing astrometric program at Wesleyan and YaleUniversities. A number of resolved binary stars are included in thelist.
| Photometric Separation of Stellar Properties Using SDSS Filters
Using synthetic photometry of Kurucz model spectra, we explore thecolors of stars as a function of temperature, metallicity, and surfacegravity with Sloan Digital Sky Survey (SDSS) filters, u'g'r'i'z'. Thesynthetic colors show qualitative agreement with the few publishedobservations in these filters. We find that the locus of synthetic starsis basically two-dimensional for 4500 < T < 8000 K, whichprecludes simultaneous color separation of the three basic stellarcharacteristics we consider. Colors including u' contain the mostinformation about normal stellar properties; measurements in this filterare also important for selecting white dwarfs. We identify two differentsubsets of the locus in which the loci separate by either metallicity orsurface gravity. For 0.5 < g' - r' < 0.8 (corresponding roughly toG stars), the locus separates by metallicity; for photometric error of afew percent, we estimate metallicity to within ~0.5 dex in this range.In the range -0.15 < g' - r' < 0.00 (corresponding roughly to Astars), the locus shows separation by surface gravity. In both cases, weshow that it is advantageous to use more than two colors whendetermining stellar properties by color. Strategic observations in SDSSfilters are required to resolve the source of a ~5% discrepancy betweensynthetic colors of Gunn-Stryker stars, Kurucz models, and externaldeterminations of the metallicities and surface gravities. The syntheticstar colors can be used to investigate the properties of any normal starand to construct analytic expressions for the photometric prediction ofstellar properties in special cases.
| The mass ratio of Nova MUSCAE 1991
We report intermediate resolution H alpha spectroscopy of the black holecandidate Nova Muscae 1991 during quiescence. We classify the companionstar as a K3-K4V which contributes 85 plusmn 6 percent to the total fluxfrom the binary. The photospheric absorption lines are broadened by 106plusmn 13 km s^-1 with respect to template field stars, leading to asystem mass ratio of q = M_1/M_2 = 7.8^+3.4_-2.0. Doppler imaging of theH alpha line shows strong emission coming from the secondary star (EW =3.1 plusmn 0.6 Angstrom) which we associate with chromospheric activity.However, the hot-spot is not detected and this may indicate a lower masstransfer rate than in other X-ray transients of comparable orbitalperiods. The surface brightness distribution of the accretion disk in Halpha follows a relation I propto R^-1.1, less steep than typicallyobserved in cataclysmic variables. Updated system parameters are alsopresented.
| Dynamical studies of nine wide visual binaries in the solar neighborhood
Not Available
| Lithium in black hole binaries: the case of X-ray Nova MUSCAE 1991
We report the detection of the LiI lambda6708 resonance line in the K4Vsecondary of the black-hole binary Nova Muscae 1991. The LiI featurechanges with orbital phase, being stronger (EW ~ 400 mAngstrom) aroundphi=0.0 (observing the dark side of the secondary) and weaker (EW <=190 mAngstrom) around phi=0.5 (observing the side facing the compactobject). This effect is interpreted as LiI ionization induced byUV/X-ray illumination of the inner hemisphere of the companion star.From the strength of the LiI feature observed around phi=0.0 we infer aphotospheric lithium abundance of logN(Li) ~ 3. This value should beconsidered in fact as a lower limit to the true Li abundance because wehave not fully corrected for the LiI overionization expected fromUV/X-ray illumination. High lithium abundances are becoming a commonfeature in the secondaries of black hole binaries. After the Lidetections in V404 Cyg, A0620-00 and GS2000+25, our observations of NovaMuscae not only add a new case to the list, but also demonstrate theimpact of irradiation on the formation of the LiI line for the firsttime. The LiI features observed in the other black hole binaries areprobably also affected by irradiation, although not as strongly as inNova Muscae, and their Li abundances are higher than previously thought.The most attractive scenario for explaining the origin of the high Liabundances in black hole binaries appears to be nucleosynthesis duringthe explosive accretion events that characterize these objects. We arguethat our LiI detection in the secondary of X-ray Nova Muscae 1991, andthe transient gamma-ray narrow emission feature at 476 keV observedduring the 1991 outburst, are both signatures of Li production aroundthe black hole. We propose that the gamma-ray emission line was due to7Be electron capture which yielded excited 7Li atoms. This reaction isable to account for the central energy, narrow width and time scale ofthe observed gamma-ray emission feature. The presence of Li on thesurface of the secondary shows that Li atoms created during the outburstcan escape and enrich the interstellar medium.
