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Reddening and the Extinction Law at High Galactic Latitude
We present near-infrared (JHKL) photometry of 103 southern stars locatedbehind translucent interstellar clouds at high Galactic latitude. Ourdata are combined with visual photometry and spectral type informationfrom the literature in a detailed analysis of the wavelength dependenceof interstellar extinction by dust in these high-latitude clouds. Weinvestigate the shape of the near-infrared extinction curve and evaluatethe total line-of-sight extinction (AV) and ratio oftotal-to-selective extinction (RV) in each line of sight.Sources of uncertainty in RV arising from photometric errorsand spectral classification errors are carefully assessed and quantifiedas functions of the line-of-sight reddening. We detect appreciabledifferences in our results compared with the average extinction curvefor dust in the diffuse interstellar medium (ISM) close to the Galacticplane. Assuming a power-law form in the near-infrared, we find the meanfor high-latitude clouds to be well described by~λ-2.3, somewhat steeperthan that for the diffuse ISM(~λ-1.8). Our sampleincludes a substantial number of lines of sight with low RVvalues (47% with RV<2.8) relative to the diffuse ISMaverage of 3.05+/-0.15. We conclude that many high-latitude clouds haveenhanced abundances of relatively small grains.
| Polarimetry of the young Herbig AE star HD 139614. Differences of polarimetric behaviour of Vega-type stars
We present optical polarimetric data of the Herbig Ae star HD 139614 anddiscuss its behaviour relative to similar stars. In spite of a low levelof polarization (~ 0.05-0.2%), polarimetric variability on a time-scaleof days was detected during a four night synoptic study. The differencein the level of the polarization for HD 139614 relative to other HerbigAe/Be stars such as HD 141569, HD 142666 and HD 169142 might be due tothe inclinations and viewing aspects of their circumstellar disks and totheir different evolutionary stages. This hypothesis is consistent withthe photometric behaviour of these stars, their v sin i values andspectral energy distribution in the near and far IR.
| Stars with ISM Polarization Observed with HPOL
Polarization data are given for stars whose polarizations are mostlyinterstellar which were observed for various programs with theUniversity of Wisconsin spectropolarimeter (HPOL) during 1989-1994.
| The nearby 2-solar mass BOK globule LBN 11 - Sub-sonic molecular clumps in a magnetic environment
A multiwavelength study of the nearby small Bok globule LBN 11 isperformed in order to investigate the relationship between embeddedmagnetic fields, cloud structure, and star formation. Opticalpolarimetry of background stars is used to characterize and trace theembedded magnetic field direction. High-dispersion CO isotopic mappingis employed to determine the radial density distribution of the gas,measure cloud rotation, and identify individual gas clumps. CS and SOmapping revealed dense cores within the (C-13)O clumps. Analysis ofcoadded IRAS images reveal the cloud to be free of current or recentstar formation: there are no IR point sources of sufficient flux orproper colors to signify young stars associated with the cloud. Themolecular line maps show the cloud to be extremely clumpy. Clumps arefound to range in size from 0.2 pc for the largest CO clump to about0.04 pc for the smallest CS feature. It is concluded that, at least inthe envelope of the cloud, the magnetic field and the CO clumps arecoupled.
| Toward selection of intermediate-magnitude polarization standards
The Minipol optical polarimeter with a V-band filter was used to observe16 summer intermediate-magnitude (mB = about 9) stars from the survey ofMathewson and Ford (1970). These stars were chosen to span polarizationpercentages from zero to almost 6 percent and to cover a large range ofpolarization position angles. The primary reason for reobserving thesestars was to determine their V-band polarization properties and toidentify polarization variables, which are unsuitable standards. TheMinipol observations showed that 12 of the stars had V-bandpolarizations that were very similar to the Mathewson and Ford B-bandvalues. One star had a significantly different polarization positionangle and two had significantly different percentage polarizations. Onestar, HD 161306, was wildly different in both percentage polarizationand position angle.
| Stromgren and H-beta photometry of stars earlier than G0 in 5 areas containing high latitude molecular clouds
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989A&AS...80..127F&db_key=AST
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