Abstract
ABSTRACT The observed low densities of gas giant planets with a high equilibrium temperature (hot Jupiters) can be simulated in models when a fraction of the surface radiation is deposited deeper in the interior. Meanwhile, migration theories suggest that hot Jupiters formed further away from their host star and migrated inward. We incorporate disc migration in simulations of the evolving interior of hot Jupiters to determine whether migration has a long-lasting effect on the inflation of planets. We quantify the difference between the radius of a migrated planet and the radius of a planet that formed in situ as the radius discrepancy. We remain agnostic about the physical mechanism behind interior heating, but assume it scales with the received stellar flux by a certain fraction. We find that the change in irradiation received from the host star while the planet is migrating can affect the inflation and final radius of the planet. Models with a high fraction of energy deposited in the interior (>5 per cent) show a significant radius discrepancy when the deposit is at higher pressures than $P=1 \, \mathrm{bar}$. For a smaller fraction of 1 per cent, there is no radius discrepancy for any deposit depth. We show that a uniform heating mechanism can cause different rates of inflation, depending on the migration history. If the forthcoming observations on mean densities and atmospheres of gas giants give a better indication of a potential heating mechanism, this could help to constrain the prior migration of such planets.
Highlights
In the last 25 years we have seen the hot Jupiter grow from one anomalous discovery into a distinct population of detected exoplanets
We show that in the case of an interior heating mechanism which is strongly related to the incident flux, migration will influence the degree of inflation
Our models explore different migration timescales, take a stellar flux into account that varies with time and consider different inflation mechanisms by adding extra energy at different pressures in the planet interior
Summary
In the last 25 years we have seen the hot Jupiter grow from one anomalous discovery into a distinct population of detected exoplanets In this timespan they have taken up an important role in exoplanet science. Because they are massive planets at short periods, they are relatively easier to detect by radial velocity and transit photometry, making this a big population. One unexplained observed feature of hot Jupiters is their inflation Their measured density is lower than simulations can reproduce, even when surface radiation from the host star is considered. Simulations of hot Jupiters start with a high-entropy, inflated planet During the evolution this inflation is expected to recede as the planet looses it’s formation heat by cooling and contracting. In order to reproduce inflation of hot Jupiters, alternative or additional physical mechanisms need
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