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A spectroscopic survey for lambda Bootis stars. II. The observational data
lambda Bootis stars comprise only a small number of all A-type stars andare characterized as nonmagnetic, Population i, late B to early F-typedwarfs which show significant underabundances of metals whereas thelight elements (C, N, O and S) are almost normal abundant compared tothe Sun. In the second paper on a spectroscopic survey for lambda Bootisstars, we present the spectral classifications of all program starsobserved. These stars were selected on the basis of their Strömgrenuvbybeta colors as lambda Bootis candidates. In total, 708 objects insix open clusters, the Orion OB1 association and the Galactic field wereclassified. In addition, 9 serendipity non-candidates in the vicinity ofour program stars as well as 15 Guide Star Catalogue stars were observedresulting in a total of 732 classified stars. The 15 objects from theGuide Star Catalogue are part of a program for the classification ofapparent variable stars from the Fine Guidance Sensors of the HubbleSpace Telescope. A grid of 105 MK standard as well as ``pathological''stars guarantees a precise classification. A comparison of our spectralclassification with the extensive work of Abt & Morrell(\cite{Abt95}) shows no significant differences. The derived types are0.23 +/- 0.09 (rms error per measurement) subclasses later and 0.30 +/-0.08 luminosity classes more luminous than those of Abt & Morrell(\cite{Abt95}) based on a sample of 160 objects in common. The estimatederrors of the means are +/- 0.1 subclasses. The characteristics of oursample are discussed in respect to the distribution on the sky, apparentvisual magnitudes and Strömgren uvbybeta colors. Based onobservations from the Observatoire de Haute-Provence, OsservatorioAstronomico di Padova-Asiago, Observatório do Pico dosDias-LNA/CNPq/MCT, Chews Ridge Observatory (MIRA) and University ofToronto Southern Observatory (Las Campanas).
| Late A-type stars: new Strömgren photometric calibrations of absolute magnitudes from HIPPARCOS
Hipparcos trigonometric parallaxes have been used to derive aphotometric absolute magnitude calibration of main-sequence late A-typestars in terms of Strömgren photometric indices - accounting fortemperature, evolution and metallicity effects - and projectedequatorial rotational velocities. The derived calibrations are valid formain-sequence normal A3-A9 and metallic Am stars, showing residuals of0.22 and 0.20 magnitudes, respectively. One of the fitting methods used(BCES) allows the derivation of the observational ZAMS in this spectralrange, showing an excellent accordance with theoretical evolutionarymodels. The evolutionary state of the Am stars is also discussed.Table~A1 is only available in electronic form from CDS via anonymous ftp130.79.128.5, and by e-mail: request to cesca@am.ub.es
| Delta a and Stroemgren photometry of stars in the Renson-catalogue of AP and AM stars
We have observed 131 stars of \cite[Renson's (1991)]{re91} catalogue ofAp and Am stars both in the Stroemgren & Maitzen's (1976) Delta asystem as a contribution to the photometric studies of the lambda 5200broad band flux depression feature in chemically peculiar stars. Withfew exceptions the probability grouping of Renson for membership in theCP2 group of peculiar stars is nicely reflected by peculiar values ofDelta a. Comparison with already available Delta a values yieldsslightly larger values due to a minor shift in the filter g_1 samplingthe depression. As found by \cite[Maitzen & Vogt (1983)]{ma83} theGeneva system peculiarity parameters correlate well with Delta a. Thisstudy demonstrates the advantageous performance of a photoelectricphotometer with a rapidly rotating filter wheel moving in a stop and gomode. Tables 3 and 4 are also available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Far-ultraviolet stellar photometry: Fields in Sagittarius and Scorpius
Far-ultraviolet photometry for 741 objects in a field in Sagittariuscentered near M8 and 541 objects in a field centered near sigma Scorpiiis presented. These data were extracted from electographic imagesobtained with two cameras during a shuttle flight in 1991 April/May. Thecameras provided band passes with lambdaeff = 1375 A andlambdaeff = 1781 A. Synthetic colors show that these bandsare sensitive to effective temperature for hot stars. Our measurementswere placed on a quantitative far-ultraviolet magnitude scale byconvolving the spectra of stars observed by IUE with our cameras'spectral response functions. Fifty-eight percent of the ultravioletobjects were identified with visible stars using the SIMBAD databasewhile another 40% of the objects are blends of early type stars tooclose together to separate with our resolution. Our photometry iscompared with that from the TD-1, OAO 2, and ANS satellites and the S201(Apollo 16) far-ultraviolet camera and found to agree at the level of afew tenths of a magnitude. Unlike previous studies, almost half of theidentified visual counterparts to the ultraviolet objects are early Bstars. A plot of distance modulus against ultraviolet color excessreveals a significant population of stars with strong ultravioletexcess.
| Physical investigations of star chains.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&A....41..447H&db_key=AST
| The Kreinin-Murri Method for Absolute Determination of Equatorial-Star Declinations.
Not Available
| Rotational velocities of faint stars of early spectral types.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963AJ.....68..428S&db_key=AST
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Besorolás csoportokba:
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Pozíciós és asztrometriai adatok
| Csillagkép: | Sas |
| Rektaszcenzió: | 22h05m23.72s |
| Deklináció: | +00°15'40.1" |
| Vizuális fényesség: | 7.562 |
| Távolság: | 303.951 parszek |
| RA sajátmozgás: | -1.3 |
| Dec sajátmozgás: | -4.6 |
| B-T magnitude: | 7.896 |
| V-T magnitude: | 7.59 |
Katalógusok és elnevezések:
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INHABITED SKY
