Spitzer Far-Infrared Detections of Cold Circumstellar Disks
Observations at 70 μm with the Spitzer Space Telescope have detectedseveral stellar systems within 65 pc of the Sun. Of 18 presumably youngsystems detected in this study, as many as 15 have 70 μm emission inexcess of that expected from their stellar photospheres. Five of thesystems with excesses are members of the Tucanae association. The 70μm excesses range from a factor of ~2 to nearly 30 times the expectedphotospheric emission from these stars. In contrast to the 70 μmproperties of these systems, there is evidence for an emission excess at24 μm for only HD 3003, confirming previous results for this star.The lack of a strong 24 μm excess in most of these systems suggeststhat the circumstellar dust producing the IR excesses is relatively cool(Tdust<~150 K) and that there is little IR-emittingmaterial within the inner few AU of the primary stars. Many of thesesystems lie close enough to Earth that the distribution of the dustproducing the IR excesses might be imaged in scattered light at opticaland near-IR wavelengths.
|
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. 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.
|
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
|
Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
|
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
|
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
|
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.
|
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 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.
|
Chromospheric heating in late-type dwarfs - Acoustic or magnetic?
Mg II h and k fluxes for 69 K and 88 M dwarfs have been analyzed. Anempirical lower limit is found in the Mg II flux, extended down to thelatest spectral types. Based on the data presented here it is themagnetic component that dominates the emission from the atmosphere ofcool dwarfs, especially the M dwarfs. It, however, coexists with anacoustically heated component, which can only be identified in the starswith the lowest fluxes in the flux-color diagram, these stars possiblybeing the slowest rotators. Data for the dM(e) stars, i.e., those starswith zero H-alpha, show that these are divided into two classes: (1) aninactive M dwarf star with very weak chromospheric heating, perhaps onlyby acoustic waves; and (2) an intermediate chromospheric activity stardominated by magnetic heating.
|
Kinematics of chromospherically active late-type dwarfs in the solar neighborhood
The space motions of chromospherically active late-type dwarfs(solar-type stars, K and M dwarfs, and BY Draconis binaries) areillustrated and discussed. Except for a small number of deviant stars,all the active single stars have the kinematics of young stars (ageabout 0.5 Gyr). The most egregious exception is HD 152391, which appearsto be a single star with a high level of chromospheric activity but withthe kinematics of the old disk population, for reasons unknown. The BYDra binaries, with a few exceptions, also have the kinematics of youth,being characterized by an age of about 1-2 Gyr. This lack of old BY Drabinaries seems puzzling, since a binary should be able to draw onorbital angular momentum to maintain rapid rotation well into old age,but this dearth is suggested to be due to the very rapid loss of angularmomentum that a double star can maintain until essentially all theangular momentum is lost and the stars coalesce. No strong kinematiccoherence is seen among the active single stars, indicating that thesestars were born in many different nurseries and have come to the solarneighborhood through random processes.
|
A study of excess H-alpha emission in chromospherically active M dwarf
Spectroscopic observations from three observatories are combined tostudy the properties of the excess H-alpha emission which characterizesthe most chromospherically active subset of the M dwarf stars, known asthe dMe stars. It is demonstrated that the excess H-alpha luminosityfrom these stars is a monotonically decreasing function of their (R-I)color, and evidence is presented which suggests that the product of themean surface brightness and the mean filling factor of the emissiveregions is essentially constant with color. Another significant resultof the study is a linear correlation between the excess luminosity inH-alpha and the coronal X-ray luminosity.
|
Radial-velocity measures and the existence of astrophysical binaries in late-type dwarf stars
Radial velocities with errors of 1-2 km/s are presented based on CCDscans obtained with the Kitt Peak National Observatory coude feedtelescope between 1982 and 1985 of 48 dK-M stars that lack Balmeremission. Comparison with Gliese's (1969) values shows only two stars tobe spectroscopic binary candidates with small velocity amplitudes. Noevidence for any short period (less than 10 days) binaries is found,supporting the conclusions of Young et al. (1986) that there are noastrophysical binaries among these chromosherically inactive dM stars.
|
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.
|
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.
|
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.
|
Catalogue of stars with CaII H and K emissions
Not Available
|
Variabilite D'etoiles Naines Rouges
Not Available
|
Etoiles Naines Rouges Variables
Not Available
|
Micrometric Measures of Double Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28..413V&db_key=AST
|
Spectral Types of M Dwarf Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28....1J&db_key=AST
|
The luminosity law for late-type main-sequence stars in the solar neighborhood
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..697E&db_key=AST
|
Calcium emission intensities as indicators of stellar age.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970MNRAS.148..463W&db_key=AST
|
Radial velocities of dK and dM stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967AJ.....72..905W&db_key=AST
|
Catalogue de 240 couples visuels d'étoiles naines rouges
Not Available
|
Preliminary list of radial velocities for 33 stars nearer than 20 parsecs
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960MNRAS.120..317L&db_key=AST
|
Mesures d'étoiles doubles faites au réfracteur de 38 cm de l'Observatoire de Nice
Not Available
|
Trigonometric parallaxes determined by photography with the McCormick 26-inch refractor.
Not Available
|
Photovisual magnitudes of 418 dwarf M stars and 34 parallax stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..219S&db_key=AST
|
INHABITED SKY
