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The 78th Name-List of Variable Stars
We present the next regular Name-List of variable stars containinginformation on 1706 variable stars recently designated in the system ofthe General Catalogue of Variable Stars.
| Variable HST guide stars (I)
We have performed time series analyses on more than 4500 sets of HubbleSpace Telescope (HST) Fine Guidance Sensor (FGS) data, obtained fromabout 3600 guide stars in the period from August 1992 to December 1995.We discuss here a subset of 20 stars that were found to be variable at ahigh confidence level. This subset contains all definite variables inour sample for which at least spectral type, B-V, or Strömgrencolors, respectively, are available. Our variability survey ischaracterized by comparably high photometric accuracy and high timeresolution. The time base of a data set for a given guide star can rangefrom half an hour to several days and even up to years in some cases.The elimination of scintillation noise in a space-borne experiment andthe usage of the identical instrument throughout the survey results invery homogeneous data with a typical photometric precision of about 500ppm, and with a best case of 50 ppm. Half of the cases discussed hereare probably delta Sct variables, and two are eclipsing binaries. Wehave also found four K-type stars with a photometric period of a fewhours, which is difficult to interpret as rotation. Currently, severalspace missions are in preparation, dedicated to high precisionphotometry with the goal of applying asteroseismic techniques to asignificant sample of stars. The HST-FGS data provide an excellenttesting ground for modelling the photometric characteristics of suchspace experiments and for gaining experience in handling the issuesrelated to the respective data and algorithms. Based on observationsmade with the NASA/ESA Hubble Space Telescope, obtained from the dataarchive at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS5-26555.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| A 1.5 GHz radio survey of the Hyades open stellar cluster
Results of a radio survey of the Hyades open stellar cluster carried outwith the VLA at 1.5 GHz are reported. Seventeen fields containing over150 cataloged stars were mapped down to a limiting sensitivity rangingfrom 0.3 mJy at the centers of the fields to 0.9 mJy at a distance of 20arcmin from field centers. Two stars were detected as radio sources: theevolved spectroscopic binary V471 Tau, consisting of a white dwarf and ared dwarf; and the apparently premain-sequence G+K star spectroscopicbinary HD 27130. The failure to detect any single stars as radio sourcesis generally consistent with the age-rotation-activity paradigm,according to which stellar activity is due to magnetic fields producedby dynamo action in rapidly rotating stars and should decrease with ageas a star spins down due to magnetic braking. It is concluded that theHyades M dwarf population is not more active at radio wavelengths thanthe nearby flare star population, or else the number of flare stars inthe Hyades is much less than presently assumed.
| A search for weak H-alpha emission line pre-main-sequence stars
A spectroscopic survey of 177 stars brighter than about 12.5 in R nearfour dark clouds in an effort to find pre-main-sequence (PMS) stars withweak H-alpha emission is reported. A number of such stars have beenfound previously in X-ray images of star formation clouds. Six newcandidate PMS stars with EW (H-alpha) between 0.4 and 4.2 A, in additionto four X-ray discovered stars, are found in the L1551 and L1529 cloudsin the Taurus-Auriga complex. The total number of pre-main-sequencestars in these clouds appears to be about two times the number of strongemission line T Tauri stars.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Bika |
| Rektaszcenzió: | 04h32m10.19s |
| Deklináció: | +17°43'18.2" |
| Vizuális fényesség: | 11.12 |
| RA sajátmozgás: | -0.7 |
| Dec sajátmozgás: | -4.9 |
| B-T magnitude: | 11.745 |
| V-T magnitude: | 11.172 |
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