Groups of stars known as OB associations are the birthplaces of the hot and massive O and B stars. They are fossil star formation regions, retaining a complete record of all the stars that formed therein. All the low mass stars that formed in such an OB association are still present, generally unobscured, and are at their final masses. The stars have the same times of birth, and the very low mass stars and substellar mass objects are still sufficiently bright to be easily observable. Since most low mass stars form in OB associations, these regions provide a representative view of low mass star formation in our Galaxy. The observational effort investigates several questions: Are the low mass stars formed in-situ in the Orion OB1b association, with their development arrested by the massive stars, or are they ejected from the association by multi-body gravitational interactions as underdone embryos? What is the distribution of stellar rotation periods, and how do the stars spin up at ages between two and ten million years, an age interval currently not well sampled? New observations will provide a uniform set of mass distribution functions for the stars in a sample of young nearby OB associations, and so we may ask how universal is the low mass end of the initial mass function?
Broader Impact: This project contributes to both undergraduate and graduate astronomy programs at Stony Brook, as well as to local outreach efforts. Large amounts of guaranteed observation time through the Small and Medium Astronomical Research Telescopes System consortium allows research proposals from qualified undergraduates to obtain data for use in the undergraduate courses. To that end, two undergraduate data aides will be employed, and the project will offer research opportunities to others. This support will also enhance outreach to local secondary schools. About 2 high school students per year have been supervised over the past decade for science fair projects. The guaranteed observing time will afford these students a wider range of options for planning, proposing, reducing, and analyzing data on projects of their choosing.
