Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
Observation and modelling of main-sequence star chromospheres - XV. New constraints on the dynamo mechanisms for dM1 stars
With the help of measures of rotation, radius and metallicity for aselected sample of dM1 stars (with Teff= 3460 ± 60 K),we aim to set new constraints on the dynamo mechanisms.We recover 913 high-resolution spectra for 97 different M1 dwarfs fromthe European Southern Observatory and Observatoire de Haute Provencedata bases. We present 660 new measurements of the Ca II resonance linesand 913 new measurements of the H? line for dM1 stars. We alsocompile other measurements available in the literature. In total, weobtain 2216 measures of the Ca II lines for 113 different dM1 stars.This represents the largest compilation of chromospheric linemeasurements at a single spectral type.We cross-correlate these magnetic activity indicators with variousstellar parameters to set new constraints on the dynamo mechanisms andon the properties of the outer atmosphere.We find a correlation of the Ca II line mean equivalent width with theabsolute magnitude and the metallicity. We correct the Ca II linemeasures from the metallicity effect and find that the surface flux inthe Ca II lines grows roughly as the power of 3.6 of the stellar radius.This corrected flux is a direct measure of magnetic activity at thechromospheric level. We find that the total magnetic activity levelgrows roughly as the power of 5.6 of the stellar radius. This trend isconfirmed by the correlation between the H? line and absolutemagnitude and the H? line luminosity and stellar radius: theH? luminosity grows roughly as the volume of the star for lowactivity dM1 stars and as the power of roughly 5/2 of the stellar radiusfor dM1e stars. The advantage of the H? line is that its formationin not dependent on metallicity.In contrast to the Ca II line, we find no correlation betweenLX and the absolute magnitude. We find that LXroughly correlates with the Ca II luminosity although the correlation isnot very good. This correlation shows that LX grows as thepower of 3/2 of the Ca II luminosity, i.e. the coronal emission growsfaster than the chromospheric emission.We find a correlation between the corrected Ca II line equivalent widthand P/sin i, i.e. the Ca II surface flux grows as the power of -1.5 ofthe rotation period. We also find a correlation between FX,the X-ray surface flux, and P/sin i: FX? (P/sini)-3.7. In other words, the coronal emission is much moredependent on the rotation period than the chromospheric emission.We find that the level of magnetic activity in dM1 stars is moredependent on the stellar radius than on rotation at the chromosphericlevel. We discuss the implications of these results on the models ofstellar dynamos. Based on observations available at Observatoire deHaute Provence and the European Southern Observatory data bases and onHipparcos parallax measurements.
| Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry
Astrometric surveys provide the opportunity to measure the absolutemagnitudes of large numbers of stars, but only if the individualline-of-sight extinctions are known. Unfortunately, extinction is highlydegenerate with stellar effective temperature when estimated frombroad-band optical/infrared photometry. To address this problem, Iintroduce a Bayesian method for estimating the intrinsic parameters of astar and its line-of-sight extinction. It uses both photometry andparallaxes in a self-consistent manner in order to provide anon-parametric posterior probability distribution over the parameters.The method makes explicit use of domain knowledge by employing theHertzsprung-Russell Diagram (HRD) to constrain solutions and to ensurethat they respect stellar physics. I first demonstrate this method byusing it to estimate effective temperature and extinction from BVJHKdata for a set of artificially reddened Hipparcos stars, for whichaccurate effective temperatures have been estimated from high-resolutionspectroscopy. Using just the four colours, we see the expected strongdegeneracy (positive correlation) between the temperature andextinction. Introducing the parallax, apparent magnitude and the HRDreduces this degeneracy and improves both the precision (reduces theerror bars) and the accuracy of the parameter estimates, the latter byabout 35 per cent. The resulting accuracy is about 200 K in temperatureand 0.2 mag in extinction. I then apply the method to estimate theseparameters and absolute magnitudes for some 47 000 F, G, K Hipparcosstars which have been cross-matched with Two-Micron All-Sky Survey(2MASS). The method can easily be extended to incorporate the estimationof other parameters, in particular metallicity and surface gravity,making it particularly suitable for the analysis of the 109stars from Gaia.
