Stellar tidal-dissipation timescale and modified quality factor

Determine the tidal-decay timescale and effective modified stellar tidal quality factor for hot Jupiters as functions of planetary mass, orbital period, and host-star internal structure.

Background

The timescale on which stellar tides shrink a hot Jupiter’s orbit determines whether the planet can be engulfed during the host star’s main-sequence lifetime. The paper emphasizes that the effective modified tidal quality factor is commonly treated as fixed in observational work, even though tidal theory predicts dependence on planetary and stellar properties. The physical mechanisms governing stellar tidal dissipation therefore remain insufficiently constrained.

References

Hence, although the ``fast tides suppression'' scenario is compatible with the solution 1 in its value of $\chi_\tau$, future work should investigate whether it can also produce a consistent value of $P_\mathrm{mig}$.

— Constraining Tidal Migration with the Hot Jupiter Population  (2609.10850 - Ma et al., 9 Sep 2026) in Section 5.1, “Tidal Migration Theories”

If this is the case, the individual migration rates measured may not constrain the time-averaged solutions well because it is hard to know whether the planets are on resonances or not.

— Constraining Tidal Migration with the Hot Jupiter Population  (2609.10850 - Ma et al., 9 Sep 2026) in Section 5.3, “Constraints from Individual Systems”

Nevertheless, the timescale of such tidal decay, or equivalently the (effective) ``modified tidal quality factor" of the star, $Q'*$, defined as the quality factor $Q\star$ divided by $2/3$ of the Love number $k_2$ \citep{goldreich1966solar}, remains highly uncertain due to our poor understanding of the tidal dissipation mechanisms within stars.

— Are Hot Jupiters Tidally Disrupted During Stellar Main Sequence?  (2608.12790 - Hu et al., 13 Aug 2026) in Section 1, Introduction

These comparisons cannot yet identify a preferred tidal model because the simulations start from different populations and use different parameters. Different tidal models can also reproduce the HJ period distribution, depending on how and when HJs form \citep{Ma2026}. A stronger test would use the same initial population and compare the predicted obliquities, stellar rotation rates, planet masses, and orbital separations with observations.

— Stellar companions sculpt hot Jupiter formation and spin-orbit evolution  (2609.19249 - Shariat et al., 16 Sep 2026) in Section 5.7, paragraph beginning “Most tidal models broadly reproduce”

However, do these two examples shift the correct circularization period to the values below 1 day? Therefore, are the circularization theories incorrect, or badly parametrized? We do not think so. The reason is the following. Having only two cases is still only weak evidence and low-number statistics for any reliable conclusions.

— Are there really some eccentric eclipsing binaries having orbital periods below 1 d?  (2609.26036 - Zasche et al., 22 Sep 2026) in Section Conclusions

WASP-12 b's orbit is decaying, for unknown reasons.

— The Mysterious Inspiral of WASP-12b: Why Obliquity Tides Cannot Drive Orbital Decay  (2609.11925 - Lammers et al., 10 Sep 2026) in Abstract; Section 1, Introduction