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The Metamorphosis of SN 1998bw
We present and discuss the photometric and spectroscopic evolution ofthe peculiar SN 1998bw, associated with GRB 980425, through an analysisof optical and near-IR data collected at ESO-La Silla. The spectroscopicdata, spanning the period from day -9 to day +376 (relative to Bmaximum), have shown that this supernova (SN) was unprecedented,although somewhat similar to SN 1997ef. Maximum expansion velocities ashigh as 3×104 km s-1 to some extent mask itsresemblance to other Type Ic SNe. At intermediate phases, betweenphotospheric and fully nebular, the expansion velocities(~104 km s-1) remained exceptionally high comparedto those of other recorded core-collapse SNe at a similar phase. Themild linear polarization detected at early epochs suggests the presenceof asymmetry in the emitting material. The degree of asymmetry, however,cannot be decoded from these measurements alone. The He I 1.083 and2.058 μm lines are identified, and He is suggested to lie in an outerregion of the envelope. The temporal behavior of the fluxes and profilesof emission lines of Mg I] λ4571, [O I] λλ6300,6364, and a feature ascribed to Fe are traced to stimulate futuremodeling work. The uniqueness of SN 1998bw became less obvious once itentered the fully nebular phase (after 1 yr), when it was very similarto other Type Ib/c-IIb objects, such as the Type Ib SN 1996N and theType IIb SN 1993J, even though SN 1998bw was 1.4 mag brighter than SN1993J and 3 mag brighter than SN 1996N at a comparable phase. Thelate-phase optical photometry, which extends up to 403 days after Bmaximum, shows that the SN luminosity declined exponentially butsubstantially faster than the decay rate of 56Co. Theultraviolet-optical-infrared bolometric light curve, constructed usingall available optical data and the early JHK photometry presented inthis work, shows a slight flattening starting on about day +300. Sinceno clear evidence of ejecta-wind interaction was found in the late-timespectroscopy (see also the work of Sollerman and coworkers), this may bedue to the contribution of the positrons since most γ-rays escapethermalization at this phase. A contribution from the superposed H IIregion cannot, however, be excluded. Based on observations collected atESO-La Silla.
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| 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.
| An astrometric catalogue of stars in the region of M15
We present positions and proper motions with respect to the PPMcatalogue of 863 stars in a field of 8 deg x 6 deg centered on theglobular cluster M15. The catalogue is based on measurements of 136plates from the Carte du Ciel telescope of Bordeaux, the CERGA Schmidttelescope, and the double refractor of Bonn. The modal accuracy of theproper motions is +/- 0 arcsec 15/100 a.
| UBV photometry of stars whose positions are accurately known. VI
Results are presented from UBV photometric observations of 1000 stars ofthe Bright Star Catalogue and the faint extension of the FK5.Observations were carried out between July 1987 and December 1990 withthe 40-cm Cassegrain telescope of the Kvistaberg Observatory.
| Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
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Наблюдательные данные и астрометрия
| Созвездие: | Пегас |
| Прямое восхождение: | 21h37m06.54s |
| Склонение: | +11°43'10.2" |
| Видимая звёздная величина: | 7.241 |
| Расстояние: | 187.97 парсек |
| Собственное движение RA: | 20 |
| Собственное движение Dec: | 10 |
| B-T magnitude: | 7.344 |
| V-T magnitude: | 7.25 |
Каталоги и обозначения:
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