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מאמרים קשורים
UBV(RI)C JHK observations of Hipparcos-selected nearby stars
We present homogeneous, standardized UBV(RI)C photometry forover 700 nearby stars selected on the basis of Hipparcos parallaxes.Additionally, we list JHK photometry for about half of these stars, aswell as L photometry for 86 of the brightest. A number of stars withpeculiar colours or anomalous locations in various colour-magnitudediagrams are discussed.
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable 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/qcat?J/A+A/397/997
| The Palomar/MSU Nearby Star Spectroscopic Survey. IV. The Luminosity Function in the Solar Neighborhood and M Dwarf Kinematics
We have used new astrometric and spectroscopic observations to refinethe volume-complete sample of M dwarfs defined in previous papers inthis series. With the addition of Hipparcos astrometry, our revisedVC2 sample includes 558 main-sequence stars in 448 systems.Analysis of that data set shows no evidence of any systematic kinematicbias. Combining those data with a Hipparcos-based sample of AFGK dwarfswithin 25 pc of the Sun, we have derived the solar neighborhoodluminosity function, Φ(MV), for stars with absolutemagnitudes between -1 and +17. Using empirical and semiempiricalmass-MV relations, we transform Φ(MV) to thepresent-day mass function, ψ(M) (=dN/dM). Depending on themass-luminosity calibration adopted, ψ(M) can be represented byeither a two-component or a three-component power law. In either case,the power-law index α has a value of ~1.3 at low masses (0.1Msolar4)stars in the Hipparcos 25 pc sample are well represented bytwo-component Gaussian distributions, with ~10% of the stars in thehigher velocity dispersion component. We suggest that the lattercomponent is the thick disk, and we offer a possible explanation for therelatively low velocity dispersions shown by ultracool dwarfs.Based partly on observations made at the 60 inch (1.5 m) telescope atPalomar Mountain, which is jointly owned by the California Institute ofTechnology and the Carnegie Institution of Washington.
| An astrometric catalogue of stars in the region of M15
We present positions and proper motions with respect to the PPMcatalogue of 863 stars in a field of 8 deg x 6 deg centered on theglobular cluster M15. The catalogue is based on measurements of 136plates from the Carte du Ciel telescope of Bordeaux, the CERGA Schmidttelescope, and the double refractor of Bonn. The modal accuracy of theproper motions is +/- 0 arcsec 15/100 a.
| Dwarf K and M stars of small proper motion found in a large spectroscopic survey
More than 2000 candidates for K and M dwarf status, generally havingproper motions that are either unknown or less than 0.2 arcsec perannum, have been identified in an objective-prism survey covering theentire sky north of declination - 25 degrees and more than 10 degreesfrom the galactic plane. More than 95 percent have no previousindication that they are dwarfs. Several dozen appear to be visualdouble stars.
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | סוסון |
| התרוממות ימנית: | 21h22m26.60s |
| סירוב: | +10°52'25.5" |
| גודל גלוי: | 9.979 |
| מרחק: | 20.713 פארסק |
| תנועה נכונה: | -56.6 |
| תנועה נכונה: | 31.9 |
| B-T magnitude: | 11.832 |
| V-T magnitude: | 10.132 |
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