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Investigation of the Pleiades cluster. III. Additional corona members.
The analysis of CORAVEL radial velocities of 93 stars selected on thebasis of their proper motion and Geneva CCD photometric observations for57 stars have permitted to identify 25 new members in the outer part ofthe Pleiades. Several spectroscopic binaries have been discovered, buttheir membership is not clear. Two orbits with short periods have beendetermined, but both stars are probably non-members. The total number ofmember stars in the outer part of the Pleiades in the spectral rangeF5-K0 (0.45 < B-V < 0.90) is now 81 which is comparable to thenumber of stars known in Hertzsprung's central area (88 stars) in thesame spectral domain. Therefore at least 48 % of the F5-K0 main-sequencestars are located in the outer part of the cluster. And the census isprobably still incomplete.
| Membership probabilities in the Pleiades field.
A catalogue of proper motions and photographic B, V magnitudes for starsup to B=19mag within a region centered near Alcyone is presented. Thecatalogue is based on MAMA measurements of 8 plates taken with theTautenburg Schmidt telescope. The survey includes ca. 14500 stars andcovers a total field of about 9 square degrees. For stars brighter thanB=18mag an internal accuracy of 0.05mag and 2.5mas/year has beenestimated for photometric data and proper motions, respectively.Membership probabilities, proper motions and B, V magnitudes are listedfor 442 stars up to B=19mag in the Pleiades field.
| Rotation and chromospheric emission among F, G, and K dwarfs of the Pleiades
High-resolution echelle spectra of more than 100 F, G, and K dwarfs inthe Pleiades are reported. Chromospheric activity in these stars ismeasured via comparisons of the profiles of H-alpha and the Ca II IRtriplet to chromospherically inactive field stars. Consistent dereddenedcolors are determined from the available photometry and temperatures arederived. Most G and K dwarfs in the Pleiades rotate slowly, but about 20percent of the stars are ultrafast rotators (UFRs). That fraction ofUFRs is independent of color, and the highest rotation rates are foundamong the K dwarfs. The Pleiades exhibit a broad range in the strengthof chromospheric emission at any one color. Most G and K dwarfs in thePleiades show H-alpha and the IR triple in absorption, with filling inof the line cores.
| The search for faint members of the Pleiades. I - A proper motion membership study of the Pleiades to M(V) of about 12.5
New probable Pleiades cluster members are identified, based on anunbiased survey of stars within 4 x 4-deg region centered near Alcyone.The faint magnitude limit of the survey is about V = 18, and the brightlimit is about V = 14. In order to accurately define the luminosityfunction of the Pleiades, new proper motions are derived for a largenumber of stars previously suggested as possible Pleiades members.Accurate coordinates, V magnitudes, and membership probabilities areprovided for these stars.
| A VBLUW photometric survey of the Pleiades cluster
Photometric data are presented for 390 known or suspected members of thePleiades cluster. The data were obtained in 1979 at ESO using theWalraven VBLUW photometer and the Dutch 91-cm telescope. A comparisonwas made with subsets obtained with the same telescope andinstrumentation at the former Leiden Southern Station at the SAAO annexduring 1976 and 1977, and with data obtained at ESO during 1980 and1981. The much improved performance of the telescope and the photometerat their new site is obvious from these comparisons. The stars measuredcomprise the selection of possible members by Hertzsprung (1947)brighter than m(pg) = 14.5 and a selection of possible members in theouter region of the cluster by Pels et al. (1975). Of the starsselected, 66 were found not to be members. A few of these are possiblyescaping members. The present data set provides a well determined mainsequence over the range K2V to B9V, as well as data on some of theprobably premain-sequence K2-to-K5 and postmain-sequence B8-to-B6 stars.Finding charts for the stars selected by Pels are presented in anappendix.
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