Spitzer Space Telescope - Archive Research Proposal #50465


Precise Ages for Debris Disk Stars via Gyrochronology

Principal Investigator: Sydney Barnes
           Institution: Lowell Observatory

     Technical Contact: Sydney Barnes, Lowell Observatory

Co-Investigators: 
Katherine Su, University of Arizona                                   
John Stansberry, University of Arizona                                
Gregory Henry, Tennessee State University                             

Science Category: circumstellar/debris disks 
Dollars Approved: 75000 

Abstract:
The Spitzer Space Telescope plays a leading role in identifying and
investigating debris disks around nearby stars. This work will constitute one of
its great scientific legacies. These debris disks are important because they
probe analogs of our planetary system, and they could help understand the
history of our own solar system. A key problem in assembling a picture of the
evolution of these debris disk systems is that their ages are poorly known
because sensitivity issues force us to work with field stars. There are two
kinds of ages that are used: isochrone, and chromospheric. Isochrone ages for
field stars have large errors (~100%), and furthermore, are biased oldward.
Chromospheric ages, although better when available, still have errors ~50% and
are also biased in certain ways, especially for F stars. As a result, not only
is it not possible to identify possible breaks in the f_d vs. t relationship or
the presence of individual events, but the decay relationship itself is known
very poorly. We propose to use the new technique of gryochronology to refine the
ages of a sample of ~50 field debris-disk host stars of solar-type.
Gyrochronology, using a star's rotation period and color, allows the
determination of the age of a field star to ~15-20%, a remarkable improvement in
precision over the isochrone and chromospheric ages. The required rotation
periods for the debris disk stars will be derived using an Automatic Photometric
Telescope to measure the rotational modulation caused by transits of starspots.
With accurate ages, we will be able to resolve LHB-like events if present,
measure the decay relationship well, or indeed show that such a relationship
does not generally hold.