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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
| The XMM-Newton bright serendipitous survey . Identification and optical spectral properties
Aims.We present the optical classification and redshift of 348 X-rayselected sources from the XMM-Newton Bright Serendipitous Survey (XBS),which contains a total of 400 objects (identification level = 87%).About 240 are new identifications. In particular, we discuss in detailthe classification criteria adopted for the active galactic nuclei(AGNs) population. Methods: By means of systematic spectroscopiccampaigns using various telescopes and through the literature search, wehave collected an optical spectrum for the large majority of the sourcesin the XBS survey and applied a well-defined classification “flowchart”. Results: We find that the AGNs represent the mostnumerous population at the flux limit of the XBS survey(~10-13 erg cm-2 s-1) constituting 80%of the XBS sources selected in the 0.5-4.5 keV energy band and 95% ofthe “hard” (4.5-7.5 keV) selected objects. Galactic sourcespopulate the 0.5-4.5 keV sample significantly (17%) and only marginally(3%) the 4.5-7.5 keV sample. The remaining sources in both samples areclusters/groups of galaxies and normal galaxies (i.e. probably notpowered by an AGN). Furthermore, the percentage of type 2 AGNs (i.e.optically absorbed AGNs with A_V>2 mag) dramatically increases goingfrom the 0.5-4.5 keV sample (f=NAGN 2/N_AGN=7%) to the4.5-7.5 keV sample (f=32%). We finally propose two simple diagnosticplots that can be easily used to obtain the spectral classification forrelatively low-redshift AGNs even if the quality of the spectrum is notgood.Based on observations collected at the Telescopio Nazionale Galileo(TNG) and at the European Southern Observatory (ESO) and on observationsobtained with XMM-Newton, an ESA science mission with instruments andcontributions directly funded by ESA Member States and the USA (NASA).Table 3 is only available in electronic form at http://www.aanda.org
| Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data
Context: .This paper is the last in a series devoted to the analysis ofthe binary content of the Hipparcos Catalogue. Aims: .Thecomparison of the proper motions constructed from positions spanning ashort (Hipparcos) or long time (Tycho-2) makes it possible to uncoverbinaries with periods of the order of or somewhat larger than the shorttime span (in this case, the 3 yr duration of the Hipparcos mission),since the unrecognised orbital motion will then add to the propermotion. Methods: .A list of candidate proper motion binaries isconstructed from a carefully designed χ2 test evaluatingthe statistical significance of the difference between the Tycho-2 andHipparcos proper motions for 103 134 stars in common between the twocatalogues (excluding components of visual systems). Since similar listsof proper-motion binaries have already been constructed, the presentpaper focuses on the evaluation of the detection efficiency ofproper-motion binaries, using different kinds of control data (mostlyradial velocities). The detection rate for entries from the NinthCatalogue of Spectroscopic Binary Orbits (S_B^9) is evaluated, as wellas for stars like barium stars, which are known to be all binaries, andfinally for spectroscopic binaries identified from radial velocity datain the Geneva-Copenhagen survey of F and G dwarfs in the solarneighbourhood. Results: .Proper motion binaries are efficientlydetected for systems with parallaxes in excess of ~20 mas, and periodsin the range 1000-30 000 d. The shortest periods in this range(1000-2000 d, i.e., once to twice the duration of the Hipparcos mission)may appear only as DMSA/G binaries (accelerated proper motion in theHipparcos Double and Multiple System Annex). Proper motion binariesdetected among S_B9 systems having periods shorter than about400 d hint at triple systems, the proper-motion binary involving acomponent with a longer orbital period. A list of 19 candidate triplesystems is provided. Binaries suspected of having low-mass(brown-dwarf-like) companions are listed as well. Among the 37 bariumstars with parallaxes larger than 5 mas, only 7 exhibit no evidence forduplicity whatsoever (be it spectroscopic or astrometric). Finally, thefraction of proper-motion binaries shows no significant variation amongthe various (regular) spectral classes, when due account is taken forthe detection biases.Full Table [see full textsee full text] is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/377
| The stellar content of the XMM-Newton bright serendipitous survey
