Dynamical Constraints on the Core Mass of Hot Jupiter HATP13b
Abstract
HATP13b is a Jupitermass transiting exoplanet that has settled onto a stable, shortperiod, and mildly eccentric orbit as a consequence of the action of tidal dissipation and perturbations from a second, highly eccentric, outer companion. Owing to the special orbital configuration of the HATP13 system, the magnitude of HATP13b's eccentricity (e_{b}) is in part dictated by its Love number ({k}_{{2}_{b}}), which is in turn a proxy for the degree of central mass concentration in its interior. Thus, the measurement of e_{b} constrains {k}_{{2}_{b}} and allows us to place otherwise elusive constraints on the mass of HATP13b's core (M_{core,b}). In this study we derive new constraints on the value of e_{b} by observing two secondary eclipses of HATP13b 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 e_{b} = 0.00700 ± 0.00100. We then use octupoleorder secular perturbation theory to find the corresponding {k}_{{2}_{b}}={0.31}_{0.05}^{+0.08}. Applying structural evolution models, we then find, with 68% confidence, that M_{core,b} is less than 25 Earth masses (M_{⊕}). The most likely value is M_{core,b} = 11 M_{⊕}, 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 and 4.5 μm bands, best match atmospheric model predictions with a dayside temperature inversion and relatively efficient daynight circulation.
 Publication:

The Astrophysical Journal
 Pub Date:
 April 2016
 DOI:
 10.3847/0004637X/821/1/26
 arXiv:
 arXiv:1602.03895
 Bibcode:
 2016ApJ...821...26B
 Keywords:

 methods: data analysis;
 planets and satellites: atmospheres;
 planets and satellites: dynamical evolution and stability;
 planets and satellites: individual: HATP13b;
 planets and satellites: interiors;
 techniques: photometric;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 12 pages, 5 figures, 1 table, Accepted to ApJ on February 10, 2016