Spitzer Space Telescope - Archive Research Proposal #30689


A White Dwarf-Based Investigation of the IRAC Photometric Absolute
Calibration

Principal Investigator: Jay Holberg
           Institution: University of Ariziona

Co-Investigators: 
Pierre Bergeron, University of Montreal                               

Science Category: brown dwarfs/very low mass stars 
Dollars Approved: 55256.0 

Abstract:
We propose a SPITZER Archive Program to use the extensive set of DA
(pure hydrogen) white dwarfs in the SPITZER Science Archive to:  1)
perform an independent investigation of the absolute calibration of
the IRAC bands, 2) to evaluated the claim (Kilic et al.  2005) that
cool white dwarfs possess unexplained flux deficits in the IRAC 4.5
micron and 8 micron channels, and 3) to systematically investigate the
effects of Collisionally Induced Opacities and other opacity sources
in cool white dwarfs.  Our proposed data set consists primarily of the
large set of those DA white dwarfs which have been observed with IRAC,
AND which possess spectroscopically determined temperatures and
gravities.  These stars are placed on the HST photometric scale, with
its well defined links to Vega, to optical fluxes, and to the 2MASS
Near-IR bands.  Model atmosphere fluxes, precisely matching the
optical and 2MASS photometry and optical spectroscopy, are used to
predict the corresponding IRAC fluxes.  This procedure is demonstrated
for a set of published IRAC observations.