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GPM - compiled catalogue of absolute proper motions of stars in selected areas of sky with galaxies.
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| On the nearest molecular clouds. III - MBM 40, 53, 54, and 55
In an attempt to determine the distances to four high-latitude molecularclouds (HLCs), echelle spectra near the Na I D lines, accurate MKspectral types, and photoelectric photometry for 25 nearby stars havebeen obtained. Fairly firm distance limits may be placed on MBM 40 (dsmaller than or equal to 140 pc) and MBM 53 (d greater than or equal to110 pc and less than or equal to 155 pc), based on the presence orabsence of strong interstellar Na I absorption towards stars projectedon or near those HLCs. Weak interstellar absorption lines observedtoward many of the stars located near MBM 54 and 55 make the distancesto those clouds less certain (about 265 pc for both). Interstellar CHabsorption at 4300 A was detected in the spectrum of HD 218662, locatedbehind MBM 53 with a CH column density of 2.1 x 10 to the 13th per sqcm, thus implying a CH abundance comparable to that observed in othermolecular clouds. Morphological and velocity agreement among COemission, the Na I absorption, the 100 micron infrared cirrus emission,and the 21 cm H I emission near these HLCs suggest a close associationof the interstellar material responsible for those phenomena.
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