Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userInflation of Migrated Hot Jupiters
105
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The observed low densities of gas giant planets with a high equilibrium temperature 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 disk 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%) show a significant radius discrepancy when the deposit is at higher pressures than P=1 bar. For a smaller fraction of 1%, 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.
rate research
Read More
We confirm the planetary nature of two transiting hot Jupiters discovered by the Kepler spacecrafts K2 extended mission in its Campaign 4, using precise radial velocity measurements from FIES@NOT, HARPS-N@TNG, and the coude spectrograph on the McDonald Observatory 2.7 m telescope. K2-29 b (EPIC 211089792 b) transits a K1V star with a period of $3.2589263pm0.0000015$ days; its orbit is slightly eccentric ($e=0.084_{-0.023}^{+0.032}$). It has a radius of $R_P=1.000_{-0.067}^{+0.071}$ $R_J$ and a mass of $M_P=0.613_{-0.026}^{+0.027}$ $M_J$. Its host star exhibits significant rotational variability, and we measure a rotation period of $P_{mathrm{rot}}=10.777 pm 0.031$ days. K2-30 b (EPIC 210957318 b) transits a G6V star with a period of $4.098503pm0.000011$ days. It has a radius of $R_P=1.039_{-0.051}^{+0.050}$ $R_J$ and a mass of $M_P=0.579_{-0.027}^{+0.028}$ $M_J$. The star has a low metallicity for a hot Jupiter host, $[mathrm{Fe}/mathrm{H}]=-0.15 pm 0.05$.
We determine the fraction of F, G, and K dwarfs in the Solar Neighborhood hosting hot jupiters as measured by the California Planet Survey from the Lick and Keck planet searches. We find the rate to be 1.2pm0.38%, which is consistent with the rate reported by Mayor et al. (2011) from the HARPS and CORALIE radial velocity surveys. These numbers are more than double the rate reported by Howard et al. (2011) for Kepler stars and the rate of Gould et al. (2006) from the OGLE-III transit search, however due to small number statistics these differences are of only marginal statistical significance. We explore some of the difficulties in estimating this rate from the existing radial velocity data sets and comparing radial velocity rates to rates from other techniques.
We use ground-based and space-based eclipse measurements for the near-infrared ($JHK!s$) bands and Spitzer 3.6 $mu$m and 4.5 $mu$m bands to construct colour-colour and colour-magnitude diagrams for hot Jupiters. We compare the results with previous observations of substellar objects and find that hot Jupiters, when corrected for their inflated radii, lie near the black body line and in the same region of the colour magnitude diagrams as brown dwarfs, including low gravity dwarfs that have been previously suggested as exoplanet analogs. We use theoretical emission spectra to investigate the effects of different metallicity, C/O ratios and temperatures on the IR colours. In general we find that while differences in C/O ratio and metallicity do correspond to different locations on these diagrams, the measurement errors are too large to use this method to put strong constraints on the composition of individual objects. However, as a class hot Jupiters cluster around the location expected for solar metallicity and C/O ratio.
Several authors have shown that precise measurements of transit time variations of exoplanets can be sensitive to other planetary bodies, such as exo-moons. In addition, the transit timing variations of the exoplanets closest to their host stars can provide tests of tidal dissipation theory. These studies, however, have not considered the effect of the host star. There is a large body of observational evidence that eclipse times of binary stars can vary dramatically due to variations in the quadrupole moment of the stars driven by stellar activity. In this paper we investigate and estimate the likely impact such variations have on the transit times of exoplanets. We find in several cases that such variations should be detectable. In particular, the estimated period changes for WASP-18b are of the same order as those expected for tidal dissipation, even for relatively low values of the tidal dissipation parameter. The transit time variations caused by the Applegate mechanism are also of the correct magnitude and occur on timescales such that they may be confused with variations caused by light-time travel effects due to the presence of a Jupiter-like second planet. Finally, we suggest that transiting exoplanet systems may provide a clean route (compared to binaries) to constraining the type of dynamo operating in the host star.
Evidence of star-planet interactions in the form of planet-modulated chromospheric emission has been noted for a number of hot Jupiters. Magnetic star-planet interactions involve the release of energy stored in the stellar and planetary magnetic fields. These signals thus offer indirect detections of exoplanetary magnetic fields. Here we report the derivation of the magnetic field strengths of four hot Jupiter systems using the power observed in Ca II K emission modulated by magnetic star-planet interactions. By approximating the fractional energy released in the Ca II K line we find that the surface magnetic field values for the hot Jupiters in our sample range from 20 G to 120 G, ~10-100 times larger than the values predicted by dynamo scaling laws for planets with rotation periods of ~2 - 4 days. On the other hand, these value are in agreement with scaling laws relating the magnetic field strength to the internal heat flux in giant planets. Large planetary magnetic field strengths may produce observable electron-cyclotron maser radio emission by preventing the maser from being quenched by the planets ionosphere. Intensive radio monitoring of hot Jupiter systems will help confirm these field values and inform on the generation mechanism of magnetic fields in this important class of exoplanets.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
