A photometric pilot study on Sonneberg archival patrol plates. How many ``constant'' stars are in fact long-term variables?
The light curves of 216 arbitrarly chosen field stars and of 23 knownvariables in the Aur/Tau/Ori region were derived (7.8 m ≤ B ≤12.2 m) from scanned, blue-sensitive archival patrol plates, covering atotal of 34 years (1961-1995). We achieved a photometric accuracy of0.07 ... 0.12 mag in spite of rather unfavourable locations of moststars near the plate borders. 17 field stars turned out to be variables,most of them with time scales of 1000-8000 days in the form of slowwaves with amplitudes between 0.1 and 0.3 mag, i.e. below the thresholdof traditional variable searches on photographic plates. About 50% ofthese new long-term variables exhibit drifts indicating periodic orerratic variability at much longer time scales than covered here. Forthe 23 known variables we achieved improvements in their periods andamplitudes and detected long-term variations (drifts, waves) in about50% of them. The above fraction of low-amplitude long-term variablesamong field stars implies that a total of about 45 000 new variablesshould be detectable in the Sonneberg patrol plate archive. They willrepresent a new, hitherto not investigated population of variable starswith a possibly significant impact on our understanding of the stellarinterior and evolution.Tables 2 and 3 are only available in electronic form athttp://www.edpsciences.org
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Kinematics of Metal-poor Stars in the Galaxy. II. Proper Motions for a Large Nonkinematically Selected Sample
We present a revised catalog of 2106 Galactic stars, selected withoutkinematic bias and with available radial velocities, distance estimates,and metal abundances in the range -4.0<=[Fe/H]<=0.0. This updateof the 1995 Beers & Sommer-Larsen catalog includes newly derivedhomogeneous photometric distance estimates, revised radial velocitiesfor a number of stars with recently obtained high-resolution spectra,and refined metallicities for stars originally identified in the HKobjective-prism survey (which account for nearly half of the catalog)based on a recent recalibration. A subset of 1258 stars in this cataloghave available proper motions based on measurements obtained with theHipparcos astrometry satellite or taken from the updated AstrographicCatalogue (second epoch positions from either the Hubble Space TelescopeGuide Star Catalog or the Tycho Catalogue), the Yale/San Juan SouthernProper Motion Catalog 2.0, and the Lick Northern Proper Motion Catalog.Our present catalog includes 388 RR Lyrae variables (182 of which arenewly added), 38 variables of other types, and 1680 nonvariables, withdistances in the range 0.1 to 40 kpc.
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The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
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Kinematics of metal-poor stars in the galaxy
We discuss the kinematic properties of a sample of 1936 Galactic stars,selected without kinematic bias, and with abundances (Fe/H) is less thanor equal to -0.6. The stars selected for this study all have measuredradial velocities, and the majority have abundances determined fromspectroscopic or narrow-/intermediate-band photometric techniques. Incontrast to previous examinations of the kinematics of the metal-poorstars in the Galaxy, our sample contains large numbers of stars that arelocated at distances in excess of 1 kpc from the Galactic plane. Thus, amuch clearer picture of the nature of the metal-deficient populations inthe Galaxy can now be drawn.
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The SVS Numbering Series Discontinued
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U, V, W velocity components for the old disk using radial velocities of 1295 stars in the three cardinal Galactic directions
New radial velocities are presented for 1295 stars chosen at random nearthe three cardinal Galactic directions of l = 180 deg, b = 0; l = 90deg, b = 0 deg; and b = 90 deg, giving the distribution in U, V, and W,respectively, from the radial velocities alone. The measurements weremade with the coude spectrograph of the Mount Wilson 100 in. Hookerreflector. The purpose of the program is to set limits on the densitynormalization in the solar neighborhood of the old thin disk, the oldthick disk, and the halo. Many more high-velocity stars are present inthe unbiased sample than expected from previous estimates of thenormalization. The data suggest the density ratios in the solarneighborhood to be about 90 percent, 10 percent, and about 0.5 percentfor the thin disk, thick disk, and halo populations, respectively.
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Visuelle und photovisuelle Beobachtungen von drei Verand.n.
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Photometric variations of Orion population stars. III - RY Tau, T Ori, NV Ori, and HH AUR
UBVRI and H-alpha photometry of four Orion population stars has beenobtained with the Perkin telescope at Van Vleck Observatory during theinterval of October 1983 to March 1984. RY Tau underwent a dramaticincrease in brightness during this period, reaching a level (V = 9.43)not seen in more than two decades. At the same time, the equivalentwidth of its H-alpha emission line (measured photometrically) decreasedand, in the longer-wavelength color indices, has begun to show the'bluer when brighter' syndrome characteristic of other weakemission-line Orion population stars. Spectra taken during the 1983-1984season, or as soon as possible this season (if the star remains bright),could provide critical information on the nature of the variabilitymechanism. T Ori and NV Ori also showed substantial variability, andtheir color and H-alpha characteristics are discussed. HH Aur showedlittle or no variation during the present observations.
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Photometry of T Tauri Stars and Related Objects at Van Vleck Observatory
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Photometric and Spectroscopic Monitoring of T-Tauri Stars and Related Objects at Van-Vleck Observatory
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Discussion of infrared measurements of T Tauri stars and related objects
It is pointed out that in comparison with main-sequence stars of thesame spectral type, all irregular variable stars in thepre-main-sequence stage (briefly called T Tauri stars), show an infraredexcess. Infrared observations provide information concerning thephysical characteristics of stars, including the total energy output.The reported investigation considers infrared observations of T Tauristars conducted during the last ten years. The exclusion of some starsnot belonging to the group of the T Tauri stars is considered along withaspects related to a subdivision of the T Tauri stars. The various typesof T Tauri stars with their characteristics are represented in graphs.It is found that in some cases the infrared excess may be caused by thethermal radiation of the circumstellar particles which are heated by thestar. In other stars, thermal bremsstrahlung and dust radiation areresponsible for the infrared excess.
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An infrared survey of RW Aurigae stars
An infrared photometric survey of 89 RW Aur type variables in bothhemispheres has been made. JHKL magnitudes and colors are listed. The RWAur variables include a small number of highly reddened late-type stars.All T Tauri and hot Orion population stars show infrared excesses andthe infrared properties mark certain field stars as being young. Thegreatest infrared excesses are found for A and F stars while youngvariable B stars usually show no excesses. The location of the RW Aurstars in the two-color H-K, K-L diagram favor dust re-radiation overfree-free emission as the mechanism responsible for the infrared excess.A weak correlation of H-K with emission class links the occurrence ofcircumstellar dust and gas shells.
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Infra-red observations of young stars - IV. Radiative mechanisms and interpretations.
Abstract image available at:http://adsabs.harvard.edu/abs/1973MNRAS.164..395C
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Infra-red observations of young stars. II. T Tau stars and the ORI population.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.161...97C&db_key=AST
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Photographic Proper Motions and the Mean Parallax of RW Aurigae Variables
Not Available
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Spectral Classifications for 112 Variable Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960ApJ...131..632H&db_key=AST
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Absolute Proper Motions of 21 Variables of the RW Aur Type.
Not Available
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Report of proceedings of Armagh Observatory
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On 3 recently discovered variables.
Not Available
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Bright Late M-Type Stars Near the Galactic Equator.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...120..118N&db_key=AST
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INHABITED SKY
