Low albedos of hot to ultra-hot Jupiters in the optical to near-infrared transition regime. (arXiv:1902.07944v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Mallonn_M/0/1/0/all/0/1">M. Mallonn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kohler_J/0/1/0/all/0/1">J. K&#xf6;hler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alexoudi_X/0/1/0/all/0/1">X. Alexoudi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Essen_C/0/1/0/all/0/1">C. von Essen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Granzer_T/0/1/0/all/0/1">T. Granzer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Poppenhaeger_K/0/1/0/all/0/1">K. Poppenhaeger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Strassmeier_K/0/1/0/all/0/1">K.G. Strassmeier</a>

The depth of a secondary eclipse contains information of both the thermally
emitted light component of a hot Jupiter and the reflected light component. If
the dayside atmosphere of the planet is assumed to be isothermal, it is
possible to disentangle both. In this work, we analyze 11 eclipse light curves
of the hot Jupiter HAT-P-32b obtained at 0.89 $mu$m in the z’ band. We obtain
a null detection for the eclipse depth with state-of-the-art precision, -0.01
+- 0.10 ppt. We confirm previous studies showing that a non-inverted atmosphere
model is in disagreement to the measured emission spectrum of HAT-P-32b. We
derive an upper limit on the reflected light component, and thus, on the
planetary geometric albedo $A_g$. The 97.5%-confidence upper limit is $A_g$ < 0.2. This is the first albedo constraint for HAT-P-32b, and the first z' band albedo value for any exoplanet. It disfavors the influence of large-sized silicate condensates on the planetary day side. We inferred z' band geometric albedo limits from published eclipse measurements also for the ultra-hot Jupiters WASP-12b, WASP-19b, WASP-103b, and WASP-121b, applying the same method. These values consistently point to a low reflectivity in the optical to near-infrared transition regime for hot to ultra-hot Jupiters.

The depth of a secondary eclipse contains information of both the thermally
emitted light component of a hot Jupiter and the reflected light component. If
the dayside atmosphere of the planet is assumed to be isothermal, it is
possible to disentangle both. In this work, we analyze 11 eclipse light curves
of the hot Jupiter HAT-P-32b obtained at 0.89 $mu$m in the z’ band. We obtain
a null detection for the eclipse depth with state-of-the-art precision, -0.01
+- 0.10 ppt. We confirm previous studies showing that a non-inverted atmosphere
model is in disagreement to the measured emission spectrum of HAT-P-32b. We
derive an upper limit on the reflected light component, and thus, on the
planetary geometric albedo $A_g$. The 97.5%-confidence upper limit is $A_g$ <
0.2. This is the first albedo constraint for HAT-P-32b, and the first z’ band
albedo value for any exoplanet. It disfavors the influence of large-sized
silicate condensates on the planetary day side. We inferred z’ band geometric
albedo limits from published eclipse measurements also for the ultra-hot
Jupiters WASP-12b, WASP-19b, WASP-103b, and WASP-121b, applying the same
method. These values consistently point to a low reflectivity in the optical to
near-infrared transition regime for hot to ultra-hot Jupiters.

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