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Completeness of USNO-B for High Proper Motion Stars
I test the completeness of USNO-B detections of high proper motion(μ>180 mas yr-1) stars and the accuracy of itsmeasurements by comparing them to the revised New Luyten Two-Tenthscatalog of Salim & Gould. For 14.5~20 mas yr-1) may actuallyhave still larger errors than tabulated.
| 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.
| Candidate Pre-Main-Sequence F Stars with Circumstellar Dust Identified Using Combined 2MASS and uvby Data
We propose a method that uses near-infrared plus uvby photometry toidentify potentially extensive circumstellar dusty environments around Fand A stars. The method has been applied to a sample of ~900 metal-richreddened F stars with 2 Micron All Sky Survey and uvby data, suggestingthe presence of circumstellar dust emitting in the near-infrared for ~70stars. The logTe-MV diagram suggests that most, ifnot all, are likely pre-main-sequence (PMS) stars. They seem to be acontinuation of the class of Herbig Ae/Be PMS stars in the spectral typeF. Their number drops sharply downward of logTe~3.84(spectral types later than ~F5), which may provide new clues to the PMSevolution of 1-2 Msolar stars. We present a list of 21 of themost conspicuous candidate stars with circumstellar dust. About half ofthem are associated with the extended star-forming region around ρOphiuchi. The brightest of these 21 stars, with V<~7.5, turn out tobe IRAS sources, suggesting the presence of heated dust emitting in thefar-infrared. Also in this list, HD 81270 is reported as a very unusualstar moving away from the Galactic plane at a projected speed of 70 kms-1.
| Mining the Metal-rich Stars for Planets
We examine the correlation between stellar metallicity and the presenceof short-period planets. It appears that approximately 1% of dwarf starsin the solar neighborhood harbor short-period planets characterized bynear-circular orbits and orbital periods P<20 days. However, amongthe most metal-rich stars (defined as having [Fe/H]>0.2 dex), itappears that the fraction increases to 10%. Using the Hipparcos databaseand the Hauck & Mermilliod compilation of Strömgren uvbyphotometry, we identify a sample of 206 metal-rich stars of spectraltype K, G and F which have an enhanced probability of harboringshort-period planets. Many of these stars would be excellent candidatesfor addition to radial velocity surveys. We have searched the Hipparcosepoch photometry for transiting planets within our 206 star catalog. Wefind that the quality of the Hipparcos data is not high enough to permitunambiguous transit detections. It is, however, possible to identifycandidate transit periods. We then discuss various ramifications of thestellar metallicity-planet connection. First, we show that there ispreliminary evidence for increasing metallicity with increasing stellarmass among known planet-bearing stars. This trend can be explained by ascenario in which planet-bearing stars accrete an average of 30M⊕ of rocky material after the gaseous protoplanetarydisk phase has ended. We present dynamical calculations which suggestthat a survey of metallicities of spectroscopic binary stars can be usedto understand the root cause of the stellar metallicity-planetconnection.
| New proper motion determination of Luyten catalogue stars (LTT) with declination between -5(deg) and -30(deg) and right ascension between 0h and 13h 30m
Data are given for 353 LTT stars found on 42 areas, covering 25 squaredegrees each, with declination between -5(deg) and -30(deg) and rightascension between 0h and 13h 30m. Nineteen stars present differences inproper motion >= 0('') 10, twenty present differences in positionangle >= 20(deg) and six present those differences in both values.Table 2 only available in electronic foun at CDS viahttp://cdsweb.u-strasbg.fr/Abstract.html. Finding charts only availablein the electronic version.
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