Observations of the interstellar band at lambda 4430.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of the interstellar band at lambda 4430. Duke, Douglas Abstract In order to study the broad interstellar band at X 4430 the central absorptions of this band have been measured for more than 400 stars. The dispersion used was that of the Yerkes Spectral Atlas, which is sufficient because of the great width of about 50 A which the band attains. This has made it possible to obtain simultaneously accurate spectral types, luminosities and color excesses. Band depths up to 22 per cent have been found, indicating a maximum equivalent width of more than 6 A. Comparison with other observers shows that no systematic errors are apparent; the probable error of a single determination is slightly larger than one per cent. The correlation of the absorption of X 443b with color excess is excellent; however, there are a few well-substantiated cases where very strong band intensity occurs with only moderate color excess. Also a large fraction of the distant stars at high galactic latitude show intensities which appear to be greater than those expected from their nearly negligible reddening. There appears to be a very weak but definite correlation of band intensity with distance when stars in a narrow range of color excess are considered. Comparison of a X 4430 chart with data on the surface brightness of the Milky Way indicates a close correlation of regions of maximum band intensity with those of maximum absorption. An interstellar D-line versus X 4430 plot shows a definite correlation; however, the scatter is larger than in the case of reddening so that it may be due largely to correlation of both with distance. The data is therefore inconclusive as to the coincidence of regions where the D lines and 4430 are produced. The correlation of 4430 intensity with the intensity of the diffuse interstellar band at X 6284 is good. The observed data indicates that the 4430 absorption is produced largely in regions where interstellar reddening occurs, although they do not appear to result from the same agent. Therefore appreciable deviations from the average ratio of these quantities occur occasionally when large numbers of stars are considered. Yerkes Observatory, Williams Bay, Wis. Publication: The Astronomical Journal Pub Date: October 1950 DOI: 10.1086/106447 Bibcode: 1950AJ.....55R.168D full text sources ADS |