## LSU Historical Dissertations and Theses

#### Title

A Spectroscopic Study of OB+ Stars.

1994

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

#### Department

Physics and Astronomy

John S. Drilling

#### Abstract

We present here the results of an analysis of spectroscopic and photometric observations of OB$\sp+$ stars. These mostly luminous young stars were selected from a survey of the Milky Way that is complete to the 12th B magnitude and covers $360\sp\circ$ of galactic longitude and ${\pm}10\sp\circ$ of galactic latitude. We determined the MK spectral types of 291 OB$\sp+$ stars; a detailed discussion of the MK system and the process of spectral classification is given. Using the MK types and UBV photometry, we derived the distances to these stars and to other OB$\sp+$ stars that had published MK spectral types. We thus have distances to nearly all of the non-emission OB$\sp+$ stars in the Milky Way down to the 12th B magnitude. We derive the space distribution of these stars and compare it with previous studies of Galactic structure. The color excesses derived from these data are plotted to show the distribution of dust in the Galactic plane out to several kpc. As is often the case in surveys of this nature, several astrophysically interesting peculiar spectra were discovered, and these too are described.

76

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