Photoelectric Measures of the 4430 A Diffuse Interstellar Band

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Abstract
600 photoelectric measures of the 4430 A band are given, mainly for B type stars; 380 stars were measured at Cambridge and 220 at the Radcliffe Observatory. The interagreement of the two sets of measures is satisfactory, and agreement with most other observers is good. Contrary to his assessment, all of Duke's results seem to be reliable. Apart from the O stars measured at Cambridge, which have been rejected because of a systematic error, there is no dependence of the measures on spectral type. The strongest correlation of the 4430 band is with the diffuse interstellar features at 6284 and 5780 A. The correlation with reddening is significantly different between different galactic longitude regions. 4430 is weak relative to reddening in the southern Milky Way and towards Cygnus, particularly weak towards the galactic centre, and strongest towards Monoceros. The SMC appears to show a dependence of 4430 on reddening similar to the Milky Way. Exciting stars of emission nebulosities do not show 4430 systematically weak relative to reddening as some investigators have suggested. Certain stellar groups show a large scatter about the 4430-reddening relation. The correlation predicted by R. Wilson between 4430, polarization, and reddening, has not been found. Attempts to measure excess polarization within the band gave inconclusive results.

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