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uvby? photometry of early type open cluster and field stars
Context. The ? Cephei stars and slowly pulsating B (SPB) stars aremassive main sequence variables. The strength of their pulsationaldriving strongly depends on the opacity of iron-group elements. As manyof those stars naturally occur in young open clusters, whosemetallicities can be determined in several fundamental ways, it islogical to study the incidence of pulsation in several young openclusters. Aims: To provide the foundation for such aninvestigation, Strömgren-Crawford uvby? photometry of opencluster target stars was carried out to determine effectivetemperatures, luminosities, and therefore cluster memberships. Methods: In the course of three observing runs, uvby? photometryfor 168 target stars was acquired and transformed into the standardsystem by measurements of 117 standard stars. The list of target starsalso included some known cluster and field ? Cephei stars, as wellas ? Cephei and SPB candidates that are targets of theasteroseismic part of the Kepler satellite mission. Results: Theuvby? photometric results are presented. The data are shown to beon the standard system, and the properties of the target stars arediscussed: 140 of these are indeed OB stars, a total of 101 targets liewithin the ? Cephei and/or SPB star instability strips, and eachinvestigated cluster contains such potential pulsators. Conclusions: These measurements will be taken advantage of in a numberof subsequent publications.Based on measurements obtained at McDonald Observatory of the Universityof Texas at Austin.Tables 3-6 are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/528/A148
| 2MASS 22344161+4041387AB: A Wide, Young, Accreting, Low-Mass Binary in the LkH?233 Group
We report the discovery of a young, 0farcs16 binary, 2M2234+4041AB,found as the result of a Keck laser guide star adaptive optics imagingsurvey of young field ultracool dwarfs. Spatially resolved near-infraredphotometry and spectroscopy indicate that the luminosity and temperatureratios of the system are near unity. From optical and near-infraredspectroscopy, we determine a composite spectral type of M6 for thesystem. Gravity-sensitive spectral features in the spectra of2M2234+4041AB are best matched to those of young objects (~1 Myr old). Acomparison of the T eff and age of 2M2234+4041AB toevolutionary models indicates that the mass of each component is0.10+0.075 -0.04 M sun. Emission linesof H? in the composite optical spectrum of the system andBr? in spatially resolved near-IR spectra of the two componentsindicate that the system is actively accreting. Both components of thesystem have IR excesses, indicating that they both harbor circumstellardisks. Though 2M2234+4041AB was originally identified as a young fielddwarf, it lies 1farcm5 from the well-studied Herbig Ae/Be star,LkH?233. The distance to LkH?233 is typically assumed to be880 pc. It is unlikely that 2M2234+4041AB could be this distant, as itwould then be more luminous than any known Taurus objects of similarspectral type. We re-evaluate the distance to the LkH?233 groupand find a value of 325+72 -50 pc, based on theHipparcos distance to a nearby B3-type group member (HD 213976).2M2234+4041AB is the first low-mass star to be potentially associatedwith the LkH?233 group. At a distance of 325 pc, its projectedphysical separation is 51 AU, making it one of the growing number ofwide, low-mass binaries found in young star-forming regions.Some of the data presented herein were obtained at the W. M. KeckObservatory, which is operated as a scientific partnership among theCalifornia Institute of Technology, the University of California, andthe National Aeronautics and Space Administration. The Observatory wasmade possible by the generous financial support of the W. M. KeckFoundation.
| Four-color photometry for the association Lac OB1.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88..930C&db_key=AST
| Spectral classification of stars in Lac OB1
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81.1120G&db_key=AST
| Hβ Photometry for the Association i Lacertae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961ApJ...133..860C&db_key=AST
| A Study of the i Lacertae Association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...129..601H&db_key=AST
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