Spitzer Space Telescope - General Observer Proposal #50058


Circumbinary dust disks - reconciling the theory of close binary evolution with
observation

Principal Investigator: Carolyn Brinkworth
           Institution: Caltech/JPL

     Technical Contact: Carolyn Brinkworth, Caltech/JPL

Co-Investigators: 
Donald Hoard, Spitzer Science Center                                  
Tom Marsh, Univ. of Warwick, UK                                       

Science Category: circumstellar/debris disks 
 Observing Modes: IracMap IrsPeakupImage 
  Hours Approved: 2.8 

Abstract:
The evolution of all close binary systems is driven by the loss of angular
momentum from the system. Standard theory invokes two mechanisms for this loss -
gravitational radiation and magnetic braking - and forms the backbone of
virtually all studies based on binary evolution rates. Recent studies, however,
have shown that the extrapolations in which the standard theory is based are
wrong, suggesting that the true evolutionary rate of binary systems should be 10
- 10000 slower than previously predicted. To confuse the matter further,
observational studies show that binary systems are actually evolving around 1000
times faster than this revised theory suggests, leading to the speculation that
there is another angular momentum loss mechanism at work. One of the more likely
candidates is the presence of a cool, dusty disk around the binary, which drains
angular momentum from the system via tidal coupling. We propose to combine a
Spitzer search for circumbinary dust disks with results from an ongoing project
to directly measure the evolutionary rates of a number of detached binary
systems. By modelling these disks, we will be able to test for any correlation
between disk mass and evolutionary rate, and test whether the presence of these
dusty disks could finally bring the theory of close binary evolution into line
with observation.