Storms or Systematics? The changing secondary eclipse depth of WASP-12b. (arXiv:1904.01973v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hooton_M/0/1/0/all/0/1">Matthew J. Hooton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mooij_E/0/1/0/all/0/1">Ernst J. W. de Mooij</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Watson_C/0/1/0/all/0/1">Christopher A. Watson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gibson_N/0/1/0/all/0/1">Neale P. Gibson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Galindo_Guil_F/0/1/0/all/0/1">Francisco J. Galindo-Guil</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Clavero_R/0/1/0/all/0/1">Rosa Clavero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Merritt_S/0/1/0/all/0/1">Stephanie R. Merritt</a>
WASP-12b is one of the most well-studied transiting exoplanets, as its
highly-inflated radius and its 1.1 day orbit around a G0-type star make it an
excellent target for atmospheric categorisation through observation during its
secondary eclipse. We present two new secondary eclipse observations of
WASP-12b, acquired a year apart with the Wide Field Camera on the Isaac Newton
Telescope (INT) and the IO:O instrument on the Liverpool Telescope (LT). These
observations were conducted in the $i^prime$-band, a window expected to be
dominated by TiO features if present in appreciable quantities in the upper
atmosphere. We measured eclipse depths that disagree with each other by
$sim$3$sigma$ (0.97 $pm$ 0.14 mmag on the INT and 0.44 $pm$ 0.21 mmag on
the LT), a result that is mirrored in previous $z^prime$-band secondary
eclipse measurements for WASP-12b. We explore explanations for these
disagreements, including systematic errors and variable thermal emission in the
dayside atmosphere of WASP-12b caused by temperature changes of a few hundred
Kelvin: a possibility we cannot rule out from our analysis. Full-phase curves
observed with TESS and CHEOPS have the potential to detect similar atmospheric
variability for WASP-12b and other optimal targets, and a strategic,
multi-telescope approach to future ground-based secondary eclipse observations
is required to discriminate between explanations involving storms and
systematics.
WASP-12b is one of the most well-studied transiting exoplanets, as its
highly-inflated radius and its 1.1 day orbit around a G0-type star make it an
excellent target for atmospheric categorisation through observation during its
secondary eclipse. We present two new secondary eclipse observations of
WASP-12b, acquired a year apart with the Wide Field Camera on the Isaac Newton
Telescope (INT) and the IO:O instrument on the Liverpool Telescope (LT). These
observations were conducted in the $i^prime$-band, a window expected to be
dominated by TiO features if present in appreciable quantities in the upper
atmosphere. We measured eclipse depths that disagree with each other by
$sim$3$sigma$ (0.97 $pm$ 0.14 mmag on the INT and 0.44 $pm$ 0.21 mmag on
the LT), a result that is mirrored in previous $z^prime$-band secondary
eclipse measurements for WASP-12b. We explore explanations for these
disagreements, including systematic errors and variable thermal emission in the
dayside atmosphere of WASP-12b caused by temperature changes of a few hundred
Kelvin: a possibility we cannot rule out from our analysis. Full-phase curves
observed with TESS and CHEOPS have the potential to detect similar atmospheric
variability for WASP-12b and other optimal targets, and a strategic,
multi-telescope approach to future ground-based secondary eclipse observations
is required to discriminate between explanations involving storms and
systematics.
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