Spitzer Space Telescope - Directors Discretionary Time Proposal #255


Spitzer Observations of a Newly-Discovered Nearly Edge-On Disk About
HD 32297

Principal Investigator: Glenn Schneider
           Institution: UNIVERSITY OF ARIZONA

Co-Investigators: 
Dean Hines, Space Science Institute                                   
Murray Silverstone, U. Arizona                                        
Thomas Henning, Max-Planck-Institut fur Astronomie, Heidelberg        
Sebastian Wolf, Max-Planck-Institut fur Astronomie, Heidelberg        
Francois Menard, Laboratoire d'Astrophysique                          
Carol Grady, Eureka Scientific                                        

Science Category: circumstellar/debris disks 
 Observing Modes: IracMap IrsStare MipsPhot 
  Hours Approved: 1.1 

Abstract:
We request 1.1 hours of Spitzer Director's Discretionary time to
obtain IRAC and MIPS imaging photometry and IRS low resolution
spectroscopy of a newly discovered, nearly edge-on, debris disk around
HD 32297.  The disk, discovered in our currently executing HST/NICMOS
GO 10177 coronagraphic survey program, extends at least 3.3" (400  AU)
from the star along its major axis and has a 1.1 micron flux density
of F(1.1 micron) = 4.81 +/- 0.57 mJy beyond 0.3".  Although providing
crucial information on the disk morphology and dust scattering
efficiency, our scattered light image cannot unambiguously inform on
the physical properties of the dust in this potentially planet-forming
environment.  Thermal emission from the disk was detected at 25 + 60
microns with IRAS, but these measures alone permit only a very
rudimentary thermal model of the system, leaving many degeneracies
that allow a large range of particle sizes and disk masses.  No other
IR photometry is available, and indeed this object has been largely
ignored in the past at all wavelengths.  To further elucidate the
physical characteristics of the disk and its constituent grains, we
propose to obtain photometry and spectra from 3.6 - 160  microns with
the Spitzer Space Telescope.  This will allow us to develop a
well-sampled spectral energy distribution (SED) for both the star and
the disk emission, including mid-IR spectral coverage sufficient to
characterize mineralogical features that will place strong constraints
on the dust constituents.  In addition, the large angular extent of
the disk makes it one of the few known systems that can be spatially
resolved in thermal emission with Spitzer (at wavelengths < 24
micron).  Given the 1.1 microns scattering fraction of f(disk)/f(star)
= 0.33% (from our NICMOS observations), an IRAS F(60  micron) = 1.12
Jy, and a 25 + 60  microns fractional dust emission excess luminosity
of L(ir)/L(star) ~ 0.27%, this object is easy to observe with Spitzer
and will consume minimal resources.  As one of only a small handful of
disks resolved