Context: .The comparison of observed counts in a given sky directionwith predictions by Galactic models yields constraints on the spatialdistribution and the stellar birthrate of young stellar populations. TheXMM-Newton Bright Serendipitous Survey (XBSS) is an unbiased survey thatincludes a total of 58 stellar sources selected in the 0.5-4.5 keVenergy band, having a limiting sensitivity of 10-2 cnts-1 and covering an area of 28.10 sq deg. Aims: .Wepresent the results of analysing the stellar content of the XBSS so asto understand the recent star formation history of the Galaxy in thevicinity of the Sun. Methods: .We compared the observations withthe predictions obtained with XCOUNT, a model of the stellar X-raycontent of the Galaxy. The model predicts the number and properties ofthe stars to be observed in terms of magnitude, colour, population andf_x/fv ratio distributions of the coronal sources detectedwith a given instrument and sensitivity in a specific sky direction. Results: .As in other shallow surveys, we observe an excess of starsnot predicted by our Galaxy model. Comparing the colours of theidentified infrared counterparts with the model predictions, we observethat this excess is produced by yellow (G+K) stars. The study of theX-ray spectrum of each source reveals a main population of stars withthe coronal temperature stratification typical of intermediate-agestars. As no assumptions have been made for the selection of the sample,our results must be representative of the entire solar neighbourhood.Some stars show infrared excess due to circumstellar absorption, whichis indicative of youth.The XMM-Newton Bright Serendipitous Survey was conceived by theXMM-Newton Survey Science Center (SSC), a consortium of 10 institutionsappointed by ESA to help the SOC in distinct technical aspects,including the exploitation of the XMM-Newton serendipitous detections(see http://xmmssc-www.star.le.ac.uk/). Tables 2 and 3 are onlyavailable in electronic form at http://www.aanda.org
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| Spots on EK Draconis. Active longitudes and cycles from long-term photometry
We analyse photometric observations of the young active star EK Dra,altogether about 21 years. Similar to the ZAMS stars LQ Hya and AB Dor,EK Dra shows long-lived, non-axisymmetric spot distribution with activelongitudes on opposite hemispheres. At least two activity cycle can befound from the data. The first cycle originates from repeated switchesof the activity between two active longitudes in about (2-2.25)-yearintervals, resulting in a cycle of about (4-4.5) years. The second cycleis of the order of 10.5 years and comes from migration of the activelongitudes. Our data cover two consecutive cycles. The periodicity isalso present in the maximum, the mean and the minimum stellarbrightness. Additionally, there is a long-term trend. If we combine ourdata with the Sonneberg plate measurements, we can conclude that theoverall brightness of EK Dra has been continuously decreasing at leastfor the last 45 years. A comparison with current sunspot activityreveals many similarities between the Sun and EK Dra.
| Differential Photometry of EK Dra and 29 Dra
We report on BVR precise photometry of active late-type stars EK Dra and29 Dra in the spring of 2004. The analysis suggests a reasonable fitwith single spot model for both cases in the season as far as theV-curve is concerned. The spots are generally cooler than surroundingphotosphere and are at high latitudes. The maximal brightness changesfor both stars implying a non-rotating component of activity signatures,the spots. We expect that the spot configuration is stable over theperiod of approximately three months.
| Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| Exploring the X-ray sky with the XMM-Newton bright serendipitous survey
We present here ``The XMM-Newton Bright Serendipitous Survey'', composedof two flux-limited samples: the XMM-Newton Bright Source Sample (BSS,hereafter) and the XMM-Newton ``Hard'' Bright Source Sample (HBSS,hereafter) having a flux limit of f_x≃ 7 × 10-14erg cm-2 s-1 in the 0.5-4.5 keV and 4.5-7.5 keVenergy band, respectively. After discussing the main goals of thisproject and the survey strategy, we present the basic data on a completesample of 400 X-ray sources (389 of them belong to the BSS, 67 to theHBSS with 56 X-ray sources in common) derived from the analysis of 237suitable XMM-Newton fields (211 for the HBSS). At the flux limit of thesurvey we cover a survey area of 28.10 (25.17 for the HBSS) sq. deg. Theextragalactic number-flux relationships (in the 0.5-4.5 keV and in the4.5-7.5 keV energy bands) are in good agreement with previous and newresults making us confident about the correctness of data selection andanalysis. Up to now ˜ 71% (˜ 90%) of the sources have beenspectroscopically identified making the BSS (HBSS) the sample with thehighest number of identified XMM-Newton sources published so far. At theX-ray flux limits of the sources studied here we found that: a) theoptical counterpart in the majority (˜ 90%) of cases has amagnitude brighter than the POSS II limit (R ˜ 21mag);b) the majority of the objects identified so far are broad line AGN bothin the BSS and in the HBSS. No obvious trend of the source spectra (asdeduced from the Hardness Ratios analysis) as a function of the countrate is measured and the average spectra of the ``extragalactic''population corresponds to a (0.5-4.5 keV) energy spectral index of˜ 0.8 (˜ 0.64) for the BSS (HBSS) sample. Based on thehardness ratios we infer that about 13% (40%) of the sources in the BSS(HBSS) sample are described by an energy spectral index flatter thanthat of the cosmic X-ray background. Based on