|Spectroscopy of the open cluster Blanco 1 II. H alpha emission as an indicator of relative age|
We present the results of H alpha (6562\AA) and Li i (6708\AA)observations of 114 low-mass stars of the young open cluster Blanco 1.We also present observations of 30 stars in Ca ii(K). This work extendsthe first Blanco 1 spectroscopic study of Panagi et al. (1994). From asample of four well-studied clusters, including Blanco 1, we find thatthe fraction of H alpha emission-line stars amongst K dwarfs is a goodindicator of relative age, with a smaller fraction indicative of olderage. Blanco 1 shows a relatively small fraction of emitters,inconsistent with previous age estimates for the cluster. We estimatethe cluster age to to be 90 +/- 25 Myr, slightly older than thePleiades. The method is shown to be more sensitive to age than lithiumand a useful alternative to other age measurement techniques. Thevariation of H alpha with (B-V) is similar to that observed in the oldersolar neighbourhood dwarfs, suggesting that, at least for theabsorption-line stars, the contribution of stellar rotation to theequivalent width is unclear. We combine both spectroscopy and photometryto revise cluster membership and give accurate positions for all thesestars. Tables A1 and A2 are available at the CDS via anonymous ftp126.96.36.199 or http://cdsweb.u-strabg.fr./Abstract.html
|A catalog of K giants at the South Galactic Pole - Broadband and DDO photometry and radial velocities|
We describe a sample of K giants at the South Galactic Pole, selected toexamine the chemical and kinematical properties of stars perpendicularto the galactic plane and to measure the local column density of thedisk. We report velocities, abundances, absolute magnitudes, andbroadband BV photometry for over 500 giants.
|Local dark matter from a carefully selected sample|
The precise data obtained by Flynn and Freeman (1991) on K giants at thesouth Galactic pole are used to analyze the amount of local dark matterin which the systematic effects can be modeled easily and evaluatedaccurately. The method of Bahcall (1984) is employed to solve theself-consistent equations for the distribution of dark matter. TheK-giant survey is found to provide significant evidence for disk darkmatter. Taking into account all recognized sources of error using astatistical test devised by Gould (1989, 1990), a model with no darkmatter is inconsistent with the data at the 86-percent confidence level.The best-fit P-model (in which dark matter is distributed proportionallyto known matter) has 53 percent more dark matter than visible matter.
|UBV and uvby-beta photometry of stars in the region of the Zeta SCULPTORIS cluster|
Photoelectric observations of 130 stars in the region of Zeta Sculptorishave been obtained in UBV and uvby-beta. A total of 32 stars areidentified as cluster members, and several other F and G type stars areidentified as probable members. Results indicate an interstellarreddening of E(B-V) = 0.02 mag and that the cluster is slightly metaldeficient.
|Photometric study of Zeta SCULPTORIS cluster|
Photographic photometry of about 1500 stars in the region of the ZetaSculptoris cluster has been accomplished, and relations between thisphotometry and broad- and intermediate-band photoelectric photometryestablished. From observation of the H-R diagrams, it is concluded thatabout 150 stars belong to the unevolved main sequence of the cluster. Asmall reddening of E(B - V) = 0.013 m similar to values given by otherauthors, and a mean modulus of about 6.9 mag, have been determined. Twogaps exist in the main sequence, one between (B - V) about 0.06 m andabout 0.30 m and the other around (B - V) about 1.00.
|The common origin of some open clusters|
Eight open clusters have been observed with uvby-beta photometry and forseven of them the metal abundances have been determined. Six of thesehave similar metallicities. They are close in space and are also knownto have similar ages and radial velocities. These clusters are suspectedof having a common origin. Some studies are made of the reliability ofthe photometric system. A large gain in limiting magnitude can beachieved against an unimportant loss of accuracy if interference filtersare removed.
|Spectral types in the Zeta SCULPTORIS open cluster|
The spectral types of 20 stars in the Blanco 1 open cluster (ZetaSculptoris) are reported. Spectral classification in the MK system wasperformed on the basis of 125-A/mm dispersion spectra obtained with a0.9-m telescope and a Cassegrain spectrograph. Of the stars classified,one classical Am star, one peculiar star with a weak K-line and one Apstar with marginal Si II lines enhancement were found, while the starZeta Scl itself is observed to be a main sequence object and thusprobably a foreground star. An H-R diagram of the cluster is alsopresented, and other probable members and nonmembers are indicated.
|Multicolor photometry of the ZET Scl open cluster.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90...81P&db_key=AST
|Cyanogen Strengths, Luminosities, and Kinematics of K Giant Stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975ApJS...29..161J&db_key=AST
|Four-color photoelectric photometry of two high-latitude clusters.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..556E&db_key=AST