Astrophys. J., 706, 785-796 (2009/November-3)
HAT-P-12b: a low-density sub-Saturn mass planet transiting a metal-poor K dwarf.
HARTMAN J.D., BAKOS G.A., TORRES G., KOVACS G., NOYES R.W., PAL A., LATHAM D.W., SIPOCZ B., FISCHER D.A., JOHNSON J.A., MARCY G.W., BUTLER R.P., HOWARD A.W., ESQUERDO G.A., SASSELOV D.D., KOVACS G., STEFANIK R.P., FERNANDEZ J.M., LAZAR J., PAPP I. and SARI P.
Abstract (from CDS):
We report on the discovery of HAT-P-12b, a transiting extrasolar planet orbiting the moderately bright V ~ 12.8 K4 dwarf GSC 03033-00706, with a period P = 3.2130598±0.0000021 d, transit epoch Tc= 2454419.19556 ±0.00020 (BJD), and transit duration 0.0974±0.0006 d. The host star has a mass of 0.73±0.02 M☉, radius of 0.70+0.02–0.01R☉, effective temperature 4650±60 K, and metallicity [Fe/H] = -0.29±0.05. We find a slight correlation between the observed spectral line bisector spans and the radial velocity, so we consider, and rule out, various blend configurations including a blend with a background eclipsing binary, and hierarchical triple systems where the eclipsing body is a star or a planet. We conclude that a model consisting of a single star with a transiting planet best fits the observations, and show that a likely explanation for the apparent correlation is contamination from scattered moonlight. Based on this model, the planetary companion has a mass of 0.211±0.012 MJ and radius of 0.959+0.029 –0.021RJ yielding a mean density of 0.295±0.025 g/cm3. Comparing these observations with recent theoretical models, we find that HAT-P-12b is consistent with a ∼1-4.5 Gyr, mildly irradiated, H/He-dominated planet with a core mass MC≲ 10 M⊕. HAT-P-12b is thus the least massive H/He-dominated gas giant planet found to date. This record was previously held by Saturn.
planetary systems - stars: individual (HAT-P-12, GSC 03033-00706) - techniques: photometric - techniques: spectroscopic
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<Available at CDS (J/ApJ/706/785): table2.dat>
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