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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.
| 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.
| A surprise at the bottom of the main sequence: Rapid rotation and NO H-alpha emission
We report Kech Observatory high-resolution echelle spectra from 640-850nm for eight stars near the faint end of the main sequence. Thesespectra are the highest resolution spectra of such late-type stars, andclearly resolve the TiO, VO, and atomic lines. The sample includes thefield brown-dwarf candidate, BRI 0021-0214 (M9.5+). Very unexpectedly,it shows the most rapid rotation in the entire samples, v sin iapproximately 40 km/s, which is 20x faster than typical fieldnonemission M stars. Equally surprising is that BRI 0021 exhibits noemission or absorptionat H-alpha. We argue that this absence is notsimply due to its cool photosphere, but that stellar activity declinesin a fundamental way at the end of the main sequence. As it is the firstvery late M dwarf observed at high spectral resolution, BRI 0021 may besignaling a qualitative change in the angular momentum loss rate amongthe lowest mass stars. Conventionally, its rapid rotation would havemarked BRI 0021 as very young, consistent with the selection effectwhich arises if the latest-type dwarfs are really brown dwarfs oncooling curves. In any case, it is unprecedented to find no sign ofstellar activity in such a rapidly rotating convective star. We alsodiscuss the possible conflict between this observation and the extremelystrong H-alpha seen in another very cool star, PC 0025+0447.Extrapolation of M-L relations for BRI 0021 yields M approximately 0.065solar mass, and the other sample objects have expected masses near theH-burning limit. These include two Pleiades brown-dwarf candidates, fourfield M6 dwarfs and one late-type T Tauri star. The two Pleiades M6dwarfs have v sin i of 26 and 37 km/s, H-alpha in emission, and radialvelocities consistent with Pleiades M6 dwarfs have v sin i of 26 and 37km/s, H-alpha in emission, and radial velocities consistent withPleiades membership. Similarly, the late-type T Tauri star has v sin iapproximately 30 km/s and H alpha emission indicate of its youth. Two ofthe four late-type field dMe star also exhibit rotation above 5 km/s,consistent with expectations. BRI 0021 has no measurable absoprtion dueto lithium, indicating that it is likely to be more massive than 0.065solar mass.
| Photometric parallaxes for selected stars of color class M from the NLTT catalog. II - The declination zone 0 deg to +20 deg
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986AJ.....91..626W&db_key=AST
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| Takýmyýldýz: | Baliklar |
| Sað Açýklýk: | 00h38m50.99s |
| Yükselim: | +03°42'18.1" |
| Görünürdeki Parlaklýk: | 11.972 |
| özdevim Sað Açýklýk: | 207.2 |
| özdevim Yükselim: | 84.8 |
| B-T magnitude: | 12.959 |
| V-T magnitude: | 12.054 |
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