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The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A new class of rapidly pulsating star - IV. Oscillations in EC 20117-4014 and atmospheric analyses
A new class of pulsating stars, the EC 14026 stars, has recently beenannounced. We report the discovery of rapid oscillations in EC20117-4014. The oscillations are multiperiodic with three periodsdetected so far: 137.3, 142.1 and 158.7s. The peak-to-peak amplitude ofthese oscillations is ~1 per cent. Along with the spectrum and UBVcolours, this implies that EC 20117-4014 is another member of the newclass. Interestingly, there is evidence for period/phase changes in themain 137.3-s period, as no linear ephemeris can be found that will fitthe collection of light curves we have obtained. We interpret theoscillations as pulsations of an sdB star in a binary with an F/Gcompanion, as indicated by the optical spectra. In order to deriveatmospheric parameters of the component stars, low- (~3.5A) andintermediate- (~1A) resolution optical spectroscopy is presented for thefirst four EC 14026 stars to be discovered: EC 14026-2647, EC10228-0905, EC 20117-4014 and PB 8783. Their spectra are modelled as thecombination of sdB and F/G stars using a grid of high-gravity modelatmospheres to represent the former, and observed spectra to representthe latter. The spectral types of the late-type companions are estimatedto be in the range early F to early G. Atmospheric parameters for thesdB components of the four stars are derived and found to be similar:log g~6.0 and T_eff~35 000K. If the late-type companions are on or nearthe main sequence, their distances agree with those estimated for thesdB components, assuming that the masses of the latter are ~0.5Msolar.The evolutionary status of the four stars strongly suggests that the sdBcomponent has suffered substantial mass loss by Roche lobe overflow,along the lines originally proposed by Mengel et al. This hypothesis canbe tested by using the orbital time delay in the pulsations to measurethe binary period and separation. The discovery of pulsations in sdBstars is important: asteroseismological studies to probe their structureand evolutionary time-scale can now be contemplated.
| Ca II H and K Filter Photometry on the UVBY System. II. The Catalog of Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....109.2828T&db_key=AST
| Optical Polarization of 1000 Stars Within 50-PARSECS from the Sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101..551L&db_key=AST
| Interstellar polarization from observations of A and F stars in high and intermediate galactic latitudes, and from stars in the Mathewson and Ford polarization catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986A&AS...64..487K&db_key=AST
| Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. III - 790 late-type bright stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...15A&db_key=AST
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| Takýmyýldýz: | Tukan |
| Sað Açýklýk: | 22h44m16.50s |
| Yükselim: | -60°29'58.0" |
| Görünürdeki Parlaklýk: | 6.3 |
| Uzaklýk: | 135.501 parsek |
| özdevim Sað Açýklýk: | 0.7 |
| özdevim Yükselim: | 20.6 |
| B-T magnitude: | 6.975 |
| V-T magnitude: | 6.363 |
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