HAT-P-19b orbits around V = 12.901 K1 dwarf star GSC 2.283-00.589, with a period P=4.008778 + -0.000006 d, transit epoch Tc= -0.00034 2.455.091.53417+ (BJD), and transit duration 0.1182 -0.0014 + d. The central star has a mass of 0.84 solar masses + -0.04, radius of 0.82 + -0.05 Rsun, the effective temperature of 4990 K + -130, and metallicity [Fe / H] = + 0.23 + -0.08. The planetary companion has a mass of 0.292 -0.018 + Mjup, and the radius of 1.132 -0.072 + Rjup producing an average density of 0.25 + -0.04 g cm-3.
Radial velocity data for HAT-P-19 exhibit a linear trend over time, indicating the presence of a third body in the system. When comparing these observations with theoretical models, we find that HAT-P-18b and HAT-P-19b are consistent with giant planets dominated by hydrogen and helium, with the mass of the nucleus negligible.
HAT-P-18b and HAT-P-19b join HAT-P-12b and WASP-21b into an emerging group of low-density Planets-Saturn, with negligible base masses. However, unlike HAT-P-12b and WASP-21b, both HAT-P-18b and HAT-P-19b orbit stars with super-solar metallicity. This calls into question the hitherto suggestive correlation between the mass of the inferred core and the metallicity of the host star on planets with the Saturn-mass.
https://arxiv.org/abs/1007.4850
Observations of HAT-P-19b
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