Spitzer Space Telescope - General Observer Proposal #3655


Searching the Stellar Graveyard for Planets and Brown Dwarfs with SST

Principal Investigator: John Debes
           Institution: Pennsylvania State University

Co-Investigators: 
Steinn Sigurdsson, Penn State University                              

Science Category: compact objects 
 Observing Modes: IracMap 
  Hours Approved: 9.7 

Abstract:
We propose a small observing program to search nearby hydrogen white
dwarfs with metal lines (DAZs) for mid-IR excesses due to dusty disks
or substellar companions.  At first glance White Dwarfs (WDs) seem to
be an unlikely population to search for planets and substellar
objects, but recent theoretical and observational research predicts
that DAZs are markers for substellar systems and dusty disks.  WDs
then become an ideal target for ``forensic planetology'', we can infer
aspects of planet formation from these ``dead'' systems that span a
large range of initial stellar mass.  These considerations have
motivated us to propose for high contrast imaging searches for faint
companions to DAZs in the near-IR with NICMOS on HST.  IRAC photometry
on SST ideally complements a high spatial resolution search, both by
confirming candidate substellar objects already detected by our HST
program and by probing deeper at unresolved distances through the
detection of mid-IR excesses due to substellar companions.  We
estimate that 15 M$_{jup}$ companions will be able to be detected as
unresolved excesses, and 5-7$M_{jup}$ companions will be able to be
detected at spatial separations $>$ 3arcsec.  Results from this
program will help our understanding of the brown dwarf desert, the
frequency and effects of common envelope evolution, planet formation
and evolution, and the fraction of stars with planets or habitable
planets.