previous X-ray spectralresults on a small subsample of objects we speculate that all thesesources are indeed absorbed AGN with the N_H ranging from a few times1021 up to few times 1023 cm-2. We donot find strong evidence that the 4.5-7.5 keV survey is sampling acompletely different source population if compared with the 0.5-4.5 keVsurvey; rather we find that, as expected from the CXB synthesis models,the hard survey is simply picking up a larger fraction of absorbed AGN.At the flux limit of the HBSS sample we measure surface densities ofoptically type 1 and type 2 AGN of 1.63± 0.25 deg-2and 0.83± 0.18 deg-2, respectively; optically type 2AGN represent 34± 9% of the total AGN population. Finally, wehave found a clear separation, in the hardness ratio diagram and in the(hardness ratio) vs. (X-ray to optical flux ratio) diagram, betweenGalactic ``coronal emitting'' stars and extragalactic sources. Theinformation and ``calibration'' reported in this paper will make theexisting and incoming XMM-Newton catalogs a unique resource forastrophysical studies.Based on observations obtained with XMM-Newton, an ESA science missionwith instruments and contributions directly funded by ESA Member Statesand the USA (NASA). The majority of the newoptical spectroscopy data used here have been obtained using thefacilities of the Italian ``Telescopio Nazionale Galileo'' (TNG) and ofthe European Southern Observatory (ESO).Tables \ref{t2}-\ref{t4} and Appendices are only available in electronicform at http://www.edpsciences.org
| 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
| Magnetic activity of six young solar analogues I. Starspot cycles from long-term photometry
A long-term photometric monitoring of a selected sample of solaranalogues has been carried out since early nineties as part of The Sunin time project, which is aimed at a multiwavelength study of stars withsolar-like global properties, but with different ages and thus atdifferent stages of their evolution. The extended time sequence ofground-based observations collected over more than a decade as part ofthis program has revealed the existence of starspot cycles. Also fromthese data it is possible to investigate surface differential rotationof the stars. In this paper we present the photometry collected to dateand report on cycles search for a selected subsample of five youngsingle G0-G5V stars with ages between =~ 130 Myr and 700 Myr:EK Dra, pi 1 UMa, HNPeg, k1 Cet and BE Cet.Also we include in this study the Pleiades-age ( =~ 130 Myr) K0V starDX Leo (HD 82443). All the cited stars show activitycycles whose period is, furthermore, the first determined fromphotometric data. They are compared to those activity cycles derivedfrom CaII H&K emission fluxes and differences are discussed. All thecycle periods, except for EK Dra, fit well the empirical relations withglobal stellar parameters derived from larger stellar samples. Thefollowing results are also inferred from the present study: i) thefastest rotating stars tend to have longer cycles; ii) the range in theobserved cycle lengths seems to converge with stellar age from a maximumdispersion around the Pleiades' age towards the solar cycle value at theSun's age; iii) the overall short- and long-term photometric variabilityincreases with inverse Rossby number with very high correlation degree,indicating that the level of magnetic activity at least in photosphereis still controlled by the stellar rotation even on the longest timescales; iiii) the increase with inverse Rossby number of the long-termoverall photometric variability seems to level off at the highestrotation rate, which may be interpreted as due to a saturation in thelevel of photospheric magnetic activity around the activity maximum.
| EK Draconis: Long-term photometry on Sonneberg Sky-Patrol plates
We performed long-term photometry of the young solar analog EK Draconis(HD 129333) using 1030 blue-sensitive Sky-Patrol plates taken atSonneberg Observatory from 1958 onwards. A secular dimming of 0.0057+/-0.0008 mag/y beginning around 1975 was found. Hence, the recent trendfirst observed with Automatic Photoelectric Telescopes (APTs) isconfirmed and traced back to the mid-seventies.
| Speckle Interferometry of New and Problem Hipparcos Binaries. II. Observations Obtained in 1998-1999 from McDonald Observatory
The Hipparcos satellite made measurements of over 9734 known doublestars, 3406 new double stars, and 11,687 unresolved but possible doublestars. The high angular resolution afforded by speckle interferometrymakes it an efficient means to confirm these systems from the ground,which were first discovered from space. Because of its coverage of adifferent region of angular separation-magnitude difference(ρ-Δm) space, speckle interferometry also holds promise toascertain the duplicity of the unresolved Hipparcos ``problem'' stars.Presented are observations of 116 new Hipparcos double stars and 469Hipparcos ``problem stars,'' as well as 238 measures of other doublestars and 246 other high-quality nondetections. Included in these areobservations of double stars listed in the Tycho-2 Catalogue andpossible grid stars for the Space Interferometry Mission.
