Above and Below the Substellar Limit at High Resolution

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

" Above and Below the Substellar Limit at High Resolution" AST- 0098468 Spectacular advances have been made recently in our knowledge of brown dwarfs and other objects near the substellar limit. The foundation of the program is the continued use of the Keck telescopes and their various instruments. Work carried out under this award will build on and expand upon the pioneering work which has been done during the last few years. Four goals are outlined. (1) To understand the binary frequency among low-mass objects and to investigate the orbital characteristics of binary stars. Observations will include echelle spectroscopy in the optical and infrared to look for radial velocities. Adaptive optics will be utilized to search for sub-arcsecond companions of known low-mass stars. (2) To test the extension of the substellar mass function down to the boundary between brown dwarfs and planets. This will be done with low-resolution spectra, principally to test for the presence of lithium. (3) Analysis of atomic and molecular line profiles in the optical and near infrared will yield information about the physical conditions within very cool stellar atmospheres. (4) An effort to understand what happens to the stellar magnetic activity at the low-luminosity, low-mass end of the main sequence. It is suspected that normal stellar activity, similar to that which we observe in the sun, is greatly diminished in these stars. The observations will be supplemented by state-of-the-art theoretical modeling of the stellar atmospheres with special attention to dust opacity and partial element depletions.