Hot Jupiter HAT-P-13b's Core is Probably 11 Earth Mass

Dynamical Constraints on the Core Mass of Hot Jupiter HAT-P-13b

Authors:

Buhler et al

Abstract:

HAT-P-13b is a Jupiter-mass transiting exoplanet that has settled onto a stable, short-period, and mildly eccentric orbit as a consequence of the action of tidal dissipation and perturbations from a second, highly eccentric, outer companion. Due to the special orbital configuration of the HAT-P-13 system, the magnitude of HAT-P-13b's eccentricity (eb) is in part dictated by its Love number (k2b), which is in turn a proxy for the degree of central mass concentration in its interior. Thus, the measurement of eb constrains k2b and allows us to place otherwise elusive constraints on the mass of HAT-P-13b's core (Mcore,b). In this study we derive new constraints on the value of eb by observing two secondary eclipses of HAT-P-13b with the Infrared Array Camera on board the Spitzer Space Telescope. We fit the measured secondary eclipse times simultaneously with radial velocity measurements and find that eb=0.00700±0.00100. We then use octupole-order secular perturbation theory to find the corresponding k2b=0.31+0.08−0.05. Applying structural evolution models, we then find, with 68\% confidence, that Mcore,b is less than 25 Earth masses (M⊕). The most likely value of Mcore,b=11M⊕, which is similar to the core mass theoretically required for runaway gas accretion. This is the tightest constraint to date on the core mass of a hot Jupiter. Additionally, we find that the measured secondary eclipse depths, which are in the 3.6 μm and 4.5 μm bands, best match atmospheric model predictions with a dayside temperature inversion and relatively efficient day-night circulation.

More Details of HAT-P-12b, HAT-P-13b, HAT-P-16b, HAT-P-23b and WASP-10b

Exoplanet Transits Registered at the Universidad de Monterrey Observatory. Part I: HAT-P-12b, HAT-P-13b, HAT-P-16b, HAT-P-23b and WASP-10b

Authors:

Sada et al

Abstract:

Forty transits of the exoplanets HAT-P-12b, HAT-P-13b, HAT-P-16b, HAT-P-23b and WASP-10b were recorded with the 0.36m telescope at the Universidad de Monterrey Observatory. The images were captured with a standard Johnson-Cousins Rc and Ic and Sloan z' filters and processed to obtain individual light curves of the events. These light curves were successfully combined for each system to obtain a resulting one of higher quality, but with a slightly larger time sampling rate. A reduction by a factor of about four in per-point scatter was typically achieved, resulting in combined light curves with a scatter of ~1 mmag. The noise characteristics of the combined light curves were verified by comparing Allan variance plots of the residuals. The combined light curves for each system, along with radial velocity measurements from the literature when available, were modeled using a Monte Carlo method to obtain the essential parameters that characterize the systems. Our results for all these systems confirm the derived transit parameters (the planet-to-star radius ratio, Rp/R*; the scaled semi-major axis, a/R*; the orbital inclination, i; in some cases the eccentricity, e; and argument of periastron of the orbit, {\omega}), validating the methodology. This technique can be used by small college observatories equipped with modest-sized telescopes to help characterize known extrasolar planet systems. In some instances, the uncertainties of the essential transit parameters are also reduced. For HAT-P-23b, in particular, we derive a planet size 4.5 +- 1.0% smaller. We also derive improved linear periods for each system, useful for scheduling observations.