The Continuing Search for Evidence of Tidal Orbital Decay of Hot Jupiters

Abstract

Many of the known hot Jupiters are formally unstable to tidal orbital decay. The only hot Jupiter for which orbital decay has been directly detected is WASP-12, for which transit timing measurements spanning more than a decade have revealed that the orbital period is decreasing at a rate of dP/dt ≈ 10 −9 , corresponding to a reduced tidal quality factor of about 2 × 10 5 . Here, we present a compilation of transit-timing data for WASP-12 and eleven other systems which are especially favorable for detecting orbital decay: 19, 43, 72, 103, 114, and 122; HAT-P-23; HATS-18; and OGLE-TR-56. For most of these systems we present new data that extend the time baseline over which observations have been performed. None of the systems besides WASP-12 displays convincing evidence for period changes, with typical upper limits on dP/dt on the order of 10 −9 or 10 −10 , and lower limits on the reduced tidal quality factor on the order of 10 5 . One possible exception is WASP-19, which shows a statistically significant trend, although it may be a spurious effect of starspot activity. Further observations are encouraged.

Tidal dissipation in evolving low-mass and solar-type stars with predictions for planetary orbital decay

“…We will later evaluate how this estimate changes during stellar evolution for stars with radiation zones in the mass range 0.4-1.6 solar masses. Note that this estimate apparently agrees very closely with the value required to explain the inferred orbital decay rate of WASP-12b (Patra et al 2017(Patra et al , 2020;…”

“…WASP-12b: is a 1.4 M J planet orbiting a metal-rich F-star with 1.35-1.43 M ⊙ in 1.09 d (Hebb et al 2009). This planet was first detected to be undergoing possible tidally driven orbital decay by Maciejewski et al (2016), and this has since been confirmed by various subsequent studies (Patra et al 2017;Maciejewski et al 2018Maciejewski et al , 2020bYee et al 2020;Patra et al 2020), which are consistent with Q ′ ≈ 2 × 10 5 . Previous theoretical work on this system by Chernov et al (2017) and Weinberg et al (2017) indicated that the observed decay rate can be explained using gravity wave dissipation depending on the specific stellar model.…”

“…Based on our current understanding of convective damping of equilibrium tides, this mechanism provides a negligible contribution to planetary orbital decay on the main sequence. in transit arrival times have been either detected or constrained, following Patra et al (2020), or those in which future detection appears favourable. We report our predictions in Table C1,a sw e l l as the parameters and outputs in our representative stellar models used to fit each star.…”

“…Dissipation of gravity waves in radiative cores is probably responsible for driving orbital decay of hot Jupiters (Barker & Ogilvie 2010;B a r k e r2011; Chernov, Ivanov & Papaloizou 2017). Indeed, the resulting tidal dissipation can explain the observationally inferred orbital decay rate of WASP-12b (Maciejewski et al 2016;Patra et al 2017;Maciejewski et al 2018;Yee et al 2020;Patra et al 2020) MNRAS 498, 2270-2294 (2020) if the waves are fully damped (Chernov et al 2017;Weinberg et al 2017;Bailey & Goodman 2019). Whether or not these waves should be fully damped likely depends strongly on the structure of the star (and therefore its mass and age).…”

Simultaneous TESS and NGTS transit observations of WASP-166 b

“…The precise transit ephemerides achievable with this observing method will also allow NGTS to monitor the transit timing variations of shortperiod Jupiter-like planets to search for signs of orbital decay (e.g. Baluev et al 2019;Patra et al 2020;Yee et al 2020). In addition to measuring transit timing variations, the precise ephemerides achievable with NGTS multitelescope observations will also be of use for the scheduling of future transmission spectroscopic measurements, and other characterization efforts.…”