2026-06-28T22:19:46Zivo://CDS.VizieR/J/ApJ/706/7852026-05-19T14:25:37ZJ.ApJIVOAHAT-P-12 light curveWe 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+/-0.0000021d, transit epoch T_c_=2454419.19556+/-0.00020 (BJD), and transit duration 0.0974+/-0.0006d. The host star has a mass of 0.73+/-0.02M_{sun}_, radius of 0.70^+0.02^_-0.01_R_{sun}_, effective temperature 4650+/-60K, 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+/-0.012M_J_ and radius of 0.959^+0.029^_-0.021_R_J_ yielding a mean density of 0.295+/-0.025g/cm^3^. Comparing these observations with recent theoretical models, we find that HAT-P-12b is consistent with a ~1-4.5Gyr, mildly irradiated, H/He-dominated planet with a core mass M_C_<~10M_{earth}_.infrared-photometryvisible-astronomybroad-band-photometrymultiple-starssolar-system-planetsstellar-astronomyobservational-astronomysolar-system-astronomyhttps://dc.g-vo.org/rr/q/lp/custom/CDS.VizieR/J/ApJ/706/785http://doi.org/10.26093/cds/vizier.17060785https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/706/7852009ApJ...706..785Hhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/706/785Hartman 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.Sari P.CDS2012https://cds.unistra.fr/vizier-org/licences_vizier.htmlCDS support team <cds-question@unistra.fr>DatasetAstroObjectsastronomy