WASP-4b Arrived Early for the TESS Mission. (arXiv:1903.02573v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bouma_L/0/1/0/all/0/1">L. G. Bouma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Winn_J/0/1/0/all/0/1">J. N. Winn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Baxter_C/0/1/0/all/0/1">C. Baxter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bhatti_W/0/1/0/all/0/1">W. Bhatti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dai_F/0/1/0/all/0/1">F. Dai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Daylan_T/0/1/0/all/0/1">T. Daylan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Desert_J/0/1/0/all/0/1">J.-M. D&#xe9;sert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hill_M/0/1/0/all/0/1">M. L. Hill</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kane_S/0/1/0/all/0/1">S. R. Kane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stassun_K/0/1/0/all/0/1">K. G. Stassun</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Villasenor_J/0/1/0/all/0/1">J. Villasenor</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ricker_G/0/1/0/all/0/1">G. R. Ricker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vanderspek_R/0/1/0/all/0/1">R. Vanderspek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Latham_D/0/1/0/all/0/1">D. W. Latham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Seager_S/0/1/0/all/0/1">S. Seager</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jenkins_J/0/1/0/all/0/1">J. M. Jenkins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berta_Thompson_Z/0/1/0/all/0/1">Z. Berta-Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Colon_K/0/1/0/all/0/1">K. Col&#xf3;n</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fausnaugh_M/0/1/0/all/0/1">M. Fausnaugh</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:+Guerrero_N/0/1/0/all/0/1">N. Guerrero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodriguez_J/0/1/0/all/0/1">J. E. Rodriguez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Twicken_J/0/1/0/all/0/1">J. D. Twicken</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wohler_B/0/1/0/all/0/1">B. Wohler</a>

The Transiting Exoplanet Survey Satellite (TESS) recently observed 18
transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6
$pm$ 11.7 seconds earlier than had been predicted, based on data stretching
back to 2007. This is unlikely to be the result of a clock error, because TESS
observations of other hot Jupiters (WASP-6b, 18b, and 46b) are compatible with
a constant period, ruling out an 81.6-second offset at the 6.4$sigma$ level.
The 1.3-day orbital period of WASP-4b appears to be decreasing at a rate of
$dot{P} = -12.6 pm 1.2$ milliseconds per year. The apparent period change
might be caused by tidal orbital decay or apsidal precession, although both
interpretations have shortcomings. The gravitational influence of a third body
is another possibility, though at present there is minimal evidence for such a
body. Further observations are needed to confirm and understand the timing
variation.

The Transiting Exoplanet Survey Satellite (TESS) recently observed 18
transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6
$pm$ 11.7 seconds earlier than had been predicted, based on data stretching
back to 2007. This is unlikely to be the result of a clock error, because TESS
observations of other hot Jupiters (WASP-6b, 18b, and 46b) are compatible with
a constant period, ruling out an 81.6-second offset at the 6.4$sigma$ level.
The 1.3-day orbital period of WASP-4b appears to be decreasing at a rate of
$dot{P} = -12.6 pm 1.2$ milliseconds per year. The apparent period change
might be caused by tidal orbital decay or apsidal precession, although both
interpretations have shortcomings. The gravitational influence of a third body
is another possibility, though at present there is minimal evidence for such a
body. Further observations are needed to confirm and understand the timing
variation.

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