| Observation and modelling of main-sequence star chromospheres - XIV. Rotation of dM1 stars
We have measured v sin i for a selected sample of dM1-typestars. We give 114 measurements of v sin i for 88 different stars, andsix upper detection limits. These are the first measurements of v sin ifor most of the stars studied here. This represents the largest sampleof v sin i measurements for M dwarfs at a given spectral type. For thesemeasurements, we used four different spectrographs: HARPS (ESO), SOPHIE(OHP), ÉLODIE (OHP) and UVES (ESO). Two of these spectrographs(HARPS and SOPHIE) are particularly stable in wavelength since they weredesigned for exoplanet searches.We measured v sin i down to an accuracy of 0.3kms-1 for thehighest resolution spectrographs and a detection limit of about1kms-1. We show that this unprecedented accuracy for M dwarfsin our data set is possible because all the targets have the samespectral type. This is an advantage and it facilitates the determinationof the narrowest line profiles for v sin i ~ 0. Although it is possibleto derive the zero-point profiles using several spectral types at atime. These values were combined with other measurements taken from theliterature. The total sample represents detected rotation for 100 stars(10 dM1e and 90 dM1 stars). We confirm our finding of Paper VII that thedistribution of the projected rotation period is bimodal for dM1 starswith a much larger sample, i.e. there are two groups of stars: the fastrotators with P/sin i ~ 4.5d and the slow rotators with P/sin i ~ 14.4d.There is a gap between these two groups. We find that the distributionof stars as a function of P/sin i has two very abrupt cuts, below 10dand above 18d. There are very few stars observed out of this range10-18d. We also observe that the distribution increases slightly from 18to 10d.We find that the M1 subdwarfs (very low metallicity dwarfs) rotate withan average period of P/sin i ~ 7.2d, which is about twice faster as themain group of normal M1 dwarfs. We also find a correlation for P/sin ito decrease with stellar radius among dM1e stars. Such a trend is alsoobserved in dM1 stars.We also derive metallicity and radius for all our target stars using thesame method as in Paper VII. We notably found that 11 of our targetstars are subdwarfs with metallicities below -0.5dex.Based on observations available at Observatoire de Haute Provence andthe European Southern Observatory data bases and on Hipparcos parallaxmeasurements.E-mail: eric_houdebine@yahoo.fr
| Discoveries from a Near-infrared Proper Motion Survey Using Multi-epoch Two Micron All-Sky Survey Data
We have conducted a 4030 deg2 near-infrared proper motionsurvey using multi-epoch data from the Two Micron All-Sky Survey(2MASS). We find 2778 proper motion candidates, 647 of which are notlisted in SIMBAD. After comparison to Digitized Sky Survey images, wefind that 107 of our proper motion candidates lack counterparts at B, R,and I bands and are thus 2MASS-only detections. We present results ofspectroscopic follow-up of 188 targets that include the infrared-onlysources along with selected optical-counterpart sources with faintreduced proper motions or interesting colors. We also establish a set ofnear-infrared spectroscopic standards with which to anchor near-infraredclassifications for our objects. Among the discoveries are six youngfield brown dwarfs, five "red L" dwarfs, three L-type subdwarfs, twelveM-type subdwarfs, eight "blue L" dwarfs, and several T dwarfs. Wefurther refine the definitions of these exotic classes to aid futureidentification of similar objects. We examine their kinematics and findthat both the "blue L" and "red L" dwarfs appear to be drawn from arelatively old population. This survey provides a glimpse of the kindsof research that will be possible through time-domain infrared projectssuch as the UKIDSS Large Area Survey, various VISTA surveys, and WISE,and also through z- or y-band enabled, multi-epoch surveys such asPan-STARRS and LSST.Some of the spectroscopic data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership amongthe California Institute of Technology, the University of California,and the National Aeronautics and Space Administration. The Observatorywas made possible by the generous financial support of the W. M. KeckFoundation. Other spectroscopic data were collected at the SubaruTelescope, which is operated by the National Astronomical Observatory ofJapan.
