Cool Stars 14 - Submitted Abstract # 135
This version created on 05 October 2006

Substellar Mass Objects in the Orion OB1a and OB1b Association


Jacqueline Faherty, Stony Brook University
Frederick Walter, Stony Brook University
William Sherry, National Optical Astronomy Observatory

Multicolor photometry is a proven method for finding very low mass
objects.  Followup JHK imaging and near-IR spectroscopy of two dozen
very red (V-I>4) objects in the Orion OB1a and OB1b associations
reveals the coolest and lowest mass PMS candidates in the association.
These objects are mostly unreddened mid-to-late M spectral type
objects (M6-M9) that fall on a few million-year isochrone.  Masses are
largely substellar reaching as low as 0.02 solar masses (20  Jovian
Masses).  The space density of the substellar objects is high.  In
this poster, we will speculate on why the density of substellar-mass
objects appears so large in this fossil star forming region, and on
implications for the initial mass function and the brown dwarf
population in associations.

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