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Везани чланци
A search for debris discs around stars with giant planets
Eight nearby stars with known giant planets have been searched forthermal emission in the submillimetre arising from dust debris. The nullresults imply quantities of dust typically less than 0.02 Earth massesper star. Conversely, literature data for 20 Sun-like stars with debrisdiscs show that <= 5 per cent have gas giants inside a fewastronomical units - but the dust distribution suggests that nearly allhave more distant planets. The lack of overlap in these systems - i.e.few stars possess both inner planets and a disc - indicates that thesephenomena either are not connected or are mutually exclusive. Comparisonwith an evolutionary model shows that debris masses are predicted to below by the stellar ages of 2-8 Gyr (unless the colliding parent bodiesare quite distant, located beyond 100-200 au), but it remains to beexplained why stars that do have debris should preferentially only havedistant planets. A simple idea is proposed that could produce theselargely different systems, invoking a difference in the primordial discmass. Large masses promote fast gas giant growth and inwards migration,whereas small masses imply slow evolution, low-mass gas giants andoutwards migration that increases the collision rate of Kuiper Belt-likeobjects. This explanation neglects other sources of diversity betweendiscs (such as density and planetesimal composition and orbits), but itdoes have the merit of matching the observational results.
| 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
| A Survey of Nearby Main-Sequence Stars for Submillimeter Emission
We searched for submillimeter emission around 10 Vega-type stars and oneHerbig Ae star with the four-color bolometer at 1300 μm and the 19channel bolometer array at 870 μm using the Heinrich Hertz Telescopeat the Submillimeter Telescope Observatory. All of our sources wereundetected at 870 μm. In the case of HD 131156, we have a 3 σdetection at 1300 μm. We report a flux of 6.25+/-1.88 mJy for the HD131156 disk and a corresponding dust mass of 2.4+/-0.7 lunar masses.However, we did not detect HD 131156 at 870 μm, so we are cautiousabout the 1300 μm detection. We performed follow-up infraredobservations of HD 131156 using MIRLIN at the Palomar 200 inchtelescope, which resolved both components of the binary. The data arephotospheric, implying that the system does not have a hot, inner dustcomponent. We report submillimeter upper limits on fluxes for theremaining systems.
| Near-Infrared Integral Field Spectroscopy and Mid-Infrared Spectroscopy of the Starburst Galaxy M82
We present new infrared observations of the central regions of thestarburst galaxy M82. The observations consist of near-infrared integralfield spectroscopy in the H and K bands obtained with the MPE 3Dinstrument and of λ=2.4-45 μm spectroscopy from the ShortWavelength Spectrometer (SWS) onboard the Infrared Space Observatory.These measurements are used, together with data from the literature, to(1) reexamine the controversial issue of extinction, (2) determine thephysical conditions of the interstellar medium (ISM) within thestar-forming regions, and (3) characterize the composition of thestellar populations. Our results provide a set of constraints fordetailed starburst modeling, which we present in a companion paper. Wefind that purely foreground extinction cannot reproduce the globalrelative intensities of H recombination lines from optical to radiowavelengths. A good fit is provided by a homogeneous mixture of dust andsources, and with a visual extinction of AV=52 mag. The SWSdata provide evidence for deviations from commonly assumed extinctionlaws between 3 and 10 μm. The fine-structure lines of Ne, Ar, and Sdetected with SWS imply an electron density of ~300 cm-3, andabundance ratios Ne/H and Ar/H nearly solar and S/H about one-fourthsolar. The excitation of the ionized gas indicates an average effectivetemperature for the OB stars of 37,400 K, with little spatial variationacross the starburst regions. We find that a random distribution ofclosely packed gas clouds and ionizing clusters and an ionizationparameter of ~10-2.3 represent well the star-forming regionson spatial scales ranging from a few tens to a few hundreds of parsecs.From detailed population synthesis and the mass-to-K-light ratio, weconclude that the near-infrared continuum emission across the starburstregions is dominated by red supergiants with average effectivetemperatures ranging from 3600 to 4500 K and roughly solar metallicity.Our data rule out significant contributions from older, metal-richgiants in the central few tens of parsecs of M82. Based on observationswith ISO, an ESA project with instruments funded by ESA Member States(especially the PI countries: France, Germany, Netherlands, and theUnited Kingdom) and with the participation of ISAS and NASA. The SWS isa joint project of SRON and MPE.