| The effect of activity on stellar temperatures and radii
Context: Recent analyses of low-mass eclipsing binary stars haveunveiled a significant disagreement between the observations andpredictions of stellar structure models. Results show that theoreticalmodels underestimate the radii and overestimate the effectivetemperatures of low-mass stars but yield luminosities that accord withobservations. A hypothesis based upon the effects of stellar activitywas put forward to explain the discrepancies. Aims: In this paper westudy the existence of the same trend in single active stars and providea consistent scenario to explain systematic differences between activeand inactive stars in the H-R diagram reported earlier. Methods: Theanalysis is done using single field stars of spectral types late-K and Mand computing their bolometric magnitudes and temperatures throughinfrared colours and spectral indices. The properties of the stars insamples of active and inactive stars are compared statistically toreveal systematic differences. Results: After accounting for a numberof possible bias effects, active stars are shown to be cooler thaninactive stars of similar luminosity therefore implying a larger radiusas well, in proportions that are in excellent agreement with those foundfrom eclipsing binaries. Conclusions: The present results generalisethe existence of strong radius and temperature dependences on stellaractivity to the entire population of low-mass stars, regardless of theirmembership in close binary systems.Tables 1 and 2 are 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/478/507
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Exploring the Frequency of Close-in Jovian Planets around M Dwarfs
We discuss our high-precision radial velocity results of a sample of 90M dwarfs observed with the Hobby-Eberly Telescope and the Harlan J.Smith 2.7 m Telescope at McDonald Observatory, as well as the ESO VLTand the Keck I telescopes, within the context of the overall frequencyof Jupiter-mass planetary companions to main-sequence stars. None of thestars in our sample show variability indicative of a giant planet in ashort-period orbit, with a<=1 AU. We estimate an upper limit of thefrequency f of close-in Jovian planets around M dwarfs as <1.27% (atthe 1 σ confidence level). Furthermore, we determine that theefficiency of our survey in noticing planets in circular orbits is 98%for companions with msini>3.8MJ and a<=0.7 AU. Foreccentric orbits (e=0.6) the survey completeness is 95% for all planetswith msini>3.5MJ and a<=0.7 AU. Our results pointtoward a generally lower frequency of close-in Jovian planets for Mdwarfs as compared to FGK-type stars. This is an important piece ofinformation for our understanding of the process of planet formation asa function of stellar mass.Based on data collected with the Hobby-Eberly Telescope, which isoperated by McDonald Observatory on behalf of the University of Texas atAustin, Pennsylvania State University, Stanford University,Ludwig-Maximilians-Universität München, andGeorg-August-Universität Göttingen. Also based on observationscollected at the European Southern Observatory, Chile (ESO programs65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415, 69.C-0722, 70.C-0044,71.C-0498, 072.C-0495, 173.C-0606). Additional data were obtained at theW. M. Keck Observatory, which is operated as a scientific partnershipamong the California Institute of Technology, the University ofCalifornia, and the National Aeronautics and Space Administration(NASA), and with the McDonald Observatory Harlan J. Smith 2.7 mtelescope.
| 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.
| High Proper Motion Stars. IV. Radial Velocities of 166 Luyten Half-Second Stars
We present 178 radial velocity measurements for 166 late-type starsselected from the Luyten half-second (LHS) proper motion catalog. Spacevelocities are given for all but two of them. Most of the stars liewithin 25 pc of the Sun, but the list includes a handful ofhigh-velocity transients from the halo population. None of the derivedspace velocities is high enough, however, to provide any constraint onthe escape speed at the solar circle. Twenty-six stars are discussed insomewhat more detail, and evidence is adduced that several of them maybe velocity variables.
| Meeting the Cool Neighbors. VIII. A Preliminary 20 Parsec Census from the NLTT Catalogue
Continuing our census of late-type dwarfs in the solar neighborhood, wepresent BVRI photometry and optical spectroscopy of 800 mid-type Mdwarfs drawn from the NLTT proper-motion catalog. The targets are takenboth from our own cross-referencing of the NLTT Catalogue and the 2MASSSecond Incremental Data Release, and from the revised NLTT compiledrecently by Salim & Gould. All are identified as nearby-starcandidates based on their location in the(mr,mr-Ks) diagram. Three hundred starsdiscussed here have previous astrometric, photometric, or spectroscopicobservations. We present new BVRI photometry for 101 stars, togetherwith low-resolution spectroscopy of a further 400 dwarfs. In total, wefind that 241 stars are within 20 pc of the Sun, while a further 70 liewithin 1 σ of our distance limit. Combining the present resultswith previous analyses, we have quantitative observations for 1910 ofthe 1913 candidates in our NLTT nearby-star samples. Eight hundredfifteen of those stars have distance estimates of 20 pc or less,including 312 additions to the local census. With our NLTT follow-upobservations essentially complete, we have searched the literature for Kand early-type M dwarfs within the sampling volume covered by the 2MASSsecond release. Comparing the resultant 20 pc census against predictednumbers, derived from the 8 pc luminosity function, shows an overalldeficit of ~20% for stellar systems and ~35% for individual stars.Almost all are likely to be fainter than MJ=7, and at leasthalf are probably as yet undiscovered companions of known nearby stars.Our results suggest that there are relatively few missing systems at thelowest luminosities, MJ>8.5. We discuss possible means ofidentifying the missing stars.
