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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.
| Coronal X-ray sources in the Hyades: A 40 kilosecond ROSAT pointing
We present results of a 40 ks ROSAT pointed observation of the Hyadescluster. The limiting Lx is approximately = 2 x1027 ergs/sec at field center, increasing to approximately =2 x 1028 ergs/sec at 40 min off-axis. This represents themost sensitive X-ray observation to date in the Hyades region. More than30 sources have been detected in the Position Sensitive ProportionalCounter (PSPC) standard processing, of which 15 are Hyades members, fiveare cluster candidates that are likely non-members, four are foregroundor background stars, and the remainder are unidentified. One Hyad, VB173 (= VA 276), lies in a confused region, but is detected as a distinctsource in the soft band only (E approximately less than 0.5 keV). Wereport upper limits for four other Hyades members in our field, all Mdwarfs. Of the 16 Hyades detections, two represent the opticallyfaintest members seen to date in X-rays; VA 260 (V = 16.68) and VA 368(V = 16.25). These are both M dwarfs of mass approximately = 0.15-0.2solar mass and are fully convective stars according to current theory.Analysis of X-ray light curves using 1 ks bins indicates somevariability in the strongest sources and a possible flare in VA 383. TwoHyades stars, VB 141 and VB 71, were also detected with the co-alignedWide Field Camera (WFC) EUV instrument. VB 141, the second brightestX-ray source in the Hyades, remains an enigma: a rapidly rotating FOstar with a fainter, long-period companion, this object has an X-rayspectrum indicative of strong coronal activity. X-ray pulse-heightanalysis demonstrates that coronal models with at least two temperaturesare required for most of the stronger X-ray sources. The ROSAT X-rayspectra generally require higher temperatures for the hotter componentin the M dwarfs compared to the F-G dwarfs.
| A radial-velocity survey of the Hyades
Photoelectric radial-velocity measurements, obtained with external erroras small as 0.1 km/s using the 200-inch Hale telescope at PalomarObservatory during the period 1971-1986, are reported for over 400candidate members (with V magnitude between 6 and 14) of the Hyadescluster. The history of Hyades observations is recalled; the Palomarinstrumentation and observing program are described; the data-reductionand standardization procedures are discussed in detail; and the data arepresented in extensive tables and graphs. About 200 of the stars areclassified as cluster members, including 60 spectroscopic binaries.
| Photometry of possible members of the Hyades cluster III
Photoelectric photometry in BVRI colors has been obtained for 61 starsin the region surrounding the Hyades cluster. Almost all stars observedhere were found by Giclas or Luyten to possess proper motions resemblingthose of confirmed Hyades members. They cover the ranges between 0.6 and1.7 in (B-V) and 0.2 and 1.3 in (R-I) and are thus mostly late G, K, andearly M stars. Of these 61 stars, only 24 are found to be probablemembers and five are found to be possible members from their positionsin either the V,(B-V) or V,(R-I) diagrams. Nonetheless, these probablemembers enrich the cluster well beyond the list of Pels, Oort, andPels-Kluyver, especially in its southwestern quadrant.
| A study of the motion, membership, and distance of the Hyades cluster
Particular attention is given to the role of the convergent-point, ormoving cluster, method in the determination of the Hyades distance, andthe apparent discrepancy between its results and those of other Hyadesdistance indicators. The Hyades photographic plate material isconsidered along with the approaches used in the measurements, propermotion reductions, coordinate reductions, and aspects of photography.Problems of cluster membership determination are also discussed.
| Low-luminosity members of the Hyades cluster. II.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969AJ.....74....2V&db_key=AST
| Low-luminosity members of the Hyades cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966AJ.....71..482V&db_key=AST
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Группы:
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Наблюдательные данные и астрометрия
| Созвездие: | Телец |
| Прямое восхождение: | 04h27m02.17s |
| Склонение: | +15°22'24.6" |
| Видимая звёздная величина: | 11.216 |
| Собственное движение RA: | 51.8 |
| Собственное движение Dec: | -17.6 |
| B-T magnitude: | 11.859 |
| V-T magnitude: | 11.27 |
Каталоги и обозначения:
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