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HD 79241



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The ROSAT all-sky survey catalogue of optically bright OB-type stars.
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.

Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.

Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.

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.

Optical eclipses and precession effects in the X-ray binary system HD 77581=4U 0900-40
Results of an analysis of multiyear series of photometric observationsof the X-ray binary system HD 77581 are presented. It is shown that thesystem is an eclipsing variable in the optical range and displaysregular long-period variability in the shape and amplitude of theoptical light curves with a period of 93.3 days, which may be connectedwith phenomena in the system. It is also shown that the amplitude of theellipsoidality effect of the visible star is about 0.04 mag in the HD77581 system, with the total amplitude of optical variability reaching0.09 mag. The eclipses are caused by gas streams and by the accretionstructure, whose orientation in the binary system varies with theprecession period of the visible star. The relatively small amplitude ofthe ellipsoidality effect corresponds to the incomplete filling of itsRoche lobe by the visible star. The mass of the neutron star isestimated at 1.6 + or - 0.3 solar masses.

Simultaneous ultraviolet, optical, and X-ray observations of the X-ray source VELA X-1 /HD 77581/
UV spectra (obtained by the IUE) of HD 77581, associated with the binaryX-ray source Vela X-1, show a spectrum typical of an early B-typesupergiant. However, the P Cygni profiles of strong resonance lines showsubstantial variations with orbital phase. These variations can beascribed to the changing ionization state in the stellar wind caused bythe X-ray emitting companion. X-ray and spectroscopic and photometricoptical observations, simultaneous with the IUE observations, indicatebehavior consistent with previous epochs.

Intermediate band photometry of early-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..205E&db_key=AST

Spectral classification from the ultraviolet line features of S2/68 spectra. II - Late B-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...30...71C&db_key=AST

Four-colour photometric observations of the X-ray binary star HD 77581 (Vel X-1) I. Observations.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...27..433Z&db_key=AST

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Observation and Astrometry data

Right ascension:09h11m41.00s
Apparent magnitude:6
Distance:392.157 parsecs
Proper motion RA:-20.6
Proper motion Dec:8.9
B-T magnitude:5.863
V-T magnitude:5.984

Catalogs and designations:
Proper Names
HD 1989HD 79241
TYCHO-2 2000TYC 7678-4343-1
USNO-A2.0USNO-A2 0450-08514855
BSC 1991HR 3656
HIPHIP 45127

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