| 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.
| 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
| Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog
We present refined coordinates and proper-motion data for the highproper-motion (HPM) stars in the Luyten Half-Second (LHS) catalog. Thepositional uncertainty in the original Luyten catalog is typicallygreater than 10" and is often greater than 30". We have used the digitalscans of the POSS I and POSS II plates to derive more accurate positionsand proper motions of the objects. Out of the 4470 candidates in the LHScatalog, 4323 objects were manually reidentified in the POSS I and POSSII scans. A small fraction of the stars were not found because of thelack of finder charts and digitized POSS II scans. The uncertainties inthe revised positions are typically ~2" but can be as high as ~8" in afew cases, which is a large improvement over the original data.Cross-correlation with the Tycho-2 and Hipparcos catalogs yielded 819candidates (with mR<~12). For these brighter sources, theposition and proper-motion data were replaced with the more accurateTycho-2/Hipparcos data. In total, we have revised proper-motionmeasurements and coordinates for 4040 stars and revised coordinates for4330 stars. The electronic version of the paper5 contains the updated information on all 4470stars in the LHS catalog.
| The Palomar/MSU Nearby Star Spectroscopic Survey. III. Chromospheric Activity, M Dwarf Ages, and the Local Star Formation History
We present high-resolution echelle spectroscopy of 676 nearby M dwarfs.Our measurements include radial velocities, equivalent widths ofimportant chromospheric emission lines, and rotational velocities forrapidly rotating stars. We identify several distinct groups by theirHα properties and investigate variations in chromospheric activityamong early (M0-M2.5) and mid (M3-M6) dwarfs. Using a volume-limitedsample together with a relationship between age and chromosphericactivity, we show that the rate of star formation in the immediate solarneighborhood has been relatively constant over the last 4 Gyr. Inparticular, our results are inconsistent with recent large bursts ofstar formation. We use the correlation between Hα activity and ageas a function of color to set constraints on the properties of L and Tdwarf secondary components in binary systems. We also identify a numberof interesting stars, including rapid rotators, radial velocityvariables, and spectroscopic binaries. Observations were made at the 60inch telescope at Palomar Mountain, which is jointly owned by theCalifornia Institute of Technology and the Carnegie Institution ofWashington.
| 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 Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2799H&db_key=AST
| Photometry of Stars with Large Proper Motion
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2300W&db_key=AST
| The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The Northern M Dwarfs -Bandstrengths and Kinematics
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.1838R&db_key=AST
| The general catalogue of trigonometric [stellar] paralaxes
Not Available
| The importance of surface inhomogeneities for K and M dwarf chromospheric fluxes
We present published and archived spectroscopic and spectrophotometricdata of H-alpha, Ca II, Mg II, and X-rays for a large sample of K and Mdwarfs. The data set points to the importance that surfaceinhomogeneities have in the flux luminosity diagrams in these late-typedwarfs, irrespective of whether the Balmer lines are in emission orabsorption. Although supporting the fact that cooler stars exhibitincreasing levels of surface activity, evident through an increasingincidence of Balmer emission, surface inhomogeneities, or variations inthe local temperature and density structure, at the chromospheric level,dominate the total Ca II and Mg II fluxes. We show that the flux-fluxand luminosity-luminosity relations indicate differing extents ofinhomogeneity from the chromosphere through to the corona. A goodcorrelation between Ca II and Mg II fluxes indicates that they areformed in overlapping regions of the chromosphere, so that thecontribution of surface inhomogeneities is not evident from thisparticular flux-flux diagram. In the region of the upper chromospherethrough to the transition and corona, the correlation between Ly-alphaand X-ray fluxes indicates regions with similar levels of arealinhomogeneity. This appears to be uncorrelated with that at thechromospheric level.