| A coordinated campaign of the intermediate polar AE aqr. 1: The system parameters
We report intermediate resolution spectroscopy (50 km/s) of the magneticCataclysmic Variable AE Aqr performed as part of the World AstronomyDays (WAD) campaign. Our analysis of the absorption features supports aK4 classification for the companion star, which contributes more than95% of the total flux in the range 600-700 nm. We find that thecompanion star fills its Roche lobe since we detect a 10% modulation inthe rotational broadening (V sin i) of the absorption fines, due to thechanging geometry. Model fitting to the V sin i(phi) curve enables us tomeasure directly the system inclination (i = 58 +/- 6 deg) and thegravity darkening coefficient (beta = 0.08 +/- 0.01). Improved orbitalparameters are also presented, including an updated mass ratio (q =K1/K2 = 0.630 +/- 0.012) based upon ourK2 value and the spin-pulse delay. An independentdetermination of q is also provided by correcting the phase-averaged Vsin i for non-spherical effects. The need for these two values to agreeconstrain the limb-darkening coefficient to be epsilon approximatelyequal to 0.40 (for beta = 0.08). The component masses derived from ourvalues of K2, q and i are M1 = 0.79 +/- 0.16 solarmass units and M2 = 0.50 +/- 0.10 solar mass units. Inaddition, we do not see spectral evidence of irradiation effects.
| 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.
| Radial velocities of the components of wide visual double stars
Not Available
| Radial velocities of the components of wide visual double stars.
Not Available
| Optical spectrophotometry of oscillations and flickering in AE Aquarii
We observed rapid variations in the nova-like cataclysmic variable AEAquarii for 1.7 hr with 4.3 s time resolution using the 30-channel(3227-10494 A) spectrophotometer on the Hale 5 m telescope. The 16.5 and33.0 s oscillations show a featureless blue spectrum that can berepresented by a blackbody with temperature and area much smaller thanthe accretion disk. Models consisting of the sum of a K star spectrumand a hydrogen slab in LTE at T = 6000-10,000 K can fit the spectrum ofAE Aquarii reasonably well. The spectrum of a flare indicates opticallythin gas with T = 8000-12,000 K. The energy released by the flare islarge compared to typical stellar flares.
| Theoretical colours and isochrones for some Hubble Space Telescope colour systems. II
A grid of synthetic surface brightness magnitudes for 14 bandpasses ofthe Hubble Space Telescope Faint Object Camera is presented, as well asa grid of UBV, uvby, and Faint Object Camera surface brightnessmagnitudes derived from the Gunn-Stryker spectrophotometric atlas. Thesynthetic colors are used to examine the transformations between theground-based Johnson UBV and Stromgren uvby systems and the Faint ObjectCamera UBV and uvby. Two new four-color systems, similar to theStromgren system, are proposed for the determination of abundance,temperature, and surface gravity. The synthetic colors are also used tocalculate color-magnitude isochrones from the list of theoretical tracksprovided by VandenBerg and Bell (1990). It is shown that by using theappropriate filters it is possible to minimize the dependence of thiscolor difference on metallicity. The effects of interstellar reddeningon various Faint Object Camera colors are analyzed as well as theobservational requirements for obtaining data of a given signal-to-noisefor each of the 14 bandpasses.
| The chromospheric emission-age relation for stars of the lower main sequence and its implications for the star formation rate
An attempt is made to formulate the relationship between age andchromospheric emission (CE) in late-type dwarf stars. Evidence isreviewed that a deterministic relationship of this type actually exists,and that for stars of known age, either a power-law relation or a curvecorresponding to a constant star formation rate fits equally well.Further observations should be able to demonstrate either that there isa real excess of young stars near the sun or that the evolution of CEfor a low-mass star goes through a slow initial decline, a rapid declineat intermediate ages, and finally a slow decline for old stars like thesun.
| CA II H and K measurements made at Mount Wilson Observatory, 1966-1983
Summaries are presented of the photoelectric measurements of stellar CaII H and K line intensity made at Mount Wilson Observatory during theyears 1966-1983. These results are derived from 65,263 individualobservations of 1296 stars. For each star, for each observing season,the maximum, minimum, mean, and variation of the instrumental H and Kindex 'S' are given, as well as a measurement of the accuracy ofobservation. A total of 3110 seasonal summaries are reported. Factorswhich affect the ability to detect stellar activity variations andaccurately measure their amplitudes, such as the accuracy of the H and Kmeasurements and scattered light contamination, are discussed. Relationsare given which facilitate intercomparison of 'S' values with residualintensities derived from ordinary spectrophotometry, and for convertingmeasurements to absolute fluxes.
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Besorolás csoportokba:
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Pozíciós és asztrometriai adatok
| Csillagkép: | Sárkány |
| Rektaszcenzió: | 17h03m18.66s |
| Deklináció: | +59°35'07.3" |
| Vizuális fényesség: | 8.641 |
| Távolság: | 25.183 parszek |
| RA sajátmozgás: | -354.8 |
| Dec sajátmozgás: | 237.6 |
| B-T magnitude: | 10.019 |
| V-T magnitude: | 8.755 |
Katalógusok és elnevezések:
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