TY - JOUR
T1 - Statistical Characterization of Hot Jupiter Atmospheres Using Spitzer's Secondary Eclipses
AU - Garhart, Emily
AU - Deming, Drake
AU - Mandell, Avi
AU - Knutson, Heather A.
AU - Wallack, Nicole
AU - Burrows, Adam
AU - Fortney, Jonathan J.
AU - Hood, Callie
AU - Seay, Christopher
AU - Sing, David K.
AU - Benneke, Björn
AU - Fraine, Jonathan D.
AU - Kataria, Tiffany
AU - Lewis, Nikole
AU - Madhusudhan, Nikku
AU - McCullough, Peter
AU - Stevenson, Kevin B.
AU - Wakeford, Hannah
PY - 2020/4/1
Y1 - 2020/4/1
N2 - We report 78 secondary eclipse depths for a sample of 36 transiting hot
Jupiters observed at 3.6 and 4.5 μm using the Spitzer Space
Telescope. Our eclipse results for 27 of these planets are new, and
include highly irradiated worlds such as KELT-7b, WASP-87b, WASP-76b,
and WASP-64b, and important targets for James Webb Space Telescope such
as WASP-62b. We find that WASP-62b has a slightly eccentric orbit (
$e\cos \omega =0.00614\pm 0.00064 ), and we confirm the eccentricity of
HAT-P-13b and WASP-14b. The remainder are individually consistent with
circular orbits, but we find statistical evidence for eccentricity
increasing with orbital period in our range from 1 to 5 days. Our
day-side brightness temperatures for the planets yield information on
albedo and heat redistribution, following Cowan & Agol (2011).
Planets having maximum day-side temperatures exceeding ∼2200 K are
consistent with having zero albedo and a distribution of stellar
irradiance uniformly over the day-side hemisphere. Our most intriguing
result is that we detect a systematic difference between the emergent
spectra of these hot Jupiters as compared to blackbodies. The ratio of
observed brightness temperatures, Tb(4.5)/Tb(3.6), increases with
equilibrium temperature by 100 ± 24 parts-per-million per Kelvin,
over the entire temperature range in our sample (800-2500 K). No
existing model predicts this trend over such a large range of
temperature. We suggest that this may be due to a structural difference
in the atmospheric temperature profiles of real planetary atmospheres as
compared to models.
AB - We report 78 secondary eclipse depths for a sample of 36 transiting hot
Jupiters observed at 3.6 and 4.5 μm using the Spitzer Space
Telescope. Our eclipse results for 27 of these planets are new, and
include highly irradiated worlds such as KELT-7b, WASP-87b, WASP-76b,
and WASP-64b, and important targets for James Webb Space Telescope such
as WASP-62b. We find that WASP-62b has a slightly eccentric orbit (
$e\cos \omega =0.00614\pm 0.00064 ), and we confirm the eccentricity of
HAT-P-13b and WASP-14b. The remainder are individually consistent with
circular orbits, but we find statistical evidence for eccentricity
increasing with orbital period in our range from 1 to 5 days. Our
day-side brightness temperatures for the planets yield information on
albedo and heat redistribution, following Cowan & Agol (2011).
Planets having maximum day-side temperatures exceeding ∼2200 K are
consistent with having zero albedo and a distribution of stellar
irradiance uniformly over the day-side hemisphere. Our most intriguing
result is that we detect a systematic difference between the emergent
spectra of these hot Jupiters as compared to blackbodies. The ratio of
observed brightness temperatures, Tb(4.5)/Tb(3.6), increases with
equilibrium temperature by 100 ± 24 parts-per-million per Kelvin,
over the entire temperature range in our sample (800-2500 K). No
existing model predicts this trend over such a large range of
temperature. We suggest that this may be due to a structural difference
in the atmospheric temperature profiles of real planetary atmospheres as
compared to models.
U2 - 10.3847/1538-3881/ab6cff
DO - 10.3847/1538-3881/ab6cff
M3 - Article (Academic Journal)
SN - 0004-6256
VL - 159
SP - 137
JO - Astronomical Journal
JF - Astronomical Journal
IS - 4
ER -