R associations. VI - The reddening law in dust clouds and the nature of early-type emission stars in nebulosity from a study of five associations

Abstract

view Abstract Citations (85) References (49) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS R associations .VI. The reddening law in dust clouds and the nature of early-type emission stars in nebulosity from a study of five associations. Herbst, W. ; Miller, D. P. ; Warner, J. W. ; Herzog, A. Abstract Positions, identification charts, UBVRIKLMN photometry and spectral types are given for stars, illuminating reflection nebulae that are visible on the POSS prints, which have been identified in five associations. With a ratio of total to selective extinction of 4.2, the reddening law applicable to the dust clouds in which the stars are embedded is steeper than normal. The five associations exhibit 18 early-type stars with circumstellar shells, of which those with spectral types earlier than B5 characteristically have weak IR excesses, in contrast to the strong excesses indicative of circumstellar dust, of later-type stars. Color-magnitude charts show a distribution lying above the ZAMS by up to about 2 mag for both the circumstellar shell stars and those classified as rapid rotators. It is suggested that (1) rapid rotation accounts for the scatter in the color-magnitude diagram, and (2) many of the nebulous early-type emission-line stars are rapid rotators rather than pre-main sequence objects. Publication: The Astronomical Journal Pub Date: January 1982 DOI: 10.1086/113085 Bibcode: 1982AJ.....87...98H Keywords: Cosmic Dust; Early Stars; Interstellar Extinction; Interstellar Matter; Nebulae; Stellar Spectra; Color-Magnitude Diagram; Emission Spectra; Hertzsprung-Russell Diagram; Molecular Clouds; Shell Stars; Stellar Envelopes; Stellar Evolution; Astronomy full text sources ADS | data products SIMBAD (90) GCPD (1) Related Materials (4) Part 1: 1975AJ.....80..212H Part 2: 1975AJ.....80..503H Part 3: 1975AJ.....80..683H Part 4: 1976AJ.....81..840H