TESS full orbital phase curve of the WASP-18b system. (arXiv:1811.06020v1 [astro-ph.EP])

TESS full orbital phase curve of the WASP-18b system. (arXiv:1811.06020v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Shporer_A/0/1/0/all/0/1">Avi Shporer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wong_I/0/1/0/all/0/1">Ian Wong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huang_C/0/1/0/all/0/1">Chelsea X. Huang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Line_M/0/1/0/all/0/1">Michael R. Line</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stassun_K/0/1/0/all/0/1">Keivan G. Stassun</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fetherolf_T/0/1/0/all/0/1">Tara Fetherolf</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kane_S/0/1/0/all/0/1">Stephen Kane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ricker_G/0/1/0/all/0/1">George R. Ricker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Latham_D/0/1/0/all/0/1">David W. Latham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Seager_S/0/1/0/all/0/1">Sara Seager</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Winn_J/0/1/0/all/0/1">Joshua N. Winn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jenkins_J/0/1/0/all/0/1">Jon M. Jenkins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Glidden_A/0/1/0/all/0/1">Ana Glidden</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berta_Thompson_Z/0/1/0/all/0/1">Zach Berta-Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ting_E/0/1/0/all/0/1">Eric B. Ting</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_J/0/1/0/all/0/1">Jie Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haworth_K/0/1/0/all/0/1">Kari Haworth</a>

We present the full visible-light orbital phase curve of the transiting
planet WASP-18b measured by the TESS Mission. The phase curve includes the
transit, secondary eclipse, and sinusoidal modulations across the orbital phase
shaped by the planet’s atmospheric characteristics and the star-planet
gravitational interaction. We measure the beaming (Doppler boosting) and tidal
ellipsoidal distortion phase modulations and show that the amplitudes of both
agree with theoretical expectations. We find that the light from the planet’s
day side occulted during secondary eclipse, with a relative brightness of 355
$pm$ 21 ppm, is dominated by thermal emission, leading to an upper limit on
the geometric albedo in the TESS band of 0.057 (2 $sigma$). We also detect the
phase modulation due to the planet’s atmosphere longitudinal brightness
distribution. We find that its maximum is well-aligned with the sub-stellar
point, and we place an upper limit on the phase shift of 3.5 deg (2 $sigma$).
Finally, we do not detect light from the planet’s night-side hemisphere, with
an upper limit of 53 ppm (2 $sigma$), which is 15 % of the day-side
brightness. The low albedo, lack of atmospheric phase shift, and inefficient
heat distribution from the day to night hemispheres that we deduce from our
analysis are consistent with theoretical expectations and similar findings for
other strongly irradiated gas giant planets. This work demonstrates the
potential of TESS data for studying full orbital phase curves of transiting
systems.

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