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β Cephei stars in the ASAS-3 data. II. 103 new β Cephei stars and a discussion of low-frequency modes
Context: The β Cephei stars have been studied for over a hundredyears. Despite this, many interesting problems related to this class ofvariable stars remain unsolved. Fortunately, these stars seem to bewell-suited to asteroseismology. Hence, the results of seismic analysisof β Cephei stars should help us to better understand pulsationsand the main sequence evolution of massive stars, particularly theeffect of rotation on mode excitation and internal structure. It istherefore extremely important to increase the sample of known βCephei stars and select targets that are useful for asteroseismology. Aims: We analysed ASAS-3 photometry of bright early-type stars with thegoal of finding new β Cephei stars. We were particularly interestedin β Cephei stars that would be good for seismic analysis, i.e.,stars that (i) have a large number of excited modes; (ii) showrotationally split modes; (iii) are components of eclipsing binarysystems; (iv) have low-frequency modes, that is, are hybrid βCephei/SPB stars. Methods: Our study was made with a homogeneous sampleof over 4100 stars having MK spectral type B5 or earlier. For thesestars, the ASAS-3 photometry was analysed by means of a Fourierperiodogram. Results: We have discovered 103 β Cephei stars,nearly doubling the number of previously known stars of this type. Amongthese stars, four are components of eclipsing binaries, seven have modesequidistant or nearly equidistant in frequency. In addition, we foundfive β Cephei stars that show low-frequency periodic variations,very likely due to pulsations. We therefore regard them as candidatehybrid β Cephei/SPB pulsators. All these stars are potentially veryuseful for seismic modeling. Moreover, we found β Cephei-typepulsations in three late O-type stars and fast period changes in one, HD168050.Table 2 and Figs. 2-14 are only available in electronic form athttp://www.aanda.org The V photometry for all 103 stars is available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/477/917
| New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
| Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| Far-Ultraviolet Stellar Photometry: Fields Centered on rho Ophiuchi and the Galactic Center
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..104..101S&db_key=AST
| A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
| 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.
| A study of visual double stars with early type primaries. IV Astrophysical data
Astrophysical parameters (MK class, color excess, absolute magnitude,distance, effective temperature, mass, and age) are derived fromcalibrations of the uvby-beta indices for the members of 253 doublestars with O or B type primaries and faint secondaries. The photometricspectral classification is compared to the MK classes, and the agreementis very good. The derived data together with spectroscopic and JHKL dataare used for deciding which pairs are likely to be physical and whichare optical, and it is shown that 98 (34 percent) of the secondaries arelikely to be members of physical systems. For 90 percent of the physicalpairs the projected separation between the components is less than25,000 AU. A majority of the physical secondaries are late-type stars,and 50 percent of them are contracting towards the zero-agemain-sequence. Also presented are new uvby-beta data for 43 secondariesand a computer program for determining astrophysical parameters fromuvby-beta data.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| A study of visual double stars with early type primaries. II - Photometric results
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983A&AS...51..161L&db_key=AST
| A study of visual double stars with early type primaries. I - Spectroscopic results
Attention is given to spectral peculiarities found in data on thespectral classes of 486 stars in 254 visual doublet or multiplet systemswith O or B type primaries, in order to isolate a group of very youngstars that may serve for the study of early stellar evolutioncharacteristics. It is noted that the material contains a substantialfraction of secondaries that are likely to be physical, and that severalof these may be in the premain-sequence phase of stellar evolution, orhave reached the zero-age main sequence.
| UBV-/H-beta/ photometry of luminous stars between L equals 335 deg and L equals 6 deg
Results are reported for photoelectric UBV and H-beta photometry of 316luminous OB stars and early-type supergiants in the region between 335and 6 deg galactic longitude. UBV magnitudes for the 316 stars and betaindexes for 37 of them are presented. Absolute magnitudes, distances,and color excesses are determined for the 161 stars with measured betaindexes or known MK spectral types. The results are discussed in termsof the spiral structure of the Galaxy. From the data obtained forprogram stars assumed to be cluster members, distances are derived forthe open clusters NGC 6167 (1.7 kpc), NGC 6193 (1.3 kpc), Hogg 22 (2.0kpc), NGC 6231 (1.9 kpc), and Tr 27 (1.6 kpc).
| Four-colour and H-beta photometry for early type stars in three southern galactic regions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41...85L&db_key=AST
| Determination of proper motions in the region of the association Scorpius OB1
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| Takýmyýldýz: | Akrep |
| Sað Açýklýk: | 16h47m34.33s |
| Yükselim: | -42°52'36.3" |
| Görünürdeki Parlaklýk: | 8.261 |
| Uzaklýk: | 540.541 parsek |
| özdevim Sað Açýklýk: | -3 |
| özdevim Yükselim: | -0.7 |
| B-T magnitude: | 8.503 |
| V-T magnitude: | 8.281 |
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