| The Stromvil System: an Effective Combination of Two Medium-Band Photometric Systems
It is shown that the addition to the Stromgren four-color photometricsystem of three passbands at 374, 516 and 656 nm from the Vilniusphotometric system makes the combined system more universal. This newsystem, called the Stromvil system, makes it possible to classify starsof all spectral types, even in the presence of interstellar reddening.This property of the system is especially important in CCD photometry,allowing the photometric classification of very faint stars. Apreliminary calibration of the system in terms of spectral andluminosity classes, temperatures and surface gravities is available. Alist of preliminary standards for the Stromvil system in the regions ofCygnus, Aquila and near the North Celestial Pole is given.
| 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.
| SAO stars with infrared excess in the IRAS Point Source Catalog
We have undertaken a search for SAO stars with infrared excess in theIRAS Point Source Catalog. In contrast to previous searches, the entireIRAS (12)-(25)-(60) color-color diagram was used. This selection yieldeda sample of 462 stars, of which a significant number are stars withcircumstellar material. The stars selected can be identified aspre-main-sequence stars, Be stars, protoplanetary systems, post-AGBstars, etc. A number of objects are (visual) binary stars.Characteristic temperatures and IR excesses are calculated and theirrelations to spectral type are investigated.
| An optical search for Beta Pictoris-like disks around nearby stars
A coronagraphic survey of more than one hundred stars has been carriedout in a search at optical wavelengths for circumstellar materialsimilar to that found in the Beta Pictoris disk. The survey stars wereprimarily dwarfs in the spectral range A to K and most were closer than100 pc. No evidence of circumstellar material was found around any ofthe stars, suggesting that Beta Pictoris is an abnormal object,surrounded by an unusually large amount of optically scatteringmaterial.
| Fourth preliminary catalogue of stars, right ascension observed with photoelectric transit instrument (PPCP4).
Not Available
| Photoelectric photometry of bright stars in the vicinity of the North Celestial Pole
Not Available
| On the (B-V) colors of the bright stars
The possible causes of the dispersion of (B-V) colors of nearby stars inthe Bright Star Catalog are investigated. The distribution of (B-V)colors is presented for the entire range of spectral classes.Explanations for the dispersion in terms of a nonuniform distribution ofinterstellar absorbing material and a variability of metallicity areaddressed. A new statistical model for reddening by interstellar dustclouds is developed. It is concluded that extinction by nonuniforminterstellar matter is an important contribution to the reddening ofnearby stars, and that a part of the dispersion of (B-V) colors of Kand, possibly, M giants may be due to some unidentified variableproperty of those stars.
| Narrow-band photometry of late-type stars. II
This paper presents extensive narrow-band photometry in the Uppsalasystem supplementing earlier published mesurements so that data now areavailable for all late-type stars brighter than V = 6.05 and a number ofgalactic cluster members. Numerous UBV and BV measurements are alsopublished. The data are used to determine relations for the predictionof UBV intrinsic colors for late-type stars from the narrow-bandmeasurements. The main purpose of the data is to constitute the basisfor the determination of solar-neighborhood space densities of late-typestars, mainly giants of different kinds; these space densities will becombined with narrow-band data for fainter stars in the north Galacticpole region to yield the decrease of space density with distance fromthe galactic plane for many kinds of late-type stars.
| MK spectral types for some F and G stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979PASP...91...83C&db_key=AST
| Possible nearby stars brighter than tenth magnitude
Basic data are compiled for 447 stars brighter than 10th visualmagnitude which may be within 25 pc of the sun and are missing from boththe Gliese (1969) and the Woolley et al. (1970) catalogs of nearbystars. The list includes 245 stars with photometric parallaxes, 17 starswith trigonometric parallaxes, and nine stars with dynamical parallaxes,all of which parallaxes are at least 0.040 arcsec, as well as 176 likelycandidates. The stars are grouped into six categories according to thereliability of absolute-magnitude estimates and ranked within each groupon the basis of calculated distance. The distance estimates incorporatea kinematic correction to the photometric parallaxes which is based onthe size of a star's proper motion. A list of stars brighter than 10thmag which appear in the Gliese but not in the Woolley et al. catalog isalso provided to facilitate cross-reference with existing catalogs ofnearby stars.
| Low amplitude variable stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&A....54..309H&db_key=AST
| Spectral classification of the bright F stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88...95C&db_key=AST
| Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
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Посматрања и Астрометриски подаци
| Сазвежђа: | Велики медвед |
| Ректацензија: | 09h34m53.60s |
| Deклинација: | +72°12'20.0" |
| Apparent магнитуда: | 5.72 |
| Даљина: | 49.85 parsecs |
| Proper motion RA: | 71.8 |
| Proper motion Dec: | -74.7 |
| B-T magnitude: | 6.376 |
| V-T magnitude: | 5.827 |
Каталог и designations:
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INHABITED SKY
