view Abstract Citations (13) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Structure of the OH/infrared object NML Cygnus. II. Analysis of the OH interferometry. Herbig, G. H. Abstract The 1612-MHz OH interferometry of NML Cyg published by Davies, Masheder, and Booth has been analyzed in terms of pure radial expansion. It is found that the positions and radial velocities of most of the very complex OH structure, which covers an area of about 2'!5 by 3'!5, can be explained by simultaneous ejection about 100 + 20 years ago (if the distance is 500 pc) from a center lying near one edge of the source. The expansion velocity is 46 l 2 km i The three-dimensional map of NML Cyg that can then be constructed shows that all the OH lies in the hemisphere centered at the Earth as seen from the expansion center. It is suggested that the absence of receding OH in this and similar double-peaked OH sources is due to confinement of the OH maser emission to directions away from the infrared pumping source. The radial velocity of the M-type star measured at 0.8 , and the 4.7- CO absorption velocity observed by Geballe, Wollman, and Rank, fit well into this model. The latter spectrum is believed to be produced in material of the expanding shell that is projected upon the infrared source. It may be that the OH maser emission is detectable only at special points in the expanding envelope around the M star. Subject headings: infrared sources - nebulae Publication: The Astrophysical Journal Pub Date: April 1974 DOI: 10.1086/152772 Bibcode: 1974ApJ...189...75H full text sources ADS | data products SIMBAD (3) Related Materials (1) Part 1: 1974ApJ...189...73H