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The outskirts of Cygnus OB2
Context: Cygnus OB2 is one of the richest OB associations in the localGalaxy, and is located in a vast complex containing several otherassociations, clusters, molecular clouds, and HII regions. However, thestellar content of Cygnus OB2 and its surroundings remains rather poorlyknown largely due to the considerable reddening in its direction atvisible wavelength. Aims: We investigate the possible existence of anextended halo of early-type stars around Cygnus OB2, which is hinted atby near-infrared color-color diagrams, and its relationship to CygnusOB2 itself, as well as to the nearby association Cygnus OB9 and to thestar forming regions in the Cygnus X North complex. Methods: Candidateselection is made with photometry in the 2MASS all-sky point sourcecatalog. The early-type nature of the selected candidates is confirmedor discarded through our infrared spectroscopy at low resolution. Inaddition, spectral classifications in the visible are presented for manylightly-reddened stars. Results: A total of 96 early-type stars areidentified in the targeted region, which amounts to nearly half of theobserved sample. Most of them have featureless near-infrared spectra asexpected from OB stars at the available resolution. Another 18 starsthat display Brackett emission lines can be divided between evolvedmassive stars (most likely Be stars) and Herbig Ae/Be stars based ontheir infrared excesses. A component associated with Cygnus OB9/NGC 6910is clearly identified, as well as an enhancement in the surface densityof early-type stars at Cygnus X North. We also find a field population,consisting largely of early B giants and supergiants, which is probablythe same as identified in recent studies of the inner 1° circlearound Cygnus OB2. The age and large extension of this populationdiscards a direct relationship with Cygnus OB2 or any other particularassociation. Conclusions: Earlier claims of the possible large extentof Cygnus OB2 beyond its central, very massive aggregate seem to bedismissed by our findings. The existence of a nearly ubiquitouspopulation of evolved stars with massive precursors suggests a massivestar formation history in Cygnus having started long before theformation of the currently observed OB associations in the region.Based on observations collected at the Centro AstronómicoHispano-Alemán (CAHA) at Calar Alto, operated jointly by theMax-Planck Institut für Astronomie and the Instituto deAstrofísica de Andalucía (CSIC).Tables 1-9 are only available in electronic form at http://www.aanda.org
| A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)
The LSPM catalog is a comprehensive list of 61,977 stars north of theJ2000 celestial equator that have proper motions larger than 0.15"yr-1 (local-background-stars frame). The catalog has beengenerated primarily as a result of our systematic search for high propermotion stars in the Digitized Sky Surveys using our SUPERBLINK software.At brighter magnitudes, the catalog incorporates stars and data from theTycho-2 Catalogue and also, to a lesser extent, from the All-SkyCompiled Catalogue of 2.5 million stars. The LSPM catalog considerablyexpands over the old Luyten (Luyten Half-Second [LHS] and New LuytenTwo-Tenths [NLTT]) catalogs, superseding them for northern declinations.Positions are given with an accuracy of <~100 mas at the 2000.0epoch, and absolute proper motions are given with an accuracy of ~8 masyr-1. Corrections to the local-background-stars propermotions have been calculated, and absolute proper motions in theextragalactic frame are given. Whenever available, we also give opticalBT and VT magnitudes (from Tycho-2, ASCC-2.5),photographic BJ, RF, and IN magnitudes(from USNO-B1 catalog), and infrared J, H, and Ks magnitudes(from 2MASS). We also provide an estimated V magnitude and V-J color fornearly all catalog entries, useful for initial classification of thestars. The catalog is estimated to be over 99% complete at high Galacticlatitudes (|b|>15deg) and over 90% complete at lowGalactic latitudes (|b|>15deg), down to a magnitudeV=19.0, and has a limiting magnitude V=21.0. All the northern starslisted in the LHS and NLTT catalogs have been reidentified, and theirpositions, proper motions, and magnitudes reevaluated. The catalog alsolists a large number of completely new objects, which promise to expandvery significantly the census of red dwarfs, subdwarfs, and white dwarfsin the vicinity of the Sun.Based on data mining of the Digitized Sky Surveys (DSSs), developed andoperated by the Catalogs and Surveys Branch of the Space TelescopeScience Institute (STScI), Baltimore.Developed with support from the National Science Foundation (NSF), aspart of the NASA/NSF NStars program.
| CCD measurements of visual double stars made with the 74 cm and 50 cm refractors of the Nice Observatory (2nd series)
We present 619 measurements of 606 visual double stars made by CCDimaging from 1996 to 1999 with the 74 cm and 50 cm refractors of theNice observatory. Angular separation, position angle and magnitudedifference are given. Magnitude differences estimated from CCD imagesare compared with magnitude differences given in the Hipparcos catalog.The residuals in angular separation and position angle are computed forbinaries with known orbit. Table 2 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/378/954
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Observations of double stars and new pairs. XIV
Results of a continuing survey of visual double stars are presented,including 4880 measurements made from February 1987 to November 1989.The positions in WDS format and Durchmusterung numbers are given for 194pairs first reported here. Micrometer measurements of 1142 doubles madewith the Swarthmore 61 cm refractor are presented. Magnitudes areestimated for some of the objects. Plate measurements, plateorientations, position angles, number of nights, and measured exposuresare given. Visual observations of 342 pairs obtained in May 1989 atCerro Tololo, mostly with the 1.0 m reflector, are reported.
| Photoelectric Photometry of Stars in the Vilnius System in the Area of the North America and Pelican Nebulae
Not Available
| Micrometer observations of double stars.8.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975ApJS...29..315H&db_key=AST
| Measures of 313 doubles stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963AJ.....68..114W&db_key=AST
| Bright Late M-Type Stars Near the Galactic Equator.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...120..118N&db_key=AST
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Observation and Astrometry data
| Constellation: | Cygnus |
| Right ascension: | 20h37m29.69s |
| Declination: | +42°33'14.6" |
| Apparent magnitude: | 9.491 |
| Proper motion RA: | -108.7 |
| Proper motion Dec: | -153.1 |
| B-T magnitude: | 10.484 |
| V-T magnitude: | 9.573 |
Catalogs and designations:
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