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Radial-velocity measurements. V - Ground support of the HIPPARCOS satellite observation program
The paper presents data on 1070 radial velocity measurements of starsdistributed in 39 fields measuring 4 deg x 4 deg. The PPO series ofFehrenbach et al. (1987) and Duflot et al. (1990) is continued using theFehrenbach objective prism method.
| The local interstellar medium and soft local X-ray radiation
The nature of the soft local X-ray radiation is discussed. The questionof whether the radiation originates from a local bubble, a number ofnonlocal bubbles, or the Galactic corona is examined. Attention is givento Rosat findings and to the known characteristics of the Dracomolecular cloud, the Hercules H I shell, and the Hercules field.
| Interstellar NA I D line studies of stars towards the Draco nebula
This study presents new high-dispersion CCD spectra of sodium for eightprogram stars located in the direction of the high-latitude Dracomolecular cloud (DMC). The derived lower distance limit of 180 pc abovethe Galactic plane was evaluated from nondetection of interstellarabsorption lines of sodium at the Draco velocity in sight lines of B8-F0type stars. This result is in agreement with former distance estimatesfrom star counts as well as from UBV photometric extinctionmeasurements. The existence of the most negative velocity components inspectra of the most distant stars suggests a more speculative distanceestimate of 400-600 pc for the DMC. The present determination of a lowerdistance limit to the DMC from an interstellar absorption-line studysupplements the few existing optical determinations of firm (upper)distance limits to other high-latitude molecular clouds.
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Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Ejderha |
| Sað Açýklýk: | 16h44m17.56s |
| Yükselim: | +60°58'14.5" |
| Görünürdeki Parlaklýk: | 7.89 |
| Uzaklýk: | 148.588 parsek |
| özdevim Sað Açýklýk: | -3 |
| özdevim Yükselim: | 12.5 |
| B-T magnitude: | 8.054 |
| V-T magnitude: | 7.904 |
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