| A photometric study of K and M dwarf stars found by Stephenson
Broadband photometry has been obtained for a sample of the K and M dwarfstars found in an objective prism survey by Stephenson (1986). Among thestars with unknown proper motion, about 24 percent of those observedappear from the photometry not to be dwarfs, although the percentagevaries considerably with spectral type. For stars with V less than 11.5and B - V equal to or greater than 1.2, it is estimated that, within thearea surveyed, Stephenson's survey is about 68 percent complete.
| Chromospheric activity, kinematics, and metallicities of nearby M dwarfs
Attention is given to the results of more than 1000 observations ofabout 200 Gliese (1969) catalog M dwarfs, whose BVRIJHK photometry isbelieved to be accurate to 0.015 mag in each bandpass. An analysis ofthese data indicates that the H-alpha equivalent widths are a usefulchromospheric indicator for M dwarfs; as the chromosphere increases instrength, the H-alpha absorption equivalent width first increases, thendecreases, and H-alpha finally goes into emission, as predicted by Gramand Mullan (1979) for M dwarf chromospheres. The present JHK photometryis used to identify stars with metallicities that are significantlydifferent from that of the sun. It is noted that dMe stars in thissample generally have young disk motions, are more luminous than dMstars of the same color, and have B-V colors that are too blue for theirV-I color.
| Dwarf K and M stars of high proper motion found in a hemispheric survey
A recently completed visual/red spectral region objective-prism surveyof more than half the sky found some 2200 dwarf K and M stars ofnegligible proper motion (Stephenson, 1986). The present paper adds the1800-odd spectroscopically identified dwarfs that did prove to havesignificant proper motions. About half of these had previous spectralclassifications of some sort, especially by Vyssotsky (1952, 1956). Forthe great majority, the present coordinates are more accurate thanprevious data. The paper includes about 50 stars with unpublishedparallaxes, likely to have parallaxes of 0.05 arcsec or more. Combiningthe present data with the first paper suggests that the number oflow-proper-motion stars in that paper was not unreasonable.
| New subdwarfs. IV - UBV photometry of 1690 high-proper-motion stars
A photometric list of 1690 stars of known high proper motion is used tosearch for potential high-velocity stars of various metallicity valuesin order to find candidates for trigonometric programs on subdwarfs andto enlarge the sample with which to study the relation between stellarkinematics and metal abundance. A list of 113 stars with tangentialspace velocities of 300 km/s or greater is obtained, the highesttangential velocity relative to the sun being 630 km/s. By using thevariation of the tangential velocity with longitude and adopting thegalactic rotation at the solar circle to be 220 km/s, the rotation ofthe subdwarf system is estimated at 0 + or - 50 km/s from the transversevelocity alone, in agreement with determinations based on other methods.
| G. P. Kuiper's spectral classifications of proper-motion stars
Spectral classifications are listed for over 3200 stars, mainly of largeproper motion, observed and classified by Kuiper during the years1937-1944 at the Yerkes and McDonald Observatories. While Kuiper himselfpublished many of his types, and while improved classifications are nowavailable for many of these stars, much of value remains. For many ofthe objects, no other spectral data exist.
| Predicted infrared brightness of stars within 25 parsecs of the sun
Procedures are given for transforming selected optical data intoinfrared flux densities or irradiances. The results provide R, T(eff)blackbody approximations for about 2000 of the stars in Woolley et al.'sCatalog of Stars (1970) within 25 pc of the sun, and additional whitedwarfs, with infrared flux densities predicted for them at ninewavelengths from 2.2 to 101 microns including the Infrared AstronomySatellite bands.
| Erratum - Errors or Omissions in Star-Identifications in the General Catalogue of Trigonometric Stellar Parallaxes
Not Available
| Lowell proper motions II : proper motion survey of the Northern Hemisphere with the 13-inch photographic telescope of the Lowell Observatory
Not Available
| New proper-motion stars, (fifth list)
Not Available
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Perseo |
| Ascensione retta: | 04h08m37.40s |
| Declinazione: | +33°38'13.3" |
| Magnitudine apparente: | 10.219 |
| Distanza: | 13.697 parsec |
| Moto proprio RA: | 525.3 |
| Moto proprio Dec: | 126.9 |
| B-T magnitude: | 12.43 |
| V-T magnitude: | 10.402 |
Cataloghi e designazioni:
|
INHABITED SKY
