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Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Another X-Ray-discovered Poor Cluster of Galaxies Associated with CL 0016+16
We report optical spectroscopic observations of RX J0018.8+1602, a ROSATX-ray source proposed to be an intermediate-redshift cluster ofgalaxies. Our observations confirm the identification of RX J0018.8+1602and provide measurements of its mean radial velocity (z = 0.5406 +/-0.0006) and velocity dispersion ( sigma p=200^{+110}_{-80} kms-1). This is the second poor cluster that has been found to be acompanion to CL 0016+16 (z = 0.5455), the other one being RXJ0018.3+1618 (z = 0.5506). The 0.2-2 keV band source-frame X-rayluminosity summed over both companion clusters is 5 x 1044 ergs s-1,which is a significant fraction (~23%) of the X-ray luminosity of themain cluster. The companions are located at angular distances of 10'-25'(minimum physical scales of 5-12 Mpc) from CL 0016+16, and we proposethat they represent a new large-scale component of the X-ray emissionfrom clusters of galaxies. Similar low X-ray luminosity poor clusterssurrounding nearby Abell clusters can explain the excess power observedin the angular cross-correlation function between Abell clusters and theX-ray background on inferred physical scales of 14-20 Mpc.
| 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.
| A study of some stars with circumstellar dust envelopes. I
We present the results of a study of circumstellar dust envelopes of 36stars of early(O-B-A) types in the directions of the associations CasOB1, Cas OB2, Per OB1, and Ori OB1. We determine the absorption at 1640Å, the linear radius of the dust envelopes, the mean value of thecoefficient k, and the masses of the envelopes. They differsignificantly from one another.
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | דגים |
| התרוממות ימנית: | 00h18m42.80s |
| סירוב: | +15°59'25.8" |
| גודל גלוי: | 9.258 |
| מרחק: | 157.978 פארסק |
| תנועה נכונה: | 31.1 |
| תנועה נכונה: | -30.2 |
| B-T magnitude: | 9.88 |
| V-T magnitude: | 9.31 |
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