| Starspot photometry with robotic telescopes. UBV(RI)_C and by light curves of 47 active stars in 1996/97
We present continuous multicolor photometry for 47 stars from October1996 through June 1997. Altogether, 7073 V(RI)_c, UBV, and by datapoints, each the average of three individual readings, were acquiredwith three automatic photoelectric telescopes (APTs) at FairbornObservatory in southern Arizona. Most of our targets arechromospherically active single and binary stars of spectral type G to Kbut there are also four pre-main-sequence objects and three pulsatingstars in our sample. The light variability is generally due torotational modulation of an asymmetrically spotted stellar surface andtherefore precise rotational periods and their seasonal variations aredetermined from Fourier analysis. We also report on photometricvariations of gamma CrB (A0V) with a period of 0.44534 days. All dataare available in numerical form. All data are available from CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Program to Link the HIPPARCOS Reference Frame to an Extragalactic Reference System Using the Fine Guidance Sensors of the Hubble Space Telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2796H&db_key=AST
| The Photometric Variability of Sun-like Stars: Observations and Results, 1984--1995
Using differential Stromgren b, y photometry, we monitored thebrightness variations of 41 program stars and their 73 comparison starsfrom 1984 through 1995. The predominantly main-sequence program starsspanned ranges of temperature and mean chromospheric activity centeredon solar values. About 40% of all the stars showed measurablevariability, typically at levels below 0.01 mag (~1%), on bothnight-to-night and year-to-year timescales. The variability correlatedwith mean chromospheric activity and advancing spectral type. We presentdifferential light curves and statistical descriptions of ourobservations.
| The Spotted Young Sun - HD129333 (= EK Dra)
Not Available
| HD 129333: The Sun in its infancy
HD 129333 is a remarkable young, nearby solar-type G star which offers aunique opportunity of studying the properties of the Sun at a time veryshortly after in arrived on the main sequence. Its space motion suggestthat it is a member of the Pleiades moving group, with an age ofapproximately 70 Myr; its lithium abundance is consistent with this. HD129333 has the highest level of Ca II emission of any G star which isnot a member of a close binary. Our observations in 1983 showed it tohave low-amplitude (5%) light variations implying a rotation period ofabout 2.7 days, or about 10 times faster than the Sun. Modeling of thephotometric variations on the assumption that they are due to starspotsyields a spot temperature about 500 K cooler than the photosphere, and acoverage of about 6% of the stellar surface area. ROSAT observations in1990 revealed the star to be an X-ray source, with an X-ray luminosityin the 0.2 to 2.4 keV range about 300 times that of the Sun. We haveused International Ultraviolet Explorer (IUE) observations in conjuctionwith ground-based photometry to examine the magnetic activity of thisstar. The IUE emission-line fluxes reveal a level of chromosphericactivity 3 to 20 times greater than the Sun's. The transition-regionactivity is 20 to 100 times that of the Sun. The activity level of HD129333 is consistent with the Skumanich law relating activity to age,and with the rotation-activity relation, although it may be nearsaturation level. This star can yield valuable information about themagnetic dynamo of the young Sun, as well as about stellar dynamos ingeneral. The 1988 IUE observations covered four phases of its rotationalcycle. A phase dependence of the Mg II h and k emission flux suggests aclose association of chromospheric plages with starspot regions at thattime. Systematic variations in the mean brightness of HD 129333 between1983 and 1993, and in the UV emission fluxes, indicate the presence ofan activity cycle of an estimated 12 years' duration. HD 129333 is thefirst solar-type star other than RS CVn binaries for which luminosityvariations provide evidence for a spot cycle. Unlike the Sun, which isbrighter at activity maximum HD 129333 appears to be fainter when moreheavily spotted. Although evolutionary models for the Sun suggest thatit was about 30% less luminous at age 70 Myr, they give no informationabout the UV flux. Accordingly, we have used the 1988 IUE observationsof HD 129333 to construct a model spectrum of the infant Sun, which canbe used to provide a quantitative estimate of the UV flux in the earlysolar system.
| Gliese 559.1 - a Young Spotted Single Star
Not Available
| Meridian observations made with the Carlsberg Automatic Meridian Circle at Brorfelde (Copenhagen University Observatory) 1981-1982
The 7-inch transit circle instrument with which the present position andmagnitude catalog for 1577 stars with visual magnitudes greater than11.0 was obtained had been equipped with a photoelectric moving slitmicrometer and a minicomputer to control the entire observationalprocess. Positions are reduced relative to the FK4 system for each nightover the whole meridian rather than the usual narrow zones. Thepositions of the FK4 stars used in the least squares solution are alsogiven in the catalog.
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Наблюдательные данные и астрометрия
| Созвездие: | Дракон |
| Прямое восхождение: | 14h39m22.83s |
| Склонение: | +64°09'14.2" |
| Видимая звёздная величина: | 7.553 |
| Расстояние: | 108.108 парсек |
| Собственное движение RA: | -57.3 |
| Собственное движение Dec: | 19.5 |
| B-T magnitude: | 8.019 |
| V-T magnitude: | 7.592 |
Каталоги и обозначения:
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