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Mapping the contours of the Local bubble: preliminary results
We present preliminary results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,taking advantage of Hipparcos stellar distances. Equivalent widths ofthe NaI D-line doublet at 5890 Å are presented for thelines-of-sight towards some 143 new target stars lying within 300 pc ofthe Sun. Using these data which were obtained at the Observatoire deHaute Provence, together with previously published NaI absorptionmeasurements towards a further 313 nearby targets, we present absorptionmaps of the distribution of neutral gas in the local interstellar mediumas viewed from 3 different galactic projections. In particular, thesemaps reveal the Local Bubble region as a low neutral densityinterstellar cavity in the galactic plane with radii between 65-250 pcthat is surrounded by a (dense) neutral gas boundary (or ``wall''). Wehave compared our iso-column contours with the contours derived bySnowden et al. (\cite{snowden98}) using ROSAT soft X-ray emission data.Consistency in the global dimensions derived for both sets of contoursis found for the case of a million degree hot LB plasma of emissivity0.0023 cm(-6) pc with an electron density of 0.005 cm(-2) . We havedetected only one relatively dense accumulation of cold, neutral gaswithin 60 pc of the Sun that surrounds the star delta Cyg, and note thatthe nearest molecular cloud complex of MBM 12 probably resides at thevery edge of the Local Bubble at a distance of ~ 90 pc. Our observationsmay also explain the very different physical properties of the columnsof interstellar gas in the line-of-sight to the two hot stars epsilonCMa and beta CMa as being due to their locations with respect to theBubble contours. Finally, in the meridian plane the LB cavity is foundto be elongated perpendicularly to the Gould's Belt plane, possiblybeing ``squeezed'' by the expanding shells of the Sco-Cen andPerseus-Taurus OB associations. Tables 1 and 2 are also available inelectronic form at the CDS (Strasbourg) via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Distances to the High Galactic Latitude Molecular Clouds G192-67 and MBM 23-24
We report on distance determinations for two high-Galactic latitudecloud complexes, G192-67 and MBM 23-24. No distance determination existsin the literature for either cloud. Thirty-four early-type stars wereobserved toward the two clouds, more than half of which have parallaxesmeasured by the Hipparcos satellite. For the remaining stars, we havemade spectroscopic distance estimates. The data consist ofhigh-resolution echelle spectra centered on the Na I D lines and wereobtained over six nights at the Coudé Feed telescope at Kitt PeakNational Observatory. Interstellar absorption lines were detected towardsome of the stars, which enabled estimates of the distances to theclouds of 109+/-14 pc for G192-67 and 139+/-33 pc for MBM 23-24. Wediscuss the relationship of these clouds to other ISM features such asthe Local Hot Bubble and the local cavity in neutral hydrogen.
| Synthetic Color Indices of Spectrophotometric Standards
Synthetic B--V color indices in the {\it WBVR photometric system for 11stars of 3 -- 4 mag, proposed as spectrophotometric standards, arecalculated for the mean energy distribution data from the Moscow andAlma-Ata spectrophotometric catalogs. Also, synthetic B--V color indicesin the same photometric system are obtained for 16 stars of 6 -- 7 magfrom the set of 60 spectrophotometric standards observed at theSternberg Institute Crimean Station. Both sets of spectrophotometricstandards demonstrate a good agreement between the synthetic andobserved color indices. The energy distribution of Vega is compared withthe mean energy distribution for A0 V-type stars. A pecularity of theenergy distribution of Vega in the ultraviolet range is discussed.
| Radial velocity measurements. II - Ground-based observations of the program stars for the HIPPARCOS satellite
New radial velocities for 446 stars of magnitude 9.0 or brighter in 1616-sq-deg fields of the Northern Hemisphere are determined by automaticPDS measurement of 80-A/mm-dispersion spectra obtained at theObservatoire de Haute Provence using a 17-cm-diameter objective prism.The fields were selected to provide data for the input catalog of theESA Hipparcos astrometric satellite. The measurement techniques andprecision are discussed, and the results are presented in extensivetables and graphs.
| A remarkable eclipsing star in Lyncis - SVS 1740.
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