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
|
Variability of Southern T Tauri Stars (VASTT). III. The Continuum Flux Changes of the TW Hydrae Bright Spot
We have collected low-resolution spectrophotometric data of theclassical T Tauri star TW Hya in an effort to detect and to follow theexcess continuum emission (veiling) and the line changes atλ<5100 Å. The deveiled and calibrated flux distributionresembles that of a 30 Myr K7-M1 star of radius R=0.8Rsolar,mass M=0.7Msolar, and logg=4.5. The anticorrelation betweenthe veiling (in the B band) and the observed Balmer jump found byprevious authors, based on large samples of classical T Tauri stars, isconfirmed in TW Hya. The line emission luminosities of the H, Ca II, andHe I lines correlate with one another throughout the series, supportingthe claims that the bulk of the line emission is formed in a singleregion or that their growth is controlled by a common mechanism.Surprisingly, the line emission fluxes do not correlate with the veilingat 4250 Å (B band). The line luminosities are, in general, lessthan 1% of the continuum luminosities. The veiling time series presentsa cyclic behavior at 4.4+/-0.4 days. We collect all of the archivalphotometric data and analyze the B-band observations using differentalgorithms. We found solutions at either the 4.4 day timescale orone-half of this value. The data sets presenting the 2.2 day periodicityyield double-peaked light curves when folded at the 4.4 day timescale.We interpret the 4.4 day solution as the rotation period of the star.The veiling and the line emission measurements yield accretionluminosities for the series. We model the impacted area in thephotosphere by an isothermal gas of a given density, temperature, andsize (δ) whose parameters change as the star rotates. Estimates ofthe total spot area (δ), as a percentage of the stellar projectedarea, lie within the range 2.5<δ<6.0. The accretionluminosity of the impacted region does not remain constant throughoutthe series. The mass accretion rate (Macc) that governs theluminosity varies within1.0×10-9Msolaryr-1
|
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.
|
Variability of Southern T Tauri Stars. II. The Spectral Variability of the Classical T Tauri Star TW Hydrae
We present the analysis of 42 spectra of the Classical T Tauri star TWHya observed with the FEROS echelle spectrograph over 2 yr. Wedetermined the rotational and radial velocities of TW Hya, obtainingvsini=5+/-2 km s-1 and vrad=12.5+/-0.5 kms-1. The star exhibits strong emission lines that showsubstantial variety and variability in their profile shapes. Emissionlines such as Hα, Hβ, and He I show both outflow and infallsignatures, which change on different timescales. The system displaysperiodic variations in line and veiling intensities, but the stellarrotation period remains uncertain. We see evidence of a variation in themass accretion rate over a 1 yr period from the Na D line profiles thatare well fitted by magnetospheric accretion models with moderate massaccretion rates (10-9 up to 10-8 Msolaryr-1). The lower values inferred from the models are close tothe average mass accretion rate obtained from the veiling estimates(~2×10-9 Msolar yr-1), but theveiling results are consistent with a constant mass accretion ratewithin the errors of the calculations. The Hα, He I, Na D, andHβ emission-line equivalent widths corrected from veiling correlatewell with each other and are correlated with the veiling, indicating thesame mechanism should be powering them and suggesting an origin relatedto the accretion process. The wings of the main emission lines aregenerally correlated, except when the Balmer lines exhibit propertiessuggesting a strong contribution from a wind. The blueward absorptioncomponents of the Balmer lines, most likely from a wind, are notcorrelated with veiling. The spectroscopic analysis allows us to inferthe inclination of the stellar rotation axis(i=18deg+/-10deg) that matches the currentestimations of the disk orientation(0deg
|
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
|
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.
|
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.
|
Some Cross-Reference Lists for the Catalog of Possible Nearby Stars
Not Available
|
Catalogue of stars with CaII H and K emissions
Not Available
|
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.
|
Nearby Star Data Published 1969-1978
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979A&AS...38..423G&db_key=AST
|
Spectral types for proper motion stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80..239B&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
|
Lowell proper motions III : proper motion survey of the Northern Hemisphere with the 13-inch photographic telescope of the Lowell Observatory
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
|
The radial velocities of 166 red dwarf stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954AJ.....59..218D&db_key=AST
|
Dwarf M Stars Found Spectrophotometrically.
Abstract image available at:http://adsabs.harvard.edu/abs/1943ApJ....97..381V
|
