Spitzer Space Telescope - General Observer Proposal #60102


Two for the Show: Observing the Periastron Passages of HD 80606 b

Principal Investigator: Jonathan Langton
           Institution: UCO/Lick Observatory; University of California, Sa

     Technical Contact: Jonathan Langton, UCO/Lick Observatory; University of California, Sa

Co-Investigators: 
Gregory Laughlin, UCO/Lick Obs                                        
Drake Deming, NASA Goddard Space Flight Center                        
Nicolas Iro, NASA Goddard Space Flight Center                         
Daniel Kasen, UCO/Lick Observatory                                    

Science Category: extrasolar planets 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 84.3 

Abstract:
In Cycle 4, we observed a periastron passage of the eccentric giant HD 80606 b
in Spitzer's 8-micron IRAC band, obtaining evidence of rapid heating during
periastron, as well as discovering that the planet undergoes secondary eclipse
several hours prior to periastron. Here, we are proposing to follow up on this
success with observations of two near-term periastron passages in the 4.5 micron
band. These observations will yield a number of concrete benefits: 1.)
Measurement of the baseline flux of the planet at 4.5 microns will improve the
characterization of the pre-periastron luminosity of the planet, and will
thereby clarify the role of tidal dissipation in heating the planet, which will
in turn yield insight into the planetary structure. 2.) Measurements of the
secondary transit depth at 4.5 microns will give insight into the bolometric
temperature of the planet, providing important constraints on all hydrodynamical
models of exoplanet atmospheres. 3.) Measurement of the heating rate at 4.5
microns prior to periastron will improve knowledge of the infrared radiative
timescale, which forms an essential constraint on competing exoplanetary general
circulation models under development. If one has heating rates at both 4.5
microns and 8 microns, then the bulk energetics of the planet's infrared
photosphere are clearer than if one relies on a brightness temperature derived
from a single frequency. 4.) The 8-micron observations did not extend long
enough after the periastron passage to determine the cooling rate as the planet
recedes from its primary. Our proposed observations will run well past
periastron, which will allow a more accurate determination of the
post-periastron cooling rate, again providing vital constraints on both
hydrodynamical and radiative models of strongly irradiated exoplanetary
atmospheres. To achieve these goals, we are requesting 40 hours of observation
time for each of the two periastron passages that will occur in Cycle 6 -- a
total of 80 hours of observation time.