Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
Lithium Abundances in Wide Binaries with Solar-Type Twin Components
We present high-resolution spectroscopic observations of the Li Iresonance line in a sample of 62 stars that belong to 31 common propermotion pairs with twin F- or G-type components. Photospheric abundancesof lithium were derived by spectral synthesis analysis. For seven of thepairs, we have measured large lithium abundance differences. Elevenother pairs have components with similar lithium abundances. We cannotdetermine if the remaining 13 pairs have lithium differences because wedid not detect the Li I lines, and hence we can only provide upperlimits to the abundances of both stars. Our results demonstrate thattwin stars do not always share the same lithium abundances. Lithiumdepletion in solar-type stars does not only depend on age, mass, andmetallicity. This result is consistent with the spread in lithiumabundances among solar-type stars in the solar-age open cluster M67. Ourstars are brighter than the M67 members of similar spectral type, makingthem good targets for detailed follow-up studies that could shed lighton the elusive mechanism responsible for the depletion of lithium duringthe main-sequence evolution of the Sun and solar-type stars.
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| 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.
| Common proper motion stars in the AGK 3
A search was made of common-proper-motion (CPM) systems among AGK 3stars. The selection of physical systems was based upon the ratiobetween the angular separation (rho) and the proper motion (mu); the CPMstars found are presented in two tables. Table I lists systems withrho/mu less than 1000 years. It contains 326 entries, and the proportionof optical pairs is estimated to be 1 percent. Table II lists systemswith rho/mu in the range 1000 to 3500 years; it contains 113 systems,but only 60 percent of them are physical. Nevertheless, these systemsoften have separations larger than 10,000 AU and are the mostinteresting for the study of the tail of the distribution function ofthe semimajor axes.
| New double stars (10th series) discovered at Nice
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...12..137C&db_key=AST
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Arabaci |
| Sað Açýklýk: | 05h52m47.38s |
| Yükselim: | +29°46'13.3" |
| Görünürdeki Parlaklýk: | 9.116 |
| Uzaklýk: | 10000000 parsek |
| özdevim Sað Açýklýk: | 0 |
| özdevim Yükselim: | 0 |
| B-T magnitude: | 10.188 |
| V-T magnitude: | 9.205 |
Kataloglar ve belirtme:
|
