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The young active star SAO 51891 (V383 Lacertae)
Aims: The aim of this work is to investigate the surface inhomogeneitiesof a young, late-type star, SAO 51891, at different atmospheric levels,from the photosphere to the upper chromosphere, analyzingcontemporaneous optical high-resolution spectra and broad-bandphotometry. Methods: The full spectral range of FOCES@CAHA (R≃ 40 000) is used to perform the spectral classification and todetermine the rotational and radial velocities. The lithium abundance ismeasured to obtain an age estimate. The {BVRIJHK}sphotometric bands are used to construct the spectral energy distribution(SED). The variations in the observed BV fluxes and effectivetemperature are used to infer the presence of photospheric spots andobserve their behavior over time. The chromospheric activity is studiedapplying the spectral subtraction technique to Hα, Ca ii H &K, Hɛ, and Ca ii IRT lines. Results: We find SAO 51891 tobe a young K0-1V star with a lithium abundance close to the Pleiadesupper envelope, confirming its youth ( 100 Myr), which is also inferredfrom its kinematical membership of the Local Association. No infraredexcess is detected from analysis of its SED, limiting the amount ofremaining circumstellar dust. We detect a rotational modulation of theluminosity, effective temperature, Ca ii H & K, Hɛ, and Caii IRT total fluxes. A simple spot model with two main active regions,about 240 K cooler than the surrounding photosphere, fits the observedlight and temperature curves very well. The small-amplitude radialvelocity variations are also well reproduced by our spot model. Theanti-correlation of light curves and chromospheric diagnostics indicateschromospheric plages spatially associated with the spots. The largestmodulation amplitude is observed for the Hɛ flux suggesting thatthis line is very sensitive to the presence of chromospheric plages. Conclusions: SAO 51891 is a young active star, lacking significantamounts of circumstellar dust or any evidence of low mass companions,and displays the typical phenomena produced by magnetic activity. Thespots are larger and warmer than those in less active main-sequencestars. If some debris is still present around the star, it will only bedetectable by future far-infrared and sub-mm observations (e.g.,Herschel or ALMA). The RV variation produced by the starspots has anamplitude comparable with those induced by Jupiter-mass planets orbitingclose to the host star. SAO 51891 is another good example of an activestar in which the detection of planets may be hampered by the highactivity level.Based on observations collected at Calar Alto Astronomical Observatory(Spain) and Catania Astrophysical Observatory (Italy).
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Photoelectric Vilnius Photometry of Hipparcos Turn-Off Region Stars
Seven-color photometry in the Vilnius system and photometricclassification in terms of spectral type, absolute magnitude andmetallicity are presented for 145 Hipparcos stars of the turn-offregion, most of which have parallaxes determined to an accuracy of atleast 15%. The stars selected for the observing program included thoseidentified kinematically as intermediate between the thin disk and halo,plus a number of weak-lined stars discovered previously from objectiveprism surveys. The metallicity distribution we find for a kinematicallydefined sample of possible members of the thick disk has a meanabundance [Fe/H]= --0.3 dex and a dispersion of 0.3 dex. Our data seemto suggest a large age for this intermediate population.
| Kinematics of Sandage-Fouts stars in three cardinal directions
V and (B - V) for 429, 442, and 427 stars are observed in the directionsof the anticenter, Cygnus, and the NGP, respectively, and DDO colors forthose stars G0 and later. The samples observed are ones for whichSandage and Fouts (1987) have published radial velocities. W, V, and Wcomponents of space velocity are derived from DDO distances withavailable proper motions. A clear correlation was found to exist betweenthe velocity dispersions and Fe/H with the dispersions decreasing asFe/H increases to about + 0.00, where V then becomes significantlynegative. The 'thick disk' component is clearly recognized, with sigma(W) approximately equal to 36 km/sec. In the 'old thin disk' and the'young thin disk', 43 percent and 42 percent of the stars have negativeV values, respectively.
| 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.
| New proper-motion stars